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POSTCONF(5)		      File Formats Manual		   POSTCONF(5)

NAME
       postconf	- Postfix configuration	parameters

SYNOPSIS
       postconf	parameter ...

       postconf	-e "parameter=value" ...

DESCRIPTION
       The  Postfix  main.cf configuration file	specifies parameters that con-
       trol the	operation of the Postfix mail system. Typically	the file  con-
       tains  only  a small subset of all parameters; parameters not specified
       are left	at their default values.

       The general format of the main.cf file is as follows:

       o      Each logical line	has the	form "parameter	= value".   Whitespace
	      around the "=" is	ignored, as is whitespace at the end of	a log-
	      ical line.

       o      Empty lines and whitespace-only lines are	ignored, as are	 lines
	      whose first non-whitespace character is a	`#'.

       o      A	 logical  line	starts	with  non-whitespace text. A line that
	      starts with whitespace continues a logical line.

       o      A	parameter value	may refer to other parameters.

	      o	     The expressions "$name" and "${name}" are recursively re-
		     placed with the value of the named	parameter. The parame-
		     ter name must contain only	characters from	the set	[a-zA-
		     Z0-9_]. An	undefined parameter value is replaced with the
		     empty value.

	      o	     The expressions "${name?value}" and "${name?{value}}" are
		     replaced  with "value" when "$name" is non-empty. The pa-
		     rameter name must contain only characters	from  the  set
		     [a-zA-Z0-9_]. These forms are supported with Postfix ver-
		     sions >= 2.2 and >= 3.0, respectively.

	      o	     The expressions "${name:value}" and "${name:{value}}" are
		     replaced  with "value" when "$name" is empty. The parame-
		     ter name must contain only	characters from	the set	[a-zA-
		     Z0-9_].  These  forms are supported with Postfix versions
		     >=	2.2 and	>= 3.0,	respectively.

	      o	     The expression  "${name?{value1}:{value2}}"  is  replaced
		     with   "value1"  when  "$name"  is	 non-empty,  and  with
		     "value2" when "$name" is empty.  The "{}" is required for
		     "value1",	optional for "value2". The parameter name must
		     contain only characters from the set [a-zA-Z0-9_].	  This
		     form is supported with Postfix versions >=	3.0.

	      o	     The  first	 item  inside "${...}" may be a	relational ex-
		     pression of the form: "{value3} ==	{value4}". Besides the
		     "=="  (equality) operator Postfix supports	"!=" (inequal-
		     ity), "<",	"<=", ">=", and	">". The comparison is numeri-
		     cal when both operands are	all digits, otherwise the com-
		     parison is	lexicographical.  These	 forms	are  supported
		     with Postfix versions >= 3.0.

	      o	     Each  "value" is subject to recursive named parameter and
		     relational	expression evaluation, except where noted.

	      o	     Whitespace	before or after	each "{value}" is ignored.

	      o	     Specify "$$" to produce a single "$" character.

	      o	     The legacy	form "$(...)" is equivalent to	the  preferred
		     form "${...}".

       o      When the same parameter is defined multiple times, only the last
	      instance is remembered.

       o      Otherwise, the order of main.cf parameter	definitions  does  not
	      matter.

       The remainder of	this document is a description of all Postfix configu-
       ration parameters. Default values are shown after the parameter name in
       parentheses, and	can be looked up with the "postconf -d"	command.

       Note:  this  is not an invitation to make changes to Postfix configura-
       tion parameters.	Unnecessary changes can	impair the  operation  of  the
       mail system.

2bounce_notice_recipient (default: postmaster)
       The  recipient  of  undeliverable  mail	that cannot be returned	to the
       sender.	This feature is	enabled	with the notify_classes	parameter.

access_map_defer_code (default:	450)
       The numerical Postfix SMTP server response code for  an	access(5)  map
       "defer" action, including "defer_if_permit" or "defer_if_reject". Prior
       to Postfix 2.6, the response is hard-coded as "450".

       Do not change this unless you have  a  complete	understanding  of  RFC
       5321.

       This feature is available in Postfix 2.6	and later.

access_map_reject_code (default: 554)
       The  numerical  Postfix	SMTP server response code for an access(5) map
       "reject"	action.

       Do not change this unless you have  a  complete	understanding  of  RFC
       5321.

address_verify_cache_cleanup_interval (default:	12h)
       The  amount  of	time  between  verify(8) address verification database
       cleanup runs. This feature requires  that  the  database	 supports  the
       "delete"	 and "sequence"	operators.  Specify a zero interval to disable
       database	cleanup.

       After each database cleanup run,	the verify(8) daemon logs  the	number
       of  entries  that were retained and dropped. A cleanup run is logged as
       "partial" when the daemon  terminates  early  after  "postfix  reload",
       "postfix	stop", or no requests for $max_idle seconds.

       Specify	a  non-negative	time value (an integral	value plus an optional
       one-letter suffix that specifies	the time unit).	 Time units:  s	 (sec-
       onds),  m  (minutes), h (hours),	d (days), w (weeks).  The default time
       unit is h (hours).

       This feature is available in Postfix 2.7.

address_verify_default_transport (default: $default_transport)
       Overrides the default_transport parameter setting for address verifica-
       tion probes.

       This feature is available in Postfix 2.1	and later.

address_verify_local_transport (default: $local_transport)
       Overrides  the  local_transport parameter setting for address verifica-
       tion probes.

       This feature is available in Postfix 2.1	and later.

address_verify_map (default: see postconf -d output)
       Lookup table for	persistent address verification	status	storage.   The
       table  is maintained by the verify(8) service, and is opened before the
       process releases	privileges.

       The lookup table	is persistent by  default  (Postfix  2.7  and  later).
       Specify	an empty table name to keep the	information in volatile	memory
       which is	lost after "postfix reload" or "postfix	stop". This is the de-
       fault with Postfix version 2.6 and earlier.

       Specify a location in a file system that	will not fill up. If the data-
       base becomes corrupted, the world comes to an end. To  recover,	delete
       (NOT: truncate) the file	and do "postfix	reload".

       Postfix	daemon	processes do not use root privileges when opening this
       file (Postfix 2.5 and later).  The file must therefore be stored	 under
       a  Postfix-owned	 directory such	as the data_directory.	As a migration
       aid, an attempt to open the file	under a	non-Postfix directory is redi-
       rected to the Postfix-owned data_directory, and a warning is logged.

       Examples:

       address_verify_map = hash:/var/lib/postfix/verify
       address_verify_map = btree:/var/lib/postfix/verify

       This feature is available in Postfix 2.1	and later.

address_verify_negative_cache (default:	yes)
       Enable caching of failed	address	verification probe results.  When this
       feature is enabled, the cache may pollute quickly with  garbage.	  When
       this  feature  is  disabled, Postfix will generate an address probe for
       every lookup.

       This feature is available in Postfix 2.1	and later.

address_verify_negative_expire_time (default: 3d)
       The time	after which a failed probe expires from	the address  verifica-
       tion cache.

       Specify	a  non-zero  time  value  (an  integral	value plus an optional
       one-letter suffix that specifies	the time unit).	 Time units:  s	 (sec-
       onds),  m  (minutes), h (hours),	d (days), w (weeks).  The default time
       unit is d (days).

       This feature is available in Postfix 2.1	and later.

address_verify_negative_refresh_time (default: 3h)
       The time	after which a failed address verification probe	 needs	to  be
       refreshed.

       Specify	a  non-zero  time  value  (an  integral	value plus an optional
       one-letter suffix that specifies	the time unit).	 Time units:  s	 (sec-
       onds),  m  (minutes), h (hours),	d (days), w (weeks).  The default time
       unit is h (hours).

       This feature is available in Postfix 2.1	and later.

address_verify_pending_request_limit (default: see postconf -d output)
       A safety	limit that prevents address verification requests  from	 over-
       whelming	 the Postfix queue. By default,	the number of pending requests
       is limited to 1/4 of the	active queue  maximum  size  (qmgr_message_ac-
       tive_limit).  The  queue	 manager enforces the limit by tempfailing re-
       quests that exceed the limit. This affects only unknown	addresses  and
       inactive	 addresses that	have expired, because the verify(8) daemon au-
       tomatically refreshes an	active address before it expires.

       This feature is available in Postfix 3.1	and later.

address_verify_poll_count (default: normal: 3, overload: 1)
       How many	times to query the verify(8) service for the completion	of  an
       address verification request in progress.

       By  default,  the Postfix SMTP server polls the verify(8) service up to
       three times under non-overload conditions, and  only  once  when	 under
       overload.  With Postfix version 2.5 and earlier,	the SMTP server	always
       polls the verify(8) service up to three times by	default.

       Specify 1 to implement a	crude form of greylisting, that	is, always de-
       fer the first delivery request for a new	address.

       Examples:

       # Postfix <= 2.6	default
       address_verify_poll_count = 3
       # Poor man's greylisting
       address_verify_poll_count = 1

       This feature is available in Postfix 2.1	and later.

address_verify_poll_delay (default: 3s)
       The delay between queries for the completion of an address verification
       request in progress.

       The default polling delay is 3 seconds.

       Specify a non-zero time value  (an  integral  value  plus  an  optional
       one-letter  suffix  that	specifies the time unit).  Time	units: s (sec-
       onds), m	(minutes), h (hours), d	(days),	w (weeks).  The	 default  time
       unit is s (seconds).

       This feature is available in Postfix 2.1	and later.

address_verify_positive_expire_time (default: 31d)
       The  time after which a successful probe	expires	from the address veri-
       fication	cache.

       Specify a non-zero time value  (an  integral  value  plus  an  optional
       one-letter  suffix  that	specifies the time unit).  Time	units: s (sec-
       onds), m	(minutes), h (hours), d	(days),	w (weeks).  The	 default  time
       unit is d (days).

       This feature is available in Postfix 2.1	and later.

address_verify_positive_refresh_time (default: 7d)
       The  time  after	which a	successful address verification	probe needs to
       be refreshed.  The address verification status is not updated when  the
       probe fails (optimistic caching).

       Specify	a  non-zero  time  value  (an  integral	value plus an optional
       one-letter suffix that specifies	the time unit).	 Time units:  s	 (sec-
       onds),  m  (minutes), h (hours),	d (days), w (weeks).  The default time
       unit is d (days).

       This feature is available in Postfix 2.1	and later.

address_verify_relay_transport (default: $relay_transport)
       Overrides the relay_transport parameter setting for  address  verifica-
       tion probes.

       This feature is available in Postfix 2.1	and later.

address_verify_relayhost (default: $relayhost)
       Overrides  the  relayhost  parameter  setting  for address verification
       probes. This information	can be overruled with the transport(5) table.

       This feature is available in Postfix 2.1	and later.

address_verify_sender (default:	$double_bounce_sender)
       The sender address to use in  address  verification  probes;  prior  to
       Postfix	2.5  the  default was "postmaster". To avoid problems with ad-
       dress probes that are sent in response to address probes,  the  Postfix
       SMTP  server  excludes  the  probe sender address from all SMTPD	access
       blocks.

       Specify an empty	value (address_verify_sender =)	or <> if you  want  to
       use  the	 null  sender address. Beware, some sites reject mail from <>,
       even though RFCs	require	that such addresses be accepted.

       Examples:

       address_verify_sender = <>
       address_verify_sender = postmaster@my.domain

       This feature is available in Postfix 2.1	and later.

address_verify_sender_dependent_default_transport_maps	(default:  $sender_de-
       pendent_default_transport_maps)
       Overrides the sender_dependent_default_transport_maps parameter setting
       for address verification	probes.

       This feature is available in Postfix 2.7	and later.

address_verify_sender_dependent_relayhost_maps (default: $sender_dependent_re-
       layhost_maps)
       Overrides the sender_dependent_relayhost_maps parameter setting for ad-
       dress verification probes.

       This feature is available in Postfix 2.3	and later.

address_verify_sender_ttl (default: 0s)
       The time	between	changes	in the time-dependent portion of address veri-
       fication	probe sender addresses.	The time-dependent portion is appended
       to the  localpart  of  the  address  specified  with  the  address_ver-
       ify_sender parameter. This feature is ignored when the probe sender ad-
       dresses is the null sender, i.e.	 the  address_verify_sender  value  is
       empty or	<>.

       Historically,  the probe	sender address was fixed. This has caused such
       addresses to end	up on spammer  mailing	lists,	and  has  resulted  in
       wasted network and processing resources.

       To  enable  time-dependent  probe  sender addresses, specify a non-zero
       time value. Specify a value of at least several hours, to  avoid	 prob-
       lems  with senders that use greylisting.	Avoid nice TTL values, to make
       the result less predictable.

       Specify a non-negative time value (an integral value plus  an  optional
       one-letter  suffix  that	specifies the time unit).  Time	units: s (sec-
       onds), m	(minutes), h (hours), d	(days),	w (weeks).  The	 default  time
       unit is s (seconds).

       This feature is available in Postfix 2.9	and later.

address_verify_service_name (default: verify)
       The  name  of  the verify(8) address verification service. This service
       maintains the status of sender and/or  recipient	 address  verification
       probes, and generates probes on request by other	Postfix	processes.

address_verify_transport_maps (default:	$transport_maps)
       Overrides the transport_maps parameter setting for address verification
       probes.

       This feature is available in Postfix 2.1	and later.

address_verify_virtual_transport (default: $virtual_transport)
       Overrides the virtual_transport parameter setting for address verifica-
       tion probes.

       This feature is available in Postfix 2.1	and later.

alias_database (default: see postconf -d output)
       The  alias  databases  for  local(8)  delivery  that  are  updated with
       "newaliases" or with "sendmail -bi".

       This is a separate configuration	parameter because not all  the	tables
       specified with $alias_maps have to be local files.

       Examples:

       alias_database =	hash:/etc/aliases
       alias_database =	hash:/etc/mail/aliases

alias_maps (default: see postconf -d output)
       The alias databases that	are used for local(8) delivery.	See aliases(5)
       for syntax details.  Specify zero or more  "type:name"  lookup  tables,
       separated by whitespace or comma. Tables	will be	searched in the	speci-
       fied order until	a match	is found.  Note: these lookups are recursive.

       The default list	is system dependent.  On systems with NIS, the default
       is to search the	local alias database, then the NIS alias database.

       If  you	change	the  alias  database, run "postalias /etc/aliases" (or
       wherever	your system  stores  the  mail	alias  file),  or  simply  run
       "newaliases" to build the necessary DBM or DB file.

       The  local(8)  delivery agent disallows regular expression substitution
       of $1 etc. in alias_maps, because that would open a security hole.

       The local(8) delivery agent will	silently ignore	requests  to  use  the
       proxymap(8)  server  within  alias_maps.	Instead	it will	open the table
       directly. Before	Postfix	version	2.2, the local(8) delivery agent  will
       terminate with a	fatal error.

       Examples:

       alias_maps = hash:/etc/aliases, nis:mail.aliases
       alias_maps = hash:/etc/aliases

allow_mail_to_commands (default: alias,	forward)
       Restrict	 local(8)  mail	delivery to external commands.	The default is
       to disallow delivery to "|command" in :include:	files (see  aliases(5)
       for the text that defines this terminology).

       Specify	zero  or more of: alias, forward or include, in	order to allow
       commands	in aliases(5), .forward	files or in :include:  files,  respec-
       tively.

       Example:

       allow_mail_to_commands =	alias,forward,include

allow_mail_to_files (default: alias, forward)
       Restrict	 local(8)  mail	 delivery to external files. The default is to
       disallow	"/file/name" destinations in :include:	files (see  aliases(5)
       for the text that defines this terminology).

       Specify	zero  or more of: alias, forward or include, in	order to allow
       "/file/name" destinations in aliases(5),	.forward  files	 and  in  :in-
       clude:  files, respectively.

       Example:

       allow_mail_to_files = alias,forward,include

allow_min_user (default: no)
       Allow a sender or recipient address to have `-' as the first character.
       By default, this	is not allowed,	to avoid accidents with	software  that
       passes email addresses via the command line. Such software would	not be
       able to distinguish a malicious address from a bona  fide  command-line
       option.	Although this can be prevented by inserting a "--" option ter-
       minator into the	command	line, this is  difficult  to  enforce  consis-
       tently and globally.

       As  of  Postfix version 2.5, this feature is implemented	by trivial-re-
       write(8).  With	earlier	 versions  this	 feature  was  implemented  by
       qmgr(8) and was limited to recipient addresses only.

allow_percent_hack (default: yes)
       Enable  the rewriting of	the form "user%domain" to "user@domain".  This
       is enabled by default.

       Note: as	of Postfix version 2.2,	message	header address rewriting  hap-
       pens only when one of the following conditions is true:

       o      The message is received with the Postfix sendmail(1) command,

       o      The  message is received from a network client that matches $lo-
	      cal_header_rewrite_clients,

       o      The  message  is	received  from	the  network,  and   the   re-
	      mote_header_rewrite_domain   parameter   specifies  a  non-empty
	      value.

       To  get	the  behavior  before  Postfix	version	 2.2,	specify	  "lo-
       cal_header_rewrite_clients = static:all".

       Example:

       allow_percent_hack = no

allow_untrusted_routing	(default: no)
       Forward	mail  with sender-specified routing (user[@%!]remote[@%!]site)
       from untrusted clients to destinations matching $relay_domains.

       By default, this	feature	is turned off.	This closes a nasty open relay
       loophole	 where	a  backup  MX host can be tricked into forwarding junk
       mail to a primary MX host which then spams it out to the	world.

       This parameter also controls if non-local addresses with	 sender-speci-
       fied  routing  can  match  Postfix  access tables. By default, such ad-
       dresses cannot match Postfix access tables, because the address is  am-
       biguous.

alternate_config_directories (default: empty)
       A  list	of  non-default	 Postfix configuration directories that	may be
       specified with "-c config_directory" on the command line	(in  the  case
       of  sendmail(1),	with the "-C" option), or via the MAIL_CONFIG environ-
       ment parameter.

       This list must be specified in the default Postfix  main.cf  file,  and
       will be used by set-gid Postfix commands	such as	postqueue(1) and post-
       drop(1).

       Specify absolute	pathnames, separated by	comma or  space.  Note:	 $name
       expansion is not	supported.

always_add_missing_headers (default: no)
       Always  add (Resent-) From:, To:, Date: or Message-ID: headers when not
       present.	 Postfix 2.6 and later add these  headers  only	 when  clients
       match  the  local_header_rewrite_clients	 parameter  setting.   Earlier
       Postfix versions	always add these headers; this may break  DKIM	signa-
       tures   that   cover  non-existent  headers.   The  undisclosed_recipi-
       ents_header parameter setting determines	whether	a To: header  will  be
       added.

always_bcc (default: empty)
       Optional	 address  that	receives a "blind carbon copy" of each message
       that is received	by the Postfix mail system.

       Note: with Postfix 2.3 and later	the BCC	address	is added as if it  was
       specified  with	NOTIFY=NONE.  The sender will not be notified when the
       BCC address is undeliverable, as	long as	all down-stream	 software  im-
       plements	RFC 3461.

       Note: with Postfix 2.2 and earlier the sender will be notified when the
       BCC address is undeliverable.

       Note: automatic BCC recipients are produced  only  for  new  mail.   To
       avoid  mailer  loops,  automatic	BCC recipients are not generated after
       Postfix forwards	mail internally, or after Postfix generates  mail  it-
       self.

anvil_rate_time_unit (default: 60s)
       The  time  unit	over which client connection rates and other rates are
       calculated.

       This feature is implemented by the anvil(8) service which is  available
       in Postfix version 2.2 and later.

       The default interval is relatively short. Because of the	high frequency
       of updates, the anvil(8)	server uses volatile memory only. Thus,	infor-
       mation is lost whenever the process terminates.

       Specify	a  non-zero  time  value  (an  integral	value plus an optional
       one-letter suffix that specifies	the time unit).	 Time units:  s	 (sec-
       onds),  m  (minutes), h (hours),	d (days), w (weeks).  The default time
       unit is s (seconds).

anvil_status_update_time (default: 600s)
       How frequently the anvil(8) connection and rate	limiting  server  logs
       peak usage information.

       Specify	a  non-zero  time  value  (an  integral	value plus an optional
       one-letter suffix that specifies	the time unit).	 Time units:  s	 (sec-
       onds),  m  (minutes), h (hours),	d (days), w (weeks).  The default time
       unit is s (seconds).

       This feature is available in Postfix 2.2	and later.

append_at_myorigin (default: yes)
       With locally submitted mail, append the string "@$myorigin" to mail ad-
       dresses	without	 domain	information. With remotely submitted mail, ap-
       pend the	string "@$remote_header_rewrite_domain"	instead.

       Note 1: this feature is enabled by default and must not be turned  off.
       Postfix does not	support	domain-less addresses.

       Note 2: with Postfix version 2.2, message header	address	rewriting hap-
       pens only when one of the following conditions is true:

       o      The message is received with the Postfix sendmail(1) command,

       o      The message is received from a network client that matches  $lo-
	      cal_header_rewrite_clients,

       o      The   message   is  received  from  the  network,	 and  the  re-
	      mote_header_rewrite_domain  parameter  specifies	 a   non-empty
	      value.

       To   get	  the  behavior	 before	 Postfix  version  2.2,	 specify  "lo-
       cal_header_rewrite_clients = static:all".

append_dot_mydomain (default: Postfix >= 3.0: no, Postfix < 3.0: yes)
       With locally submitted mail, append  the	 string	 ".$mydomain"  to  ad-
       dresses	that  have  no	".domain" information. With remotely submitted
       mail, append the	string ".$remote_header_rewrite_domain"	instead.

       Note 1: this feature is enabled by default. If disabled,	users will not
       be able to send mail to "user@partialdomainname"	but will have to spec-
       ify full	domain names instead.

       Note 2: with Postfix version 2.2, message header	address	rewriting hap-
       pens only when one of the following conditions is true:

       o      The message is received with the Postfix sendmail(1) command,

       o      The  message is received from a network client that matches $lo-
	      cal_header_rewrite_clients,

       o      The  message  is	received  from	the  network,  and   the   re-
	      mote_header_rewrite_domain   parameter   specifies  a  non-empty
	      value.

       To  get	the  behavior  before  Postfix	version	 2.2,	specify	  "lo-
       cal_header_rewrite_clients = static:all".

application_event_drain_time (default: 100s)
       How long	the postkick(1)	command	waits for a request to enter the Post-
       fix daemon process input	buffer before giving up.

       Specify a non-zero time value  (an  integral  value  plus  an  optional
       one-letter  suffix  that	specifies the time unit).  Time	units: s (sec-
       onds), m	(minutes), h (hours), d	(days),	w (weeks).  The	 default  time
       unit is s (seconds).

       This feature is available in Postfix 2.1	and later.

authorized_flush_users (default: static:anyone)
       List of users who are authorized	to flush the queue.

       By default, all users are allowed to flush the queue.  Access is	always
       granted if the invoking user is the super-user or the $mail_owner user.
       Otherwise, the real UID of the process is looked	up in the system pass-
       word file, and access is	granted	only if	the corresponding  login  name
       is  on  the  access list.  The username "unknown" is used for processes
       whose real UID is not found in the password file.

       Specify a list of user names, "/file/name"  or  "type:table"  patterns,
       separated  by  commas  and/or  whitespace.  The list is matched left to
       right, and the search stops on the first	match. A "/file/name"  pattern
       is  replaced  by	 its  contents;	a "type:table" lookup table is matched
       when a name matches a lookup key	(the lookup result is ignored).	  Con-
       tinue  long  lines  by  starting	the next line with whitespace. Specify
       "!pattern" to exclude a name from the list. The form  "!/file/name"  is
       supported only in Postfix version 2.4 and later.

       This feature is available in Postfix 2.2	and later.

authorized_mailq_users (default: static:anyone)
       List of users who are authorized	to view	the queue.

       By  default, all	users are allowed to view the queue.  Access is	always
       granted if the invoking user is the super-user or the $mail_owner user.
       Otherwise, the real UID of the process is looked	up in the system pass-
       word file, and access is	granted	only if	the corresponding  login  name
       is  on  the  access list.  The username "unknown" is used for processes
       whose real UID is not found in the password file.

       Specify a list of user names, "/file/name"  or  "type:table"  patterns,
       separated  by  commas  and/or  whitespace.  The list is matched left to
       right, and the search stops on the first	match. A "/file/name"  pattern
       is  replaced  by	 its  contents;	a "type:table" lookup table is matched
       when a name matches a lookup key	(the lookup result is ignored).	  Con-
       tinue  long  lines  by  starting	the next line with whitespace. Specify
       "!pattern" to exclude a user name from the list.	The form "!/file/name"
       is supported only in Postfix version 2.4	and later.

       This feature is available in Postfix 2.2	and later.

authorized_submit_users	(default: static:anyone)
       List  of	 users	who are	authorized to submit mail with the sendmail(1)
       command (and with the privileged	postdrop(1) helper command).

       By default, all users are allowed to submit mail.  Otherwise, the  real
       UID of the process is looked up in the system password file, and	access
       is granted only if the corresponding login name is on the access	 list.
       The  username  "unknown"	 is  used  for processes whose real UID	is not
       found in	the password file. To deny mail	submission access to all users
       specify an empty	list.

       Specify	a  list	 of user names,	"/file/name" or	"type:table" patterns,
       separated by commas and/or whitespace. The  list	 is  matched  left  to
       right,  and the search stops on the first match.	A "/file/name" pattern
       is replaced by its contents; a "type:table"  lookup  table  is  matched
       when  a name matches a lookup key (the lookup result is ignored).  Con-
       tinue long lines	by starting the	next  line  with  whitespace.  Specify
       "!pattern" to exclude a user name from the list.	The form "!/file/name"
       is supported only in Postfix version 2.4	and later.

       Example:

       authorized_submit_users = !www, static:all

       This feature is available in Postfix 2.2	and later.

authorized_verp_clients	(default: $mynetworks)
       What remote SMTP	clients	are allowed  to	 specify  the  XVERP  command.
       This  command  requests	that mail be delivered one recipient at	a time
       with a per recipient return address.

       By default, only	trusted	clients	are allowed to specify XVERP.

       This parameter was introduced with Postfix version 1.1.	 Postfix  ver-
       sion  2.1  renamed  this	parameter to smtpd_authorized_verp_clients and
       changed the default to none.

       Specify a list of network/netmask patterns, separated by	commas	and/or
       whitespace.  The	 mask specifies	the number of bits in the network part
       of a host address. You can also specify hostnames or .domain names (the
       initial	 dot   causes	the  domain  to	 match	any  name  below  it),
       "/file/name" or "type:table" patterns.  A "/file/name" pattern  is  re-
       placed  by  its contents; a "type:table"	lookup table is	matched	when a
       table entry matches a lookup string (the	 lookup	 result	 is  ignored).
       Continue	 long lines by starting	the next line with whitespace. Specify
       "!pattern" to exclude an	address	or network block from  the  list.  The
       form "!/file/name" is supported only in Postfix version 2.4 and later.

       Note:  IP  version 6 address information	must be	specified inside [] in
       the  authorized_verp_clients  value,  and  in  files   specified	  with
       "/file/name".   IP  version  6 addresses	contain	the ":"	character, and
       would otherwise be confused with	a "type:table" pattern.

backwards_bounce_logfile_compatibility (default: yes)
       Produce additional bounce(8) logfile records that can be	read by	 Post-
       fix versions before 2.0.	The current and	more extensible	"name =	value"
       format is needed	in order to implement more  sophisticated  functional-
       ity.

       This feature is available in Postfix 2.1	and later.

berkeley_db_create_buffer_size (default: 16777216)
       The per-table I/O buffer	size for programs that create Berkeley DB hash
       or btree	tables.	 Specify a byte	count.

       This feature is available in Postfix 2.0	and later.

berkeley_db_read_buffer_size (default: 131072)
       The per-table I/O buffer	size for programs that read Berkeley  DB  hash
       or btree	tables.	 Specify a byte	count.

       This feature is available in Postfix 2.0	and later.

best_mx_transport (default: empty)
       Where  the  Postfix  SMTP  client should	deliver	mail when it detects a
       "mail loops back	to myself" error condition. This happens when the  lo-
       cal MTA is the best SMTP	mail exchanger for a destination not listed in
       $mydestination, $inet_interfaces, $proxy_interfaces, $virtual_alias_do-
       mains,  or  $virtual_mailbox_domains.   By  default,  the  Postfix SMTP
       client returns such mail	as undeliverable.

       Specify,	for example, "best_mx_transport	= local" to pass the mail from
       the Postfix SMTP	client to the local(8) delivery	agent. You can specify
       any message delivery "transport"	or "transport:nexthop" that is defined
       in  the master.cf file. See the transport(5) manual page	for the	syntax
       and meaning of "transport" or "transport:nexthop".

       However,	this feature is	expensive because it ties up  a	 Postfix  SMTP
       client  process while the local(8) delivery agent is doing its work. It
       is more efficient (for Postfix) to list all hosted domains in  a	 table
       or database.

biff (default: yes)
       Whether	or not to use the local	biff service.  This service sends "new
       mail" notifications to users who	have requested new  mail  notification
       with the	UNIX command "biff y".

       For  compatibility  reasons  this feature is on by default.  On systems
       with lots of interactive	users, the biff	service	can be	a  performance
       drain.  Specify "biff = no" in main.cf to disable.

body_checks (default: empty)
       Optional	 lookup	 tables	 for  content  inspection  as specified	in the
       body_checks(5) manual page.

       Note: with Postfix versions before 2.0, these rules inspect all content
       after the primary message headers.

body_checks_size_limit (default: 51200)
       How  much  text in a message body segment (or attachment, if you	prefer
       to use that term) is subjected to body_checks inspection.   The	amount
       of text is limited to avoid scanning huge attachments.

       This feature is available in Postfix 2.0	and later.

bounce_notice_recipient	(default: postmaster)
       The  recipient  of postmaster notifications with	the message headers of
       mail that Postfix did not deliver and of	SMTP conversation  transcripts
       of mail that Postfix did	not receive.  This feature is enabled with the
       notify_classes parameter.

bounce_queue_lifetime (default:	5d)
       Consider	a bounce message as undeliverable, when	delivery fails with  a
       temporary   error,   and	  the  time  in	 the  queue  has  reached  the
       bounce_queue_lifetime limit.  By	default, this limit is the same	as for
       regular mail.

       Specify	a  non-negative	time value (an integral	value plus an optional
       one-letter suffix that specifies	the time unit).	 Time units:  s	 (sec-
       onds),  m  (minutes), h (hours),	d (days), w (weeks).  The default time
       unit is d (days).

       Specify 0 when mail delivery should be tried only once.

       This feature is available in Postfix 2.1	and later.

bounce_service_name (default: bounce)
       The name	of the bounce(8) service. This service maintains a  record  of
       failed delivery attempts	and generates non-delivery notifications.

       This feature is available in Postfix 2.0	and later.

bounce_size_limit (default: 50000)
       The  maximal  amount of original	message	text that is sent in a non-de-
       livery notification. Specify a byte count.  A message  is  returned  as
       either message/rfc822 (the complete original) or	as text/rfc822-headers
       (the headers only).  With Postfix version 2.4 and earlier, a message is
       always  returned	as message/rfc822 and is truncated when	it exceeds the
       size limit.

       Notes:

       o      If you  increase	this  limit,  then  you	 should	 increase  the
	      mime_nesting_limit value proportionally.

       o      Be  careful  when	making changes.	 Excessively large values will
	      result in	the loss of non-delivery notifications,	when a	bounce
	      message size exceeds a local or remote MTA's message size	limit.

bounce_template_file (default: empty)
       Pathname	 of a configuration file with bounce message templates.	 These
       override	the built-in templates of delivery status  notification	 (DSN)
       messages	 for undeliverable mail, delayed mail, successful delivery, or
       delivery	verification. The bounce(5) manual page	describes how to  edit
       and test	template files.

       Template	message	body text may contain $name references to Postfix con-
       figuration parameters. The result of $name expansion can	 be  previewed
       with "postconf -b file_name" before the file is placed into the Postfix
       configuration directory.

       This feature is available in Postfix 2.3	and later.

broken_sasl_auth_clients (default: no)
       Enable interoperability with remote SMTP	clients	that implement an  ob-
       solete version of the AUTH command (RFC 4954). Examples of such clients
       are MicroSoft Outlook Express version 4 and MicroSoft Exchange  version
       5.0.

       Specify "broken_sasl_auth_clients = yes"	to have	Postfix	advertise AUTH
       support in a non-standard way.

canonical_classes     (default:	     envelope_sender,	   envelope_recipient,
       header_sender, header_recipient)
       What  addresses	are subject to canonical_maps address mapping.	By de-
       fault, canonical_maps address mapping is	applied	to envelope sender and
       recipient  addresses,  and  to  header  sender and header recipient ad-
       dresses.

       Specify	one   or   more	  of:	envelope_sender,   envelope_recipient,
       header_sender, header_recipient

       This feature is available in Postfix 2.2	and later.

canonical_maps (default: empty)
       Optional	 address  mapping  lookup  tables  for message headers and en-
       velopes.	The mapping is applied to both sender and recipient addresses,
       in  both	 envelopes  and	 in  headers,  as  controlled with the canoni-
       cal_classes parameter. This is typically	used to	 clean	up  dirty  ad-
       dresses	from  legacy mail systems, or to replace login names by	First-
       name.Lastname.  The table format	and lookups are	documented in  canoni-
       cal(5).	For  an	 overview of Postfix address manipulations see the AD-
       DRESS_REWRITING_README document.

       Specify zero or more "type:name"	lookup tables, separated by whitespace
       or  comma. Tables will be searched in the specified order until a match
       is found.  Note:	these lookups are recursive.

       If you use this feature,	run "postmap /usr/local/etc/postfix/canonical"
       to  build  the necessary	DBM or DB file after every change. The changes
       will become visible after a minute or  so.   Use	 "postfix  reload"  to
       eliminate the delay.

       Note:  with Postfix version 2.2,	message	header address mapping happens
       only when message header	address	rewriting is enabled:

       o      The message is received with the Postfix sendmail(1) command,

       o      The message is received from a network client that matches  $lo-
	      cal_header_rewrite_clients,

       o      The   message   is  received  from  the  network,	 and  the  re-
	      mote_header_rewrite_domain  parameter  specifies	 a   non-empty
	      value.

       To   get	  the  behavior	 before	 Postfix  version  2.2,	 specify  "lo-
       cal_header_rewrite_clients = static:all".

       Examples:

       canonical_maps =	dbm:$config_directory/canonical
       canonical_maps =	hash:$config_directory/canonical

cleanup_service_name (default: cleanup)
       The name	of the cleanup(8) service.  This  service  rewrites  addresses
       into  the  standard form, and performs canonical(5) address mapping and
       virtual(5) aliasing.

       This feature is available in Postfix 2.0	and later.

command_directory (default: see	postconf -d output)
       The location of all postfix administrative commands.

command_execution_directory (default: empty)
       The local(8) delivery agent working directory for delivery to  external
       commands.   Failure  to	change directory causes	the delivery to	be de-
       ferred.

       The command_execution_directory value is	not subject to Postfix config-
       uration	parameter $name	expansion. Instead, the	following $name	expan-
       sions are done on command_execution_directory before the	 directory  is
       used.  Expansion	 happens  in the context of the	delivery request.  The
       result of $name expansion is filtered with the character	 set  that  is
       specified with the execution_directory_expansion_filter parameter.

       $user  The recipient's username.

       $shell The recipient's login shell pathname.

       $home  The recipient's home directory.

       $recipient
	      The full recipient address.

       $extension
	      The optional recipient address extension.

       $domain
	      The recipient domain.

       $local The entire recipient localpart.

       $recipient_delimiter
	      The  address extension delimiter that was	found in the recipient
	      address (Postfix 2.11 and	later),	or the	system-wide  recipient
	      address extension	delimiter (Postfix 2.10	and earlier).

       ${name?value}

       ${name?{value}} (Postfix	>= 3.0)
	      Expands to value when $name is non-empty.

       ${name:value}

       ${name:{value}} (Postfix	>= 3.0)
	      Expands to value when $name is empty.

       ${name?{value1}:{value2}} (Postfix >= 3.0)
	      Expands to value1	when $name is non-empty, value2	otherwise.

       Instead of $name	you can	also specify ${name} or	$(name).

       This feature is available in Postfix 2.2	and later.

command_expansion_filter (default: see postconf	-d output)
       Restrict	 the  characters  that	the  local(8) delivery agent allows in
       $name expansions	of $mailbox_command and	 $command_execution_directory.
       Characters outside the allowed set are replaced by underscores.

command_time_limit (default: 1000s)
       Time limit for delivery to external commands. This limit	is used	by the
       local(8)	delivery agent,	and is the default time	limit for delivery  by
       the pipe(8) delivery agent.

       Note:  if  you set this time limit to a large value you must update the
       global ipc_timeout parameter as well.

compatibility_level (default: 0)
       A safety	net that causes	Postfix	to run with  backwards-compatible  de-
       fault settings after an upgrade to a newer Postfix version.

       With backwards compatibility turned on (the main.cf compatibility_level
       value is	less than the Postfix built-in value), Postfix looks for  set-
       tings that are left at their implicit default value, and	logs a message
       when a backwards-compatible default setting is required.

	   using backwards-compatible default setting name=value
	       to [accept a specific client request]

	   using backwards-compatible default setting name=value
	       to [enable specific Postfix behavior]

       See COMPATIBILITY_README	for specific message details. If such  a  mes-
       sage  is	 logged	in the context of a legitimate request,	the system ad-
       ministrator should make the backwards-compatible	setting	 permanent  in
       main.cf or master.cf, for example:

	   # postconf name=value
	   # postfix reload

       When  no	 more backwards-compatible settings need to be made permanent,
       the administrator should	turn off backwards compatibility  by  updating
       the compatibility_level setting in main.cf:

	   # postconf compatibility_level=N
	   # postfix reload

       For N specify the number	that is	logged in your postfix(1) warning mes-
       sage:

	   warning: To disable backwards compatibility use "postconf
	       compatibility_level=N" and "postfix reload"

       Starting	with Postfix version 3.6, the compatibility level in the above
       warning	message	is the Postfix version that introduced the last	incom-
       patible change. The level  is  formatted	 as  major.minor.patch,	 where
       patch  is  usually  omitted and defaults	to zero. Earlier compatibility
       levels are 0, 1 and 2.

       NOTE: this also introduces support for  the  "<level",  "<=level",  and
       other operators to compare compatibility	levels.	 With the standard op-
       erators "<", "<=", etc.,	compatibility level "3.10"  would  be  smaller
       than "3.9" which	is undesirable.

       This feature is available in Postfix 3.0	and later.

config_directory (default: see postconf	-d output)
       The default location of the Postfix main.cf and master.cf configuration
       files. This can be overruled via	the following mechanisms:

       o      The MAIL_CONFIG environment variable (daemon processes and  com-
	      mands).

       o      The "-c" command-line option (commands only).

       With Postfix commands that run with set-gid privileges, a config_direc-
       tory override either requires root privileges, or it requires that  the
       directory  is listed with the alternate_config_directories parameter in
       the default main.cf file.

confirm_delay_cleared (default:	no)
       After sending a "your message  is  delayed"  notification,  inform  the
       sender  when  the delay clears up. This can result in a sudden burst of
       notifications at	the end	of a prolonged network outage, and  is	there-
       fore disabled by	default.

       See also: delay_warning_time.

       This feature is available in Postfix 3.0	and later.

connection_cache_protocol_timeout (default: 5s)
       Time  limit  for	 connection cache connect, send	or receive operations.
       The time	limit is enforced in the client.

       This feature is available in Postfix 2.3	and later.

connection_cache_service_name (default:	scache)
       The name	of the scache(8) connection cache service.  This service main-
       tains a limited pool of cached sessions.

       This feature is available in Postfix 2.2	and later.

connection_cache_status_update_time (default: 600s)
       How  frequently the scache(8) server logs usage statistics with connec-
       tion cache hit and miss rates for logical destinations and for physical
       endpoints.

connection_cache_ttl_limit (default: 2s)
       The  maximal  time-to-live  value  that	the scache(8) connection cache
       server allows. Requests that specify a larger TTL will be  stored  with
       the  maximum  allowed TTL. The purpose of this additional control is to
       protect the infrastructure against careless people. The	cache  TTL  is
       already bounded by $max_idle.

content_filter (default: empty)
       After  the  message is queued, send the entire message to the specified
       transport:destination. The transport name specifies the first field  of
       a  mail	delivery  agent	 definition  in	 master.cf;  the syntax	of the
       next-hop	destination is described in the	manual page of the correspond-
       ing delivery agent.  More information about external content filters is
       in the Postfix FILTER_README file.

       Notes:

       o      This setting has lower precedence	than a FILTER action  that  is
	      specified	 in  an	 access(5), header_checks(5) or	body_checks(5)
	      table.

       o      The meaning of an	empty next-hop filter destination  is  version
	      dependent.  Postfix 2.7 and later	will use the recipient domain;
	      earlier versions will use	 $myhostname.	Specify	 "default_fil-
	      ter_nexthop = $myhostname" for compatibility with	Postfix	2.6 or
	      earlier, or specify a  content_filter  value  with  an  explicit
	      next-hop destination.

cyrus_sasl_config_path (default: empty)
       Search  path  for Cyrus SASL application	configuration files, currently
       used only to locate the $smtpd_sasl_path.conf file.   Specify  zero  or
       more  directories  separated by a colon character, or an	empty value to
       use Cyrus SASL's	built-in search	path.

       This feature is available in Postfix 2.5	and later when	compiled  with
       Cyrus SASL 2.1.22 or later.

daemon_directory (default: see postconf	-d output)
       The directory with Postfix support programs and daemon programs.	 These
       should not be invoked directly by humans. The directory must  be	 owned
       by root.

daemon_table_open_error_is_fatal (default: no)
       How  a  Postfix	daemon process handles errors while opening lookup ta-
       bles: gradual degradation or immediate termination.

	no  (default)
	      Gradual degradation: a daemon process logs  a  message  of  type
	      "error" and continues execution with reduced functionality. Fea-
	      tures that do not	depend on the unavailable table	will work nor-
	      mally,  while features that depend on the	table will result in a
	      type "warning" message.
	      When the notify_classes  parameter  value	 contains  the	"data"
	      class,  the  Postfix  SMTP  server  and client will report tran-
	      scripts of sessions with an error	because	a  table  is  unavail-
	      able.

	yes  (historical behavior)
	      Immediate	termination: a daemon process logs a type "fatal" mes-
	      sage and terminates immediately.	This option reduces the	number
	      of  possible  code  paths	 through Postfix, and may therefore be
	      slightly more secure than	the default.

       For the sake of sanity, the number of type "error" messages is  limited
       to 13 over the lifetime of a daemon process.

       This feature is available in Postfix 2.9	and later.

daemon_timeout (default: 18000s)
       How much	time a Postfix daemon process may take to handle a request be-
       fore it is terminated by	a built-in watchdog timer.

       Specify a non-zero time value  (an  integral  value  plus  an  optional
       one-letter  suffix  that	specifies the time unit).  Time	units: s (sec-
       onds), m	(minutes), h (hours), d	(days),	w (weeks).  The	 default  time
       unit is s (seconds).

data_directory (default: see postconf -d output)
       The  directory  with  Postfix-writable data files (for example: caches,
       pseudo-random numbers).	This directory must be owned by	the mail_owner
       account,	and must not be	shared with non-Postfix	software.

       This feature is available in Postfix 2.5	and later.

debug_peer_level (default: 2)
       The  increment in verbose logging level when a nexthop destination, re-
       mote client or server name or network address matches a	pattern	 given
       with the	debug_peer_list	parameter.

       Per-nexthop debug logging is available in Postfix 3.6 and later.

debug_peer_list	(default: empty)
       Optional	 list  of nexthop destination, remote client or	server name or
       network address patterns	that, if matched, cause	 the  verbose  logging
       level to	increase by the	amount specified in $debug_peer_level.

       Per-nexthop debug logging is available in Postfix 3.6 and later.

       Specify	domain	names, network/netmask patterns, "/file/name" patterns
       or  "type:table"	 lookup	 tables.  The  right-hand  side	 result	  from
       "type:table" lookups is ignored.

       Pattern	matching  of domain names is controlled	by the presence	or ab-
       sence of	"debug_peer_list" in the parent_domain_matches_subdomains  pa-
       rameter value.

       Examples:

       debug_peer_list = 127.0.0.1
       debug_peer_list = example.com

debugger_command (default: empty)
       The  external  command  to execute when a Postfix daemon	program	is in-
       voked with the -D option.

       Use "command .. & sleep 5" so that the debugger can attach  before  the
       process	marches	 on. If	you use	an X-based debugger, be	sure to	set up
       your XAUTHORITY environment variable before starting Postfix.

       Note: the command is subject to $name expansion,	before it is passed to
       the  default  command interpreter. Specify "$$" to produce a single "$"
       character.

       Example:

       debugger_command	=
	   PATH=/usr/bin:/usr/X11R6/bin
	   ddd $daemon_directory/$process_name $process_id & sleep 5

default_database_type (default:	see postconf -d	output)
       The default database type for use in  newaliases(1),  postalias(1)  and
       postmap(1)  commands.  On  many UNIX systems the	default	type is	either
       dbm or hash. The	default	setting	is frozen when the Postfix  system  is
       built.

       Examples:

       default_database_type = hash
       default_database_type = dbm

default_delivery_slot_cost (default: 5)
       How  often  the Postfix queue manager's scheduler is allowed to preempt
       delivery	of one message with another.

       Each transport maintains	a so-called "available delivery	slot  counter"
       for  each message. One message can be preempted by another one when the
       other message can be delivered using no more delivery slots (i.e.,  in-
       vocations  of delivery agents) than the current message counter has ac-
       cumulated (or will eventually accumulate	- see about slot loans below).
       This  parameter controls	how often the counter is incremented - it hap-
       pens after each default_delivery_slot_cost recipients have been	deliv-
       ered.

       The  cost of 0 is used to disable the preempting	scheduling completely.
       The minimum value the scheduling	algorithm can use is 2 - use it	if you
       want to maximize	the message throughput rate. Although there is no max-
       imum, it	doesn't	make much sense	to use values above say	50.

       The only	reason why the value of	2 is not the default is	the  way  this
       parameter affects the delivery of mailing-list mail. In the worst case,
       delivery	can take somewhere  between  (cost+1/cost)  and	 (cost/cost-1)
       times  more  than if the	preemptive scheduler was disabled. The default
       value of	5 turns	out to provide reasonable message response times while
       making  sure  the mailing-list deliveries are not extended by more than
       20-25 percent even in the worst case.

       Use transport_delivery_slot_cost	to specify a transport-specific	 over-
       ride,  where  transport	is  the	master.cf name of the message delivery
       transport.

       Examples:

       default_delivery_slot_cost = 0
       default_delivery_slot_cost = 2

default_delivery_slot_discount (default: 50)
       The default value for transport-specific	 _delivery_slot_discount  set-
       tings.

       This  parameter speeds up the moment when a message preemption can hap-
       pen. Instead of waiting until the full amount  of  delivery  slots  re-
       quired  is  available,  the preemption can happen when transport_deliv-
       ery_slot_discount percent of the	required amount	plus  transport_deliv-
       ery_slot_loan  still  remains  to  be  accumulated.  Note that the full
       amount will still have to be accumulated	before another preemption  can
       take place later.

       Use  transport_delivery_slot_discount  to  specify a transport-specific
       override, where transport is the	master.cf name of the message delivery
       transport.

default_delivery_slot_loan (default: 3)
       The default value for transport-specific	_delivery_slot_loan settings.

       This  parameter speeds up the moment when a message preemption can hap-
       pen. Instead of waiting until the full amount  of  delivery  slots  re-
       quired  is  available,  the preemption can happen when transport_deliv-
       ery_slot_discount percent of the	required amount	plus  transport_deliv-
       ery_slot_loan  still  remains  to  be  accumulated.  Note that the full
       amount will still have to be accumulated	before another preemption  can
       take place later.

       Use  transport_delivery_slot_loan to specify a transport-specific over-
       ride, where transport is	the master.cf name  of	the  message  delivery
       transport.

default_delivery_status_filter (default: empty)
       Optional	filter to replace the delivery status code or explanatory text
       of successful or	unsuccessful deliveries.  This does not	allow the  re-
       placement of a successful status	code (2.X.X) with an unsuccessful sta-
       tus code	(4.X.X or 5.X.X) or vice versa.

       Note: the (smtp|lmtp)_delivery_status_filter is applied only  once  per
       recipient:  when	delivery is successful,	when delivery is rejected with
       5XX, or when there are no more alternate	 MX  or	 A  destinations.  Use
       smtp_reply_filter or lmtp_reply_filter to inspect responses for all de-
       livery attempts.

       The following parameters	can be used to implement a filter for specific
       delivery	  agents:   lmtp_delivery_status_filter,   local_delivery_sta-
       tus_filter, pipe_delivery_status_filter,	smtp_delivery_status_filter or
       virtual_delivery_status_filter.	These parameters support the same fil-
       ter syntax as described here.

       Specify zero or more "type:table"  lookup  table	 names,	 separated  by
       comma  or whitespace. For each successful or unsuccessful delivery to a
       recipient, the tables are queried in the	specified order	with one  line
       of text that is structured as follows:

	   enhanced-status-code	SPACE explanatory-text

       The first table match wins. The lookup result must have the same	struc-
       ture as the query, a successful status code (2.X.X)  must  be  replaced
       with  a	successful  status code, an unsuccessful status	code (4.X.X or
       5.X.X) must be replaced with an unsuccessful status code, and  the  ex-
       planatory  text field must be non-empty.	Other results will result in a
       warning.

       Example 1: convert specific soft	TLS errors into	hard errors, by	 over-
       riding the first	number in the enhanced status code.

	   /usr/local/etc/postfix/main.cf:
	       smtp_delivery_status_filter = pcre:$config_directory/smtp_dsn_filter

	   /usr/local/etc/postfix/smtp_dsn_filter:
	       /^4(\.\d+\.\d+ TLS is required, but host	\S+ refused to start TLS: .+)/
		   5$1
	       /^4(\.\d+\.\d+ TLS is required, but was not offered by host .+)/
		   5$1
	       # Do not	change the following into hard bounces.	They may
	       # result	from a local configuration problem.
	       # 4.\d+.\d+ TLS is required, but	our TLS	engine is unavailable
	       # 4.\d+.\d+ TLS is required, but	unavailable
	       # 4.\d+.\d+ Cannot start	TLS: handshake failure

       Example	2:  censor  the	 per-recipient delivery	status text so that it
       does not	reveal the destination	command	 or  filename  when  a	remote
       sender requests confirmation of successful delivery.

	   /usr/local/etc/postfix/main.cf:
	       local_delivery_status_filter = pcre:$config_directory/local_dsn_filter

	   /usr/local/etc/postfix/local_dsn_filter:
	       /^(2\S+ delivered to file).+/	$1
	       /^(2\S+ delivered to command).+/	$1

       Notes:

       o      This feature will	NOT override the soft_bounce safety net.

       o      This  feature will change	the enhanced status code and text that
	      is logged	to the maillog file,  and  that	 is  reported  to  the
	      sender in	delivery confirmation or non-delivery notifications.

       This feature is available in Postfix 3.0	and later.

default_destination_concurrency_failed_cohort_limit (default: 1)
       How many	pseudo-cohorts must suffer connection or handshake failure be-
       fore a specific destination is considered unavailable (and further  de-
       livery  is suspended). Specify zero to disable this feature. A destina-
       tion's pseudo-cohort failure count is reset each	time a	delivery  com-
       pletes without connection or handshake failure for that specific	desti-
       nation.

       A pseudo-cohort is the number of	deliveries equal  to  a	 destination's
       delivery	concurrency.

       Use  transport_destination_concurrency_failed_cohort_limit to specify a
       transport-specific override, where transport is the master.cf  name  of
       the message delivery transport.

       This  feature  is available in Postfix 2.5. The default setting is com-
       patible with earlier Postfix versions.

default_destination_concurrency_limit (default:	20)
       The default maximal number of parallel deliveries to the	same  destina-
       tion.  This is the default limit	for delivery via the lmtp(8), pipe(8),
       smtp(8) and virtual(8) delivery agents.	With a per-destination recipi-
       ent limit > 1, a	destination is a domain, otherwise it is a recipient.

       Use transport_destination_concurrency_limit to specify a	transport-spe-
       cific override, where transport is the master.cf	name  of  the  message
       delivery	transport.

default_destination_concurrency_negative_feedback (default: 1)
       The  per-destination  amount of delivery	concurrency negative feedback,
       after a delivery	completes with	a  connection  or  handshake  failure.
       Feedback	 values	 are  in the range 0..1	inclusive. With	negative feed-
       back, concurrency is decremented	at the	beginning  of  a  sequence  of
       length  1/feedback. This	is unlike positive feedback, where concurrency
       is incremented at the end of a sequence of length 1/feedback.

       As of Postfix version 2.5, negative  feedback  cannot  reduce  delivery
       concurrency  to	zero.	Instead, a destination is marked dead (further
       delivery	suspended) after the failed pseudo-cohort count	 reaches  $de-
       fault_destination_concurrency_failed_cohort_limit (or $transport_desti-
       nation_concurrency_failed_cohort_limit).	 To make  the  scheduler  com-
       pletely	immune	to  connection	or  handshake failures,	specify	a zero
       feedback	value and a zero failed	pseudo-cohort limit.

       Specify one of the following forms:

       number

       number /	number
	      Constant feedback. The value must	be in the  range  0..1	inclu-
	      sive.   The  default  setting  of	"1" is compatible with Postfix
	      versions before 2.5, where a destination's delivery  concurrency
	      is throttled down	to zero	(and further delivery suspended) after
	      a	single failed pseudo-cohort.

       number /	concurrency
	      Variable feedback	of "number  /  (delivery  concurrency)".   The
	      number must be in	the range 0..1 inclusive. With number equal to
	      "1", a destination's delivery concurrency	is  decremented	 by  1
	      after each failed	pseudo-cohort.

       A  pseudo-cohort	 is  the number	of deliveries equal to a destination's
       delivery	concurrency.

       Use transport_destination_concurrency_negative_feedback	to  specify  a
       transport-specific  override,  where transport is the master.cf name of
       the message delivery transport.

       This feature is available in Postfix 2.5. The default setting  is  com-
       patible with earlier Postfix versions.

default_destination_concurrency_positive_feedback (default: 1)
       The  per-destination  amount of delivery	concurrency positive feedback,
       after a delivery	completes without  connection  or  handshake  failure.
       Feedback	 values	 are in	the range 0..1 inclusive.  The concurrency in-
       creases until it	reaches	the per-destination maximal concurrency	limit.
       With  positive feedback,	concurrency is incremented at the end of a se-
       quence with length 1/feedback. This is unlike negative feedback,	 where
       concurrency is decremented at the start of a sequence of	length 1/feed-
       back.

       Specify one of the following forms:

       number

       number /	number
	      Constant feedback.  The value must be in the range  0..1	inclu-
	      sive. The	default	setting	of "1" is compatible with Postfix ver-
	      sions before 2.5,	where  a  destination's	 delivery  concurrency
	      doubles after each successful pseudo-cohort.

       number /	concurrency
	      Variable	feedback  of  "number  / (delivery concurrency)".  The
	      number must be in	the range 0..1 inclusive. With number equal to
	      "1",  a  destination's  delivery concurrency is incremented by 1
	      after each successful pseudo-cohort.

       A pseudo-cohort is the number of	deliveries equal  to  a	 destination's
       delivery	concurrency.

       Use  transport_destination_concurrency_positive_feedback	 to  specify a
       transport-specific override, where transport is the master.cf  name  of
       the message delivery transport.

       This feature is available in Postfix 2.5	and later.

default_destination_rate_delay (default: 0s)
       The default amount of delay that	is inserted between individual message
       deliveries to the same destination and over the same  message  delivery
       transport.  Specify a non-zero value to rate-limit those	message	deliv-
       eries to	at most	one per	$default_destination_rate_delay.

       The resulting behavior  depends	on  the	 value	of  the	 corresponding
       per-destination recipient limit.

       o      With  a  corresponding  per-destination recipient	limit >	1, the
	      rate delay specifies the time between deliveries to the same do-
	      main.   Different	 domains are delivered in parallel, subject to
	      the process limits specified in master.cf.

       o      With a corresponding per-destination recipient limit equal to 1,
	      the rate delay specifies the time	between	deliveries to the same
	      recipient. Different recipients are delivered in parallel,  sub-
	      ject to the process limits specified in master.cf.

       To  enable  the delay, specify a	non-zero time value (an	integral value
       plus an optional	one-letter suffix that specifies the time unit).

       Time units: s (seconds),	m (minutes), h (hours),	d (days),  w  (weeks).
       The default time	unit is	s (seconds).

       NOTE: the delay is enforced by the queue	manager. The delay timer state
       does not	survive	"postfix reload" or "postfix stop".

       Use transport_destination_rate_delay to	specify	 a  transport-specific
       override, where transport is the	master.cf name of the message delivery
       transport.

       NOTE: with a non-zero _destination_rate_delay, specify a	transport_des-
       tination_concurrency_failed_cohort_limit	of 10 or more to prevent Post-
       fix from	deferring all mail for the same	 destination  after  only  one
       connection or handshake error.

       This feature is available in Postfix 2.5	and later.

default_destination_recipient_limit (default: 50)
       The default maximal number of recipients	per message delivery.  This is
       the default limit for delivery via the lmtp(8),	pipe(8),  smtp(8)  and
       virtual(8) delivery agents.

       Setting this parameter to a value of 1 affects email deliveries as fol-
       lows:

       o      It changes the meaning of	the corresponding per-destination con-
	      currency	limit,	from concurrency of deliveries to the same do-
	      main into	concurrency of deliveries to the same recipient.  Dif-
	      ferent  recipients  are  delivered  in  parallel,	subject	to the
	      process limits specified in master.cf.

       o      It changes the meaning of	the corresponding per-destination rate
	      delay, from the delay between deliveries to the same domain into
	      the delay	between	deliveries to the same recipient.  Again, dif-
	      ferent  recipients  are  delivered  in  parallel,	subject	to the
	      process limits specified in master.cf.

       o      It changes the meaning of	 other	corresponding  per-destination
	      settings	in a similar manner, from settings for delivery	to the
	      same domain into settings	for delivery to	the same recipient.

       Use transport_destination_recipient_limit to specify  a	transport-spe-
       cific  override,	 where	transport is the master.cf name	of the message
       delivery	transport.

default_extra_recipient_limit (default:	1000)
       The default value for the extra per-transport limit imposed on the num-
       ber  of	in-memory  recipients.	This extra recipient space is reserved
       for the cases when the Postfix queue manager's scheduler	 preempts  one
       message	with another and suddenly needs	some extra recipient slots for
       the chosen message in order to avoid performance	degradation.

       Use transport_extra_recipient_limit  to	specify	 a  transport-specific
       override, where transport is the	master.cf name of the message delivery
       transport.

default_filter_nexthop (default: empty)
       When a content_filter or	FILTER request specifies no explicit  next-hop
       destination,  use  $default_filter_nexthop  instead; when that value is
       empty, use the domain in	the recipient address.	Specify	 "default_fil-
       ter_nexthop  =  $myhostname" for	compatibility with Postfix version 2.6
       and earlier, or specify an explicit next-hop destination	with each con-
       tent_filter value or FILTER action.

       This feature is available in Postfix 2.7	and later.

default_minimum_delivery_slots (default: 3)
       How  many recipients a message must have	in order to invoke the Postfix
       queue manager's scheduling algorithm  at	 all.	Messages  which	 would
       never  accumulate  at  least  this many delivery	slots (subject to slot
       cost parameter as well) are never preempted.

       Use transport_minimum_delivery_slots to	specify	 a  transport-specific
       override, where transport is the	master.cf name of the message delivery
       transport.

default_privs (default:	nobody)
       The default rights used by the local(8) delivery	agent for delivery  to
       an  external  file  or command.	These rights are used when delivery is
       requested from an aliases(5) file that is owned by root,	or when	deliv-
       ery  is done on behalf of root. DO NOT SPECIFY A	PRIVILEGED USER	OR THE
       POSTFIX OWNER.

default_process_limit (default:	100)
       The default maximal number of Postfix child processes  that  provide  a
       given service. This limit can be	overruled for specific services	in the
       master.cf file.

default_rbl_reply (default: see	postconf -d output)
       The default Postfix SMTP	server response	template for a request that is
       rejected	by an RBL-based	restriction. This template can be overruled by
       specific	entries	in the optional	rbl_reply_maps lookup table.

       This feature is available in Postfix 2.0	and later.

       The template does not support  Postfix  configuration  parameter	 $name
       substitution. Instead, it supports exactly one level of $name substitu-
       tion for	the following attributes:

       $client
	      The client hostname and IP address, formatted as name[address].

       $client_address
	      The client IP address.

       $client_name
	      The   client   hostname	 or    "unknown".    See    reject_un-
	      known_client_hostname for	more details.

       $reverse_client_name
	      The  client  hostname  from  address->name lookup, or "unknown".
	      See reject_unknown_reverse_client_hostname for more details.

       $helo_name
	      The hostname given in HELO or EHLO command or empty string.

       $rbl_class
	      The denylisted entity type: Client host,	Helo  command,	Sender
	      address, or Recipient address.

       $rbl_code
	      The   numerical  SMTP  response  code,  as  specified  with  the
	      maps_rbl_reject_code configuration parameter. Note: The  numeri-
	      cal SMTP response	code is	required, and must appear at the start
	      of the reply. With Postfix version 2.3 and later	this  informa-
	      tion may be followed by an RFC 3463 enhanced status code.

       $rbl_domain
	      The RBL domain where $rbl_what is	denylisted.

       $rbl_reason
	      The reason why $rbl_what is denylisted, or an empty string.

       $rbl_what
	      The  entity that is denylisted (an IP address, a hostname, a do-
	      main name, or an email address whose domain was denylisted).

       $recipient
	      The recipient address or <> in case of the null address.

       $recipient_domain
	      The recipient domain or empty string.

       $recipient_name
	      The recipient address localpart or <> in case of null address.

       $sender
	      The sender address or <> in case of the null address.

       $sender_domain
	      The sender domain	or empty string.

       $sender_name
	      The sender address localpart or <> in case of the	null address.

       ${name?value}

       ${name?{value}} (Postfix	>= 3.0)
	      Expands to value when $name is non-empty.

       ${name:value}

       ${name:{value}} (Postfix	>= 3.0)
	      Expands to value when $name is empty.

       ${name?{value1}:{value2}} (Postfix >= 3.0)
	      Expands to value1	when $name is non-empty, value2	otherwise.

       Instead of $name	you can	also specify ${name} or	$(name).

       Note: when an enhanced status code is specified in an  RBL  reply  tem-
       plate,  it  is  subject to modification.	 The following transformations
       are needed when the same	RBL reply template is used for	client,	 helo,
       sender, or recipient access restrictions.

       o      When  rejecting  a  sender address, the Postfix SMTP server will
	      transform	a recipient DSN	status (e.g.,  4.1.1-4.1.6)  into  the
	      corresponding sender DSN status, and vice	versa.

       o      When rejecting non-address information (such as the HELO command
	      argument or  the	client	hostname/address),  the	 Postfix  SMTP
	      server  will  transform  a sender	or recipient DSN status	into a
	      generic non-address DSN status (e.g., 4.0.0).

default_recipient_limit	(default: 20000)
       The default per-transport upper limit on	the number of in-memory	recip-
       ients.  These limits take priority over the global qmgr_message_recipi-
       ent_limit after the message has been assigned to	the respective	trans-
       ports.  See also	default_extra_recipient_limit and qmgr_message_recipi-
       ent_minimum.

       Use transport_recipient_limit to	specify	a transport-specific override,
       where  transport	 is  the master.cf name	of the message delivery	trans-
       port.

default_recipient_refill_delay (default: 5s)
       The default per-transport maximum delay between	refilling  recipients.
       When  not  all message recipients fit into memory at once, keep loading
       more of them at least once every	this many seconds.  This  is  used  to
       make sure the recipients	are refilled in	a timely manner	even when $de-
       fault_recipient_refill_limit is too high	for too	slow deliveries.

       Use transport_recipient_refill_delay to	specify	 a  transport-specific
       override, where transport is the	master.cf name of the message delivery
       transport.

       This feature is available in Postfix 2.4	and later.

default_recipient_refill_limit (default: 100)
       The default per-transport limit on the number of	recipients refilled at
       once.   When  not  all message recipients fit into memory at once, keep
       loading more of them in batches of at least this	many at	a  time.   See
       also  $default_recipient_refill_delay,  which  may  result in recipient
       batches lower than this when this limit is too high for too slow	deliv-
       eries.

       Use  transport_recipient_refill_limit  to  specify a transport-specific
       override, where transport is the	master.cf name of the message delivery
       transport.

       This feature is available in Postfix 2.4	and later.

default_transport (default: smtp)
       The default mail	delivery transport and next-hop	destination for	desti-
       nations that do not match $mydestination, $inet_interfaces,  $proxy_in-
       terfaces,  $virtual_alias_domains,  $virtual_mailbox_domains,  or  $re-
       lay_domains.  This information can be overruled with the	 sender_depen-
       dent_default_transport_maps parameter and with the transport(5) table.

       In  order  of  decreasing  precedence, the nexthop destination is taken
       from   $sender_dependent_default_transport_maps,	   $default_transport,
       $sender_dependent_relayhost_maps, $relayhost, or	from the recipient do-
       main.

       Specify a string	of the form transport:nexthop, where transport is  the
       name  of	 a mail	delivery transport defined in master.cf.  The :nexthop
       destination is optional;	its syntax is documented in the	manual page of
       the  corresponding delivery agent. In the case of SMTP or LMTP, specify
       one or more destinations	separated by comma or whitespace (with Postfix
       3.5 and later).

       Example:

       default_transport = uucp:relayhostname

default_transport_rate_delay (default: 0s)
       The default amount of delay that	is inserted between individual message
       deliveries over the same	message	delivery transport, regardless of des-
       tination. Specify a non-zero value to rate-limit	those message deliver-
       ies to at most one per $default_transport_rate_delay.

       Use  transport_transport_rate_delay  to	specify	 a  transport-specific
       override, where the initial transport is	the master.cf name of the mes-
       sage delivery transport.

       Example:	throttle outbound SMTP	mail  to  at  most  3  deliveries  per
       minute.

       /usr/local/etc/postfix/main.cf:
	   smtp_transport_rate_delay = 20s

       To  enable  the delay, specify a	non-zero time value (an	integral value
       plus an optional	one-letter suffix that specifies the time unit).

       Time units: s (seconds),	m (minutes), h (hours),	d (days),  w  (weeks).
       The default time	unit is	s (seconds).

       NOTE: the delay is enforced by the queue	manager.

       This feature is available in Postfix 3.1	and later.

default_verp_delimiters	(default: +=)
       The  two	 default VERP delimiter	characters. These are used when	no ex-
       plicit delimiters are specified with the	SMTP XVERP command or with the
       "sendmail -XV" command-line option (Postfix 2.2 and earlier: -V). Spec-
       ify characters that are allowed by the verp_delimiter_filter setting.

       This feature is available in Postfix 1.1	and later.

defer_code (default: 450)
       The numerical Postfix SMTP server response  code	 when  a  remote  SMTP
       client request is rejected by the "defer" restriction.

       Do  not	change	this  unless  you have a complete understanding	of RFC
       5321.

defer_service_name (default: defer)
       The name	of the defer service.  This  service  is  implemented  by  the
       bounce(8) daemon	and maintains a	record of failed delivery attempts and
       generates non-delivery notifications.

       This feature is available in Postfix 2.0	and later.

defer_transports (default: empty)
       The names of message delivery transports	that should not	 deliver  mail
       unless someone issues "sendmail -q" or equivalent. Specify zero or more
       mail delivery transport names that appear in the	first  field  of  mas-
       ter.cf.

       Example:

       defer_transports	= smtp

delay_logging_resolution_limit (default: 2)
       The  maximal  number  of	 digits	 after	the decimal point when logging
       sub-second delay	values.	 Specify a number in the range 0..6.

       Large delay values are rounded off to an	integral  number  of  seconds;
       delay  values  below  the  delay_logging_resolution_limit are logged as
       "0", and	delay values under 100s	are logged with	at most	two-digit pre-
       cision.

       The format of the "delays=a/b/c/d" logging is as	follows:

       o      a	= time from message arrival to last active queue entry

       o      b	= time from last active	queue entry to connection setup

       o      c	= time in connection setup, including DNS, EHLO	and STARTTLS

       o      d	= time in message transmission

       This feature is available in Postfix 2.3	and later.

delay_notice_recipient (default: postmaster)
       The  recipient  of postmaster notifications with	the message headers of
       mail that cannot	be delivered within $delay_warning_time	time units.

       See also: delay_warning_time, notify_classes.

delay_warning_time (default: 0h)
       The time	after which the	sender receives	a copy of the message  headers
       of  mail	that is	still queued. The confirm_delay_cleared	parameter con-
       trols sender notification when the delay	clears up.

       To enable this feature, specify a  non-zero  time  value	 (an  integral
       value plus an optional one-letter suffix	that specifies the time	unit).

       Time  units:  s (seconds), m (minutes), h (hours), d (days), w (weeks).
       The default time	unit is	h (hours).

       See   also:   delay_notice_recipient,	notify_classes,	   confirm_de-
       lay_cleared.

deliver_lock_attempts (default:	20)
       The  maximal number of attempts to acquire an exclusive lock on a mail-
       box file	or bounce(8) logfile.

deliver_lock_delay (default: 1s)
       The time	between	attempts to acquire an exclusive  lock	on  a  mailbox
       file or bounce(8) logfile.

       Specify	a  non-zero  time  value  (an  integral	value plus an optional
       one-letter suffix that specifies	the time unit).	 Time units:  s	 (sec-
       onds),  m  (minutes), h (hours),	d (days), w (weeks).  The default time
       unit is s (seconds).

destination_concurrency_feedback_debug (default: no)
       Make the	queue manager's	feedback  algorithm  verbose  for  performance
       analysis	purposes.

       This feature is available in Postfix 2.5	and later.

detect_8bit_encoding_header (default: yes)
       Automatically detect 8BITMIME body content by looking at	Content-Trans-
       fer-Encoding:  message  headers;	 historically,	 this	behavior   was
       hard-coded to be	"always	on".

       This feature is available in Postfix 2.5	and later.

disable_dns_lookups (default: no)
       Disable	DNS  lookups  in  the Postfix SMTP and LMTP clients. When dis-
       abled, hosts are	looked up with the getaddrinfo() system	 library  rou-
       tine which normally also	looks in /etc/hosts.  As of Postfix 2.11, this
       parameter is deprecated;	use smtp_dns_support_level instead.

       DNS lookups are enabled by default.

disable_mime_input_processing (default:	no)
       Turn off	MIME processing	while receiving	mail. This means that no  spe-
       cial  treatment is given	to Content-Type: message headers, and that all
       text after the initial message headers is considered to be part of  the
       message body.

       This feature is available in Postfix 2.0	and later.

       Mime  input processing is enabled by default, and is needed in order to
       recognize MIME headers in message content.

disable_mime_output_conversion (default: no)
       Disable the conversion of 8BITMIME format to 7BIT format.  Mime	output
       conversion  is  needed when the destination does	not advertise 8BITMIME
       support.

       This feature is available in Postfix 2.0	and later.

disable_verp_bounces (default: no)
       Disable sending one bounce report per recipient.

       The default, one	per recipient, is what ezmlm needs.

       This feature is available in Postfix 1.1	and later.

disable_vrfy_command (default: no)
       Disable the SMTP	VRFY command. This stops some techniques used to  har-
       vest email addresses.

       Example:

       disable_vrfy_command = no

dns_ncache_ttl_fix_enable (default: no)
       Enable a	workaround for future libc incompatibility. The	Postfix	imple-
       mentation of RFC	2308 negative reply caching relies on the promise that
       res_query()  and	 res_search()  invoke  res_send(),  which  returns the
       server response in an application buffer	even if	the  requested	record
       does  not  exist.  If this promise is broken, specify "yes" to enable a
       workaround for DNS reputation lookups.

       This feature is available in Postfix 3.1	and later.

dnsblog_reply_delay (default: 0s)
       A debugging aid to artificially delay DNS responses.

       This feature is available in Postfix 2.8.

dnsblog_service_name (default: dnsblog)
       The name	of the dnsblog(8) service entry	 in  master.cf.	 This  service
       performs	DNS allow/denylist lookups.

       This feature is available in Postfix 2.8	and later.

dnssec_probe (default: ns:.)
       The  DNS	 query	type (default: "ns") and DNS query name	(default: ".")
       that Postfix may	use to determine whether DNSSEC	validation  is	avail-
       able.

       Background:  DNSSEC validation is needed	for Postfix DANE support; this
       ensures that Postfix receives TLSA records with secure TLS server  cer-
       tificate	 info.	When DNSSEC validation is unavailable, mail deliveries
       using opportunistic DANE	will not be protected  by  server  certificate
       info in TLSA records, and mail deliveries using mandatory DANE will not
       be made at all.

       By default, a Postfix process will send a DNSSEC	 probe	after  1)  the
       process	made  a	 DNS  query  that  requested DNSSEC validation,	2) the
       process did not receive a DNSSEC	validated response to this query or to
       an  earlier  query,  and	 3)  the process did not already send a	DNSSEC
       probe.

       When the	DNSSEC probe has no response, or  when	the  response  is  not
       DNSSEC  validated, Postfix logs a warning that DNSSEC validation	may be
       unavailable.

       Example:

       warning:	DNSSEC validation may be unavailable
       warning:	reason:	dnssec_probe 'ns:.' received a response	that is	not DNSSEC validated
       warning:	reason:	dnssec_probe 'ns:.' received no	response: Server failure

       Possible	reasons	why DNSSEC validation may be unavailable:

       o      The local	/etc/resolv.conf file specifies	a  DNS	resolver  that
	      does   not  validate  DNSSEC  signatures	(that's	 $queue_direc-
	      tory/etc/resolv.conf when	a Postfix  daemon  runs	 in  a	chroot
	      jail).

       o      The local	system library does not	pass on	the "DNSSEC validated"
	      bit to Postfix, or Postfix does not know how to ask the  library
	      to do that.

       By default, the DNSSEC probe asks for the DNS root zone NS records, be-
       cause resolvers should always have that information cached. If  Postfix
       runs  on	 a network where the DNS root zone is not reachable, specify a
       different probe,	or specify an empty dnssec_probe value to disable  the
       feature.

       This  feature  is available in Postfix 3.6 and later. It	was backported
       to Postfix versions 3.5.9, 3.4.19, 3.3.16. 3.2.21.

dont_remove (default: 0)
       Don't remove queue files	and save them to the "saved" mail queue.  This
       is a debugging aid.  To inspect the envelope information	and content of
       a Postfix queue file, use the postcat(1)	command.

double_bounce_sender (default: double-bounce)
       The sender address of postmaster	notifications that  are	 generated  by
       the mail	system.	All mail to this address is silently discarded,	in or-
       der to terminate	mail bounce loops.

duplicate_filter_limit (default: 1000)
       The maximal number of addresses remembered  by  the  address  duplicate
       filter  for  aliases(5)	or virtual(5) alias expansion, or for showq(8)
       queue displays.

empty_address_default_transport_maps_lookup_key	(default: <>)
       The sender_dependent_default_transport_maps search string that will  be
       used instead of the null	sender address.

       This feature is available in Postfix 2.7	and later.

empty_address_local_login_sender_maps_lookup_key (default: <>)
       The lookup key to be used in local_login_sender_maps tables, instead of
       the null	sender address.

       This feature is available in Postfix 3.6	and later.

empty_address_recipient	(default: MAILER-DAEMON)
       The recipient of	mail addressed to the null address.  Postfix does  not
       accept  such  addresses in SMTP commands, but they may still be created
       locally as the result of	configuration or software error.

empty_address_relayhost_maps_lookup_key	(default: <>)
       The sender_dependent_relayhost_maps search string that will be used in-
       stead of	the null sender	address.

       This  feature  is available in Postfix 2.5 and later. With earlier ver-
       sions, sender_dependent_relayhost_maps lookups  were  skipped  for  the
       null sender address.

enable_errors_to (default: no)
       Report mail delivery errors to the address specified with the non-stan-
       dard Errors-To: message header, instead of the envelope sender  address
       (this feature is	removed	with Postfix version 2.2, is turned off	by de-
       fault with Postfix version 2.1, and is  always  turned  on  with	 older
       Postfix versions).

enable_idna2003_compatibility (default:	no)
       Enable 'transitional' compatibility between IDNA2003 and	IDNA2008, when
       converting UTF-8	domain names to/from the ASCII form that is  used  for
       DNS  lookups.  Specify "yes" for	compatibility with Postfix <= 3.1 (not
       recommended). This affects the conversion of domain names that  contain
       for  example  the  German  sz  and  the	Greek  zeta.   See http://uni-
       code.org/cldr/utility/idna.jsp for more examples.

       This feature is available in Postfix 3.2	and later.

enable_long_queue_ids (default:	no)
       Enable long, non-repeating, queue IDs (queue file names).  The  benefit
       of non-repeating	names is simpler logfile analysis and easier queue mi-
       gration (there is no need to run	"postsuper" to change queue file names
       that don't match	their message file inode number).

       Note:  see below	for how	to convert long	queue file names to Postfix <=
       2.8.

       Changing	the parameter value to "yes" has the following effects:

       o      Existing queue file names	are not	affected.

       o      New queue	files are created with names such as  3Pt2mN2VXxznjll.
	      These  are encoded in a 52-character alphabet that contains dig-
	      its (0-9),  upper-case  letters  (B-Z)  and  lower-case  letters
	      (b-z).  For  safety reasons the vowels (AEIOUaeiou) are excluded
	      from the alphabet.  The name format is: 6	or more	characters for
	      the  time	in seconds, 4 characters for the time in microseconds,
	      the 'z'; the remainder is	the file inode number encoded  in  the
	      first 51 characters of the 52-character alphabet.

       o      New messages have	a Message-ID header with queueID@myhostname.

       o      The  mailq  (postqueue  -p)  output has a	wider Queue ID column.
	      The number of whitespace-separated fields	is not changed.

       o      The hash_queue_depth algorithm uses the first characters of  the
	      queue  file creation time	in microseconds, after conversion into
	      hexadecimal representation. This produces	the same queue hashing
	      behavior	as  if	the  queue  file  name	was  created with "en-
	      able_long_queue_ids = no".

       Changing	the parameter value to "no" has	the following effects:

       o      Existing long queue file names are renamed  to  the  short  form
	      (while running "postfix reload" or "postsuper").

       o      New  queue files are created with	names such as C3CD21F3E90 from
	      a	hexadecimal alphabet that contains digits (0-9)	and upper-case
	      letters  (A-F). The name format is: 5 characters for the time in
	      microseconds; the	remainder is the file inode number.

       o      New  messages  have  a  Message-ID   header   with   YYYYMMDDHH-
	      MMSS.queueid@myhostname,	where  YYYYMMDDHHMMSS  are  the	 year,
	      month, day, hour,	minute and second.

       o      The mailq	(postqueue -p) output has  the	same  format  as  with
	      Postfix <= 2.8.

       o      The  hash_queue_depth algorithm uses the first characters	of the
	      queue file name, with the	hexadecimal representation of the file
	      creation time in microseconds.

       Before migration	to Postfix <= 2.8, the following commands are required
       to convert long queue file names	into short names:

       # postfix stop
       # postconf enable_long_queue_ids=no
       # postsuper

       Repeat the postsuper command until it reports no	more queue  file  name
       changes.

       This feature is available in Postfix 2.9	and later.

enable_original_recipient (default: yes)
       Enable  support	for the	original recipient address after an address is
       rewritten to a different	address	(for example  with  aliasing  or  with
       canonical mapping).

       The original recipient address is used as follows:

       Final delivery
	      With  "enable_original_recipient	= yes",	the original recipient
	      address is stored	in  the	 X-Original-To	message	 header.  This
	      header  may  be used to distinguish between different recipients
	      that share the same mailbox.

       Recipient deduplication
	      With "enable_original_recipient =	yes",  the  cleanup(8)	daemon
	      performs duplicate recipient elimination based on	the content of
	      (original	recipient, maybe-rewritten recipient)  pairs.	Other-
	      wise,  the cleanup(8) daemon performs duplicate recipient	elimi-
	      nation based only	on the maybe-rewritten recipient address.

       Note: with Postfix <= 3.2 the "setting enable_original_recipient	=  no"
       breaks address verification for addresses that are aliased or otherwise
       rewritten (Postfix is unable to store the address  verification	result
       under the original probe	destination address; instead, it can store the
       result only under the rewritten address).

       This feature is available in Postfix 2.1	and later. Postfix version 2.0
       behaves	as  if	this parameter is always set to	yes.  Postfix versions
       before 2.0 have no support for the original recipient address.

enable_threaded_bounces	(default: no)
       Enable non-delivery, success, and delay notifications that link to  the
       original	 message  by  including	 a References: and In-Reply-To:	header
       with the	original Message-ID value. There are advantages	and  disadvan-
       tages to	consider.

	advantage
	      This  allows mail	readers	to present a delivery status notifica-
	      tion in the same email thread as the original message.

	disadvantage
	      This makes it easy for users  to	mistakenly  delete  the	 whole
	      email  thread  (all  related messages), instead of deleting only
	      the non-delivery notification.

       This feature is available in Postfix 3.6	and later.

error_notice_recipient (default: postmaster)
       The recipient of	postmaster notifications about mail delivery  problems
       that  are  caused  by  policy,  resource,  software or protocol errors.
       These notifications are enabled with the	notify_classes parameter.

error_service_name (default: error)
       The name	of the error(8)	pseudo delivery	agent. This service always re-
       turns mail as undeliverable.

       This feature is available in Postfix 2.0	and later.

execution_directory_expansion_filter (default: see postconf -d output)
       Restrict	 the  characters  that	the  local(8) delivery agent allows in
       $name expansions	of $command_execution_directory.   Characters  outside
       the allowed set are replaced by underscores.

       This feature is available in Postfix 2.2	and later.

expand_owner_alias (default: no)
       When  delivering	 to an alias "aliasname" that has an "owner-aliasname"
       companion alias,	set the	envelope sender	address	to  the	 expansion  of
       the  "owner-aliasname"  alias.	Normally,  Postfix  sets  the envelope
       sender address to the name of the "owner-aliasname" alias.

export_environment (default: see postconf -d output)
       The list	of environment variables that a	Postfix	process	will export to
       non-Postfix  processes. The TZ variable is needed for sane time keeping
       on System-V-ish systems.

       Specify a list of names and/or name=value pairs,	 separated  by	white-
       space or	comma. Specify "{ name=value }"	to protect whitespace or comma
       in parameter values (whitespace after the opening "{"  and  before  the
       closing	"}" is ignored). The form name=value is	supported with Postfix
       version 2.1 and later; the use of {} is supported with Postfix 3.0  and
       later.

       Example:

       export_environment = TZ PATH=/bin:/usr/bin

extract_recipient_limit	(default: 10240)
       The  maximal  number  of	 recipient addresses that Postfix will extract
       from message headers when mail is submitted with	"sendmail -t".

       This feature was	removed	in Postfix version 2.1.

fallback_relay (default: empty)
       Optional	list of	relay hosts for	SMTP destinations that can't be	 found
       or  that	are unreachable. With Postfix 2.3 this parameter is renamed to
       smtp_fallback_relay.

       By default, mail	is returned to the sender when a  destination  is  not
       found, and delivery is deferred when a destination is unreachable.

       The  fallback relays must be SMTP destinations. Specify a domain, host,
       host:port, [host]:port, [address] or [address]:port;  the  form	[host]
       turns off MX lookups.  If you specify multiple SMTP destinations, Post-
       fix will	try them in the	specified order.

       Note: before Postfix 2.2, do not	use the	 fallback_relay	 feature  when
       relaying	 mail  for  a backup or	primary	MX domain. Mail	would loop be-
       tween the Postfix MX host and the fallback_relay	host  when  the	 final
       destination is unavailable.

       o      In main.cf specify "relay_transport = relay",

       o      In  master.cf specify "-o	fallback_relay =" (i.e., empty)	at the
	      end of the relay entry.

       o      In transport maps, specify "relay:nexthop..."  as	the right-hand
	      side for backup or primary MX domain entries.

       Postfix	version	 2.2 and later will not	use the	fallback_relay feature
       for destinations	that it	is MX host for.

fallback_transport (default: empty)
       Optional	message	delivery transport that	the  local(8)  delivery	 agent
       should use for names that are not found in the aliases(5) or UNIX pass-
       word database.

       The precedence of local(8) delivery  features  from  high  to  low  is:
       aliases,	 .forward  files,  mailbox_transport_maps,  mailbox_transport,
       mailbox_command_maps, mailbox_command, home_mailbox,  mail_spool_direc-
       tory, fallback_transport_maps, fallback_transport and luser_relay.

fallback_transport_maps	(default: empty)
       Optional	 lookup	 tables	with per-recipient message delivery transports
       for recipients that the local(8)	delivery agent could not find  in  the
       aliases(5) or UNIX password database.

       The  precedence	of  local(8)  delivery	features  from high to low is:
       aliases,	 .forward  files,  mailbox_transport_maps,  mailbox_transport,
       mailbox_command_maps,  mailbox_command, home_mailbox, mail_spool_direc-
       tory, fallback_transport_maps, fallback_transport and luser_relay.

       For safety reasons, this	feature	does not allow	$number	 substitutions
       in regular expression maps.

       This feature is available in Postfix 2.3	and later.

fast_flush_domains (default: $relay_domains)
       Optional	 list  of  destinations	 that are eligible for per-destination
       logfiles	with mail that is queued to those destinations.

       By default, Postfix maintains "fast flush" logfiles only	 for  destina-
       tions that the Postfix SMTP server is willing to	relay to (i.e. the de-
       fault is: "fast_flush_domains = $relay_domains";	see the	 relay_domains
       parameter in the	postconf(5) manual).

       Specify	a list of hosts	or domains, "/file/name" patterns or "type:ta-
       ble" lookup tables, separated by	commas	and/or	whitespace.   Continue
       long  lines  by	starting the next line with whitespace.	A "/file/name"
       pattern is replaced by its contents; a  "type:table"  lookup  table  is
       matched when the	domain or its parent domain appears as lookup key.

       Pattern	matching  of domain names is controlled	by the presence	or ab-
       sence of	"fast_flush_domains" in	 the  parent_domain_matches_subdomains
       parameter value.

       Specify "fast_flush_domains =" (i.e., empty) to disable the feature al-
       together.

fast_flush_purge_time (default:	7d)
       The time	after which an empty per-destination "fast flush"  logfile  is
       deleted.

       You can specify the time	as a number, or	as a number followed by	a let-
       ter that	 indicates  the	 time  unit:  s=seconds,  m=minutes,  h=hours,
       d=days, w=weeks.	 The default time unit is days.

fast_flush_refresh_time	(default: 12h)
       The  time  after	 which	a  non-empty  but unread per-destination "fast
       flush" logfile needs to be refreshed.  The contents of  a  logfile  are
       refreshed by requesting delivery	of all messages	listed in the logfile.

       You can specify the time	as a number, or	as a number followed by	a let-
       ter that	 indicates  the	 time  unit:  s=seconds,  m=minutes,  h=hours,
       d=days, w=weeks.	 The default time unit is hours.

fault_injection_code (default: 0)
       Force  specific	internal tests to fail,	to test	the handling of	errors
       that are	difficult to reproduce otherwise.

flush_service_name (default: flush)
       The name	of the flush(8)	service. This service  maintains  per-destina-
       tion  logfiles  with  the  queue	 file names of mail that is queued for
       those destinations.

       This feature is available in Postfix 2.0	and later.

fork_attempts (default:	5)
       The maximal number of attempts to fork()	a child	process.

fork_delay (default: 1s)
       The delay between attempts to fork() a child process.

       Specify a non-zero time value  (an  integral  value  plus  an  optional
       one-letter  suffix  that	specifies the time unit).  Time	units: s (sec-
       onds), m	(minutes), h (hours), d	(days),	w (weeks).  The	 default  time
       unit is s (seconds).

forward_expansion_filter (default: see postconf	-d output)
       Restrict	 the  characters  that	the  local(8) delivery agent allows in
       $name expansions	of $forward_path.  Characters outside the allowed  set
       are replaced by underscores.

forward_path (default: see postconf -d output)
       The  local(8)  delivery	agent  search list for finding a .forward file
       with user-specified delivery methods. The first file that is  found  is
       used.

       The  forward_path value is not subject to Postfix configuration parame-
       ter $name expansion. Instead, the following $name expansions  are  done
       on  forward_path	 before	 the  search  actually happens.	 The result of
       $name expansion is filtered with	the character set  that	 is  specified
       with the	forward_expansion_filter parameter.

       $user  The recipient's username.

       $shell The recipient's login shell pathname.

       $home  The recipient's home directory.

       $recipient
	      The full recipient address.

       $extension
	      The optional recipient address extension.

       $domain
	      The recipient domain.

       $local The entire recipient localpart.

       $recipient_delimiter
	      The  address extension delimiter that was	found in the recipient
	      address (Postfix 2.11 and	later),	or the	system-wide  recipient
	      address extension	delimiter (Postfix 2.10	and earlier).

       ${name?value}

       ${name?{value}} (Postfix	>= 3.0)
	      Expands to value when $name is non-empty.

       ${name:value}

       ${name:{value}} (Postfix	>= 3.0)
	      Expands to value when $name is empty.

       ${name?{value1}:{value2}} (Postfix >= 3.0)
	      Expands to value1	when $name is non-empty, value2	otherwise.

       Instead of $name	you can	also specify ${name} or	$(name).

       Examples:

       forward_path = /var/forward/$user
       forward_path =
	   /var/forward/$user/.forward$recipient_delimiter$extension,
	   /var/forward/$user/.forward

frozen_delivered_to (default: yes)
       Update  the local(8) delivery agent's idea of the Delivered-To: address
       (see prepend_delivered_header) only once, at the	start  of  a  delivery
       attempt;	 do  not  update  the  Delivered-To:  address  while expanding
       aliases or .forward files.

       This feature is available in Postfix 2.3	and later. With	older  Postfix
       releases,  the behavior is as if	this parameter is set to "no". The old
       setting can be expensive	with deeply nested aliases or .forward	files.
       When  an	 alias	or .forward file changes the Delivered-To: address, it
       ties up one queue file and one cleanup process instance while  mail  is
       being forwarded.

hash_queue_depth (default: 1)
       The number of subdirectory levels for queue directories listed with the
       hash_queue_names	parameter. Queue hashing is  implemented  by  creating
       one  or	more  levels  of directories with one-character	names.	Origi-
       nally, these directory names were equal to the first characters of  the
       queue  file  name, with the hexadecimal representation of the file cre-
       ation time in microseconds.

       With long queue file names, queue hashing produces the same results  as
       with  short  names. The file creation time in microseconds is converted
       into hexadecimal	form before the	result is used for queue hashing.  The
       base  16	encoding gives finer control over the number of	subdirectories
       than is possible	with the base 52 encoding of long queue	file names.

       After changing the hash_queue_names or hash_queue_depth parameter, exe-
       cute the	command	"postfix reload".

hash_queue_names (default: deferred, defer)
       The names of queue directories that are split across multiple subdirec-
       tory levels.

       Before Postfix version 2.2, the default list of hashed queues was  sig-
       nificantly  larger. Claims about	improvements in	file system technology
       suggest that hashing of the incoming and	active	queues	is  no	longer
       needed.	Fewer  hashed  directories speed up the	time needed to restart
       Postfix.

       After changing the hash_queue_names or hash_queue_depth parameter, exe-
       cute the	command	"postfix reload".

header_address_token_limit (default: 10240)
       The  maximal number of address tokens are allowed in an address message
       header. Information that	exceeds	the limit is discarded.	 The limit  is
       enforced	by the cleanup(8) server.

header_checks (default:	empty)
       Optional	 lookup	tables for content inspection of primary non-MIME mes-
       sage headers, as	specified in the header_checks(5) manual page.

header_from_format (default: standard)
       The format of the Postfix-generated From: header. This setting  affects
       the  appearance of 'full	name' information when a local program such as
       /bin/mail submits a message without a From: header through the  Postfix
       sendmail(1) command.

       Specify one of the following:

       standard	(default)
	      Produce  a  header formatted as "From: name <address>".  This is
	      the default as of	Postfix	3.3.

       obsolete
	      Produce a	header formatted as "From: address  (name)".  This  is
	      the behavior prior to Postfix 3.3.

       Notes:

       o      Postfix  generates the format "From: address" when name informa-
	      tion is unavailable or the envelope  sender  address  is	empty.
	      This is the same behavior	as prior to Postfix 3.3.

       o      In  the  standard	 form,	the name will be quoted	if it contains
	      specials as defined in RFC 5322, or the "!%" address operators.

       o      The Postfix sendmail(1) command gets name	information  from  the
	      -F  command-line	option,	from the NAME environment variable, or
	      from the UNIX password file.

       This feature is available in Postfix 3.3	and later.

header_size_limit (default: 102400)
       The maximal amount of memory in bytes for storing a message header.  If
       a  header is larger, the	excess is discarded.  The limit	is enforced by
       the cleanup(8) server.

helpful_warnings (default: yes)
       Log warnings about  problematic	configuration  settings,  and  provide
       helpful suggestions.

       This feature is available in Postfix 2.0	and later.

home_mailbox (default: empty)
       Optional	 pathname of a mailbox file relative to	a local(8) user's home
       directory.

       Specify a pathname ending in "/"	for qmail-style	delivery.

       The precedence of local(8) delivery  features  from  high  to  low  is:
       aliases,	 .forward  files,  mailbox_transport_maps,  mailbox_transport,
       mailbox_command_maps, mailbox_command, home_mailbox,  mail_spool_direc-
       tory, fallback_transport_maps, fallback_transport and luser_relay.

       Examples:

       home_mailbox = Mailbox
       home_mailbox = Maildir/

hopcount_limit (default: 50)
       The maximal number of Received:	message	headers	that is	allowed	in the
       primary message headers.	A message that exceeds the limit  is  bounced,
       in order	to stop	a mailer loop.

html_directory (default: see postconf -d output)
       The  location of	Postfix	HTML files that	describe how to	build, config-
       ure or operate a	specific Postfix subsystem or feature.

ignore_mx_lookup_error (default: no)
       Ignore DNS MX lookups that produce no response.	By default, the	 Post-
       fix SMTP	client defers delivery and tries again after some delay.  This
       behavior	is required by the SMTP	standard.

       Specify "ignore_mx_lookup_error = yes" to force a DNS A	record	lookup
       instead.	This violates the SMTP standard	and can	result in mis-delivery
       of mail.

import_environment (default: see postconf -d output)
       The list	of environment variables that  a  privileged  Postfix  process
       will  import  from a non-Postfix	parent process,	or name=value environ-
       ment overrides.	Unprivileged utilities	will  enforce  the  name=value
       overrides,  but	otherwise  will	 not change their process environment.
       Examples	of relevant environment	variables:

       TZ     May be needed for	sane time keeping on  most  System-V-ish  sys-
	      tems.

       DISPLAY
	      Needed for debugging Postfix daemons with	an X-windows debugger.

       XAUTHORITY
	      Needed for debugging Postfix daemons with	an X-windows debugger.

       MAIL_CONFIG
	      Needed to	make "postfix -c" work.

       Specify	a  list	 of names and/or name=value pairs, separated by	white-
       space or	comma. Specify "{ name=value }"	to protect whitespace or comma
       in  environment	variable  values (whitespace after the opening "{" and
       before the closing "}" is ignored). The form  name=value	 is  supported
       with  Postfix  version  2.1  and	later; the use of {} is	supported with
       Postfix 3.0 and later.

in_flow_delay (default:	1s)
       Time to pause before accepting a	new message, when the message  arrival
       rate  exceeds  the  message delivery rate. This feature is turned on by
       default (it's disabled on SCO UNIX due to an SCO	bug).

       With the	default	100 Postfix SMTP server	process	limit,	"in_flow_delay
       =  1s" limits the mail inflow to	100 messages per second	above the num-
       ber of messages delivered per second.

       Specify 0 to disable the	feature. Valid delays are 0..10.

inet_interfaces	(default: all)
       The network interface addresses that this mail system receives mail on.
       Specify	"all" to receive mail on all network interfaces	(default), and
       "loopback-only" to receive mail on  loopback  network  interfaces  only
       (Postfix	 version 2.2 and later).  The parameter	also controls delivery
       of mail to user@[ip.address].

       Note 1: you need	to stop	and start Postfix when this parameter changes.

       Note 2: address information may be enclosed inside [], but this form is
       not required here.

       When  inet_interfaces  specifies	just one IPv4 and/or IPv6 address that
       is not a	loopback address, the Postfix SMTP client will	use  this  ad-
       dress  as  the IP source	address	for outbound mail. Support for IPv6 is
       available in Postfix version 2.2	and later.

       On a multi-homed	firewall with separate Postfix instances listening  on
       the  "inside"  and "outside" interfaces,	this can prevent each instance
       from being able to reach	remote SMTP servers on the "other side"	of the
       firewall.  Setting  smtp_bind_address  to  0.0.0.0 avoids the potential
       problem for IPv4, and setting smtp_bind_address6	to :: solves the prob-
       lem for IPv6.

       A better	solution for multi-homed firewalls is to leave inet_interfaces
       at the default value and	instead	use explicit IP	addresses in the  mas-
       ter.cf  SMTP  server  definitions.   This  preserves  the  Postfix SMTP
       client's	loop detection,	by ensuring that each  side  of	 the  firewall
       knows  that  the	 other	IP  address  is	 still	the same host. Setting
       $inet_interfaces	to a single IPv4 and/or	IPV6 address is	primarily use-
       ful  with  virtual  hosting  of domains on secondary IP addresses, when
       each IP address serves a	different domain (and has a different $myhost-
       name setting).

       See also	the proxy_interfaces parameter,	for network addresses that are
       forwarded to Postfix by way of a	proxy or address translator.

       Examples:

       inet_interfaces = all (DEFAULT)
       inet_interfaces = loopback-only (Postfix	version	2.2 and	later)
       inet_interfaces = 127.0.0.1
       inet_interfaces = 127.0.0.1, [::1] (Postfix version 2.2 and later)
       inet_interfaces = 192.168.1.2, 127.0.0.1

inet_protocols (default: see 'postconf -d output')
       The Internet protocols Postfix will attempt to use when making  or  ac-
       cepting connections. Specify one	or more	of "ipv4" or "ipv6", separated
       by whitespace or	commas.	The form "all" is equivalent to	 "ipv4,	 ipv6"
       or "ipv4", depending on whether the operating system implements IPv6.

       With  Postfix 2.8 and earlier the default is "ipv4". For	backwards com-
       patibility with these releases, the Postfix 2.9 and later upgrade  pro-
       cedure  appends	an explicit "inet_protocols = ipv4" setting to main.cf
       when no explicit	setting	is present. This compatibility workaround will
       be phased out as	IPv6 deployment	becomes	more common.

       This feature is available in Postfix 2.2	and later.

       Note: you MUST stop and start Postfix after changing this parameter.

       On systems that pre-date	IPV6_V6ONLY support (RFC 3493),	an IPv6	server
       will also accept	IPv4 connections, even when IPv4 is  turned  off  with
       the  inet_protocols  parameter.	 On  systems with IPV6_V6ONLY support,
       Postfix will use	separate server	sockets	for IPv6 and  IPv4,  and  each
       will accept only	connections for	the corresponding protocol.

       When  IPv4 support is enabled via the inet_protocols parameter, Postfix
       will look up DNS	type A records,	and will convert  IPv4-in-IPv6	client
       IP  addresses  (::ffff:1.2.3.4)	to their original IPv4 form (1.2.3.4).
       The latter is needed on hosts that pre-date  IPV6_V6ONLY	 support  (RFC
       3493).

       When  IPv6 support is enabled via the inet_protocols parameter, Postfix
       will do DNS type	AAAA record lookups.

       When both IPv4 and IPv6 support are enabled, the	 Postfix  SMTP	client
       will  choose the	protocol as specified with the smtp_address_preference
       parameter. Postfix versions before 2.8 attempt to connect via IPv6  be-
       fore attempting to use IPv4.

       Examples:

       inet_protocols =	ipv4
       inet_protocols =	all (DEFAULT)
       inet_protocols =	ipv6
       inet_protocols =	ipv4, ipv6

info_log_address_format	(default: external)
       The  email  address  form that will be used in non-debug	logging	(info,
       warning,	etc.). As of Postfix 3.5 when an  address  localpart  contains
       spaces  or  other special characters, the localpart will	be quoted, for
       example:

	       from=<"name with	spaces"@example.com>

       Older Postfix versions would log	the internal (unquoted)	form:

	       from=<name with spaces@example.com>

       The external and	internal forms are identical for the vast majority  of
       email  addresses	 that contain no spaces	or other special characters in
       the localpart.

       The logging in external form is consistent with the address  form  that
       Postfix	3.2 and	later prefer for most table lookups. This is therefore
       the more	useful form for	non-debug logging.

       Specify "info_log_address_format	= internal" for	backwards  compatibil-
       ity.

       Postfix	uses  the  unquoted  form  internally, because an attacker can
       specify an email	address	in  different  forms  by  playing  games  with
       quotes  and  backslashes.  An  attacker	should not be able to use such
       games to	circumvent Postfix access policies.

       This feature is available in Postfix 3.5	and later.

initial_destination_concurrency	(default: 5)
       The initial per-destination concurrency level for parallel delivery  to
       the same	destination.  With per-destination recipient limit > 1,	a des-
       tination	is a domain, otherwise it is a recipient.

       Use  transport_initial_destination_concurrency  to  specify  a	trans-
       port-specific  override,	 where	transport is the master.cf name	of the
       message delivery	transport (Postfix 2.5 and later).

       Warning:	with concurrency of 1, one bad message can be enough to	 block
       all mail	to a site.

internal_mail_filter_classes (default: empty)
       What  categories	 of Postfix-generated mail are subject to before-queue
       content inspection by non_smtpd_milters,	header_checks and body_checks.
       Specify	zero  or  more	of  the	 following, separated by whitespace or
       comma.

       bounce Inspect the content of delivery status notifications.

       notify Inspect the content of postmaster	notifications by  the  smtp(8)
	      and smtpd(8) processes.

       NOTE:  It's  generally  not  safe to enable content inspection of Post-
       fix-generated email messages. The user is warned.

       This feature is available in Postfix 2.3	and later.

invalid_hostname_reject_code (default: 501)
       The numerical Postfix SMTP server response code when the	client HELO or
       EHLO  command parameter is rejected by the reject_invalid_helo_hostname
       restriction.

       Do not change this unless you have  a  complete	understanding  of  RFC
       5321.

ipc_idle (default: version dependent)
       The  time  after	 which	a client closes	an idle	internal communication
       channel.	 The purpose is	to allow Postfix daemon	processes to terminate
       voluntarily  after  they	become idle. This is used, for example,	by the
       Postfix address resolving and rewriting clients.

       With Postfix 2.4	the default value was reduced from 100s	to 5s.

       Specify a non-zero time value  (an  integral  value  plus  an  optional
       one-letter  suffix  that	specifies the time unit).  Time	units: s (sec-
       onds), m	(minutes), h (hours), d	(days),	w (weeks).  The	 default  time
       unit is s (seconds).

ipc_timeout (default: 3600s)
       The  time  limit	 for sending or	receiving information over an internal
       communication channel.  The purpose is to break out of deadlock	situa-
       tions.  If  the time limit is exceeded the software aborts with a fatal
       error.

       Specify a non-zero time value  (an  integral  value  plus  an  optional
       one-letter  suffix  that	specifies the time unit).  Time	units: s (sec-
       onds), m	(minutes), h (hours), d	(days),	w (weeks).  The	 default  time
       unit is s (seconds).

ipc_ttl	(default: 1000s)
       The  time  after	which a	client closes an active	internal communication
       channel.	 The purpose is	to allow Postfix daemon	processes to terminate
       voluntarily after reaching their	client limit.  This is used, for exam-
       ple, by the Postfix address resolving and rewriting clients.

       Specify a non-zero time value  (an  integral  value  plus  an  optional
       one-letter  suffix  that	specifies the time unit).  Time	units: s (sec-
       onds), m	(minutes), h (hours), d	(days),	w (weeks).  The	 default  time
       unit is s (seconds).

       This feature is available in Postfix 2.1	and later.

known_tcp_ports	 (default:  lmtp=24,  smtp=25,	smtps=submissions=465, submis-
       sion=587)
       Optional	setting	that avoids lookups in the services(5) database.  This
       feature	was  implemented to address inconsistencies in the name	of the
       port "465" service. The ABNF is:

	   known_tcp_ports = empty | name-to-port *(","	name-to-port)
	   name-to-port	= 1*(service-name "=') port-number

       The comma is required. Whitespace is optional but it cannot appear  in-
       side a service name or port number.

       This feature is available in Postfix 3.6	and later.

line_length_limit (default: 2048)
       Upon  input,  long  lines  are  chopped	up into	pieces of at most this
       length; upon delivery, long lines are reconstructed.

lmdb_map_size (default:	16777216)
       The initial OpenLDAP LMDB database size limit in	bytes.	 Each  time  a
       database	becomes	full, its size limit is	doubled.

       This feature is available in Postfix 2.11 and later.

lmtp_address_preference	(default: ipv6)
       The  LMTP-specific version of the smtp_address_preference configuration
       parameter.  See there for details.

       This feature is available in Postfix 2.8	and later.

lmtp_address_verify_target (default: rcpt)
       The LMTP-specific version of the	smtp_address_verify_target  configura-
       tion parameter.	See there for details.

       This feature is available in Postfix 3.0	and later.

lmtp_assume_final (default: no)
       When  a	remote	LMTP  server announces no DSN support, assume that the
       server performs final delivery, and send	 "delivered"  delivery	status
       notifications  instead  of  "relayed". The default setting is backwards
       compatible to avoid the infinitesimal possibility of breaking  existing
       LMTP-based content filters.

lmtp_balance_inet_protocols (default: yes)
       The LMTP-specific version of the	smtp_balance_inet_protocols configura-
       tion parameter. See there for details.

       This feature is available in Postfix 3.3	and later.

lmtp_bind_address (default: empty)
       The LMTP-specific version of the	smtp_bind_address configuration	param-
       eter.  See there	for details.

       This feature is available in Postfix 2.3	and later.

lmtp_bind_address6 (default: empty)
       The  LMTP-specific  version of the smtp_bind_address6 configuration pa-
       rameter.	 See there for details.

       This feature is available in Postfix 2.3	and later.

lmtp_bind_address_enforce (default: empty)
       The LMTP-specific version of the	 smtp_bind_address_enforce  configura-
       tion parameter. See there for details.

       This feature is available in Postfix 3.7	and later.

lmtp_body_checks (default: empty)
       The LMTP-specific version of the	smtp_body_checks configuration parame-
       ter. See	there for details.

       This feature is available in Postfix 2.5	and later.

lmtp_cache_connection (default:	yes)
       Keep Postfix LMTP client	connections open for up	to $max_idle  seconds.
       When  the  LMTP	client	receives a request for the same	connection the
       connection is reused.

       This parameter is available in Postfix version 2.2 and  earlier.	  With
       Postfix	version	 2.3  and  later, see lmtp_connection_cache_on_demand,
       lmtp_connection_cache_destinations,	 or	   lmtp_connection_re-
       use_time_limit.

       The  effectiveness of cached connections	will be	determined by the num-
       ber of remote LMTP servers in use, and the concurrency limit  specified
       for the Postfix LMTP client. Cached connections are closed under	any of
       the following conditions:

       o      The Postfix LMTP client idle time	limit is reached.  This	 limit
	      is specified with	the Postfix max_idle configuration parameter.

       o      A	 delivery  request  specifies a	different destination than the
	      one currently cached.

       o      The per-process limit on the  number  of	delivery  requests  is
	      reached.	 This limit is specified with the Postfix max_use con-
	      figuration parameter.

       o      Upon the onset of	another	 delivery  request,  the  remote  LMTP
	      server  associated  with the current session does	not respond to
	      the RSET command.

       Most of these limitations have been with	the Postfix  connection	 cache
       that is shared among multiple LMTP client programs.

lmtp_cname_overrides_servername	(default: yes)
       The  LMTP-specific  version of the smtp_cname_overrides_servername con-
       figuration parameter.  See there	for details.

       This feature is available in Postfix 2.3	and later.

lmtp_connect_timeout (default: 0s)
       The Postfix LMTP	client time limit for completing a TCP connection,  or
       zero  (use  the operating system	built-in time limit).  When no connec-
       tion can	be made	within the deadline, the LMTP client  tries  the  next
       address on the mail exchanger list.

       Specify	a  non-negative	time value (an integral	value plus an optional
       one-letter suffix that specifies	the time unit).	 Time units:  s	 (sec-
       onds),  m  (minutes), h (hours),	d (days), w (weeks).  The default time
       unit is s (seconds).

       Example:

       lmtp_connect_timeout = 30s

lmtp_connection_cache_destinations (default: empty)
       The LMTP-specific  version  of  the  smtp_connection_cache_destinations
       configuration parameter.	 See there for details.

       This feature is available in Postfix 2.3	and later.

lmtp_connection_cache_on_demand	(default: yes)
       The  LMTP-specific  version of the smtp_connection_cache_on_demand con-
       figuration parameter.  See there	for details.

       This feature is available in Postfix 2.3	and later.

lmtp_connection_cache_time_limit (default: 2s)
       The LMTP-specific version of the	smtp_connection_cache_time_limit  con-
       figuration parameter.  See there	for details.

       This feature is available in Postfix 2.3	and later.

lmtp_connection_reuse_count_limit (default: 0)
       The LMTP-specific version of the	smtp_connection_reuse_count_limit con-
       figuration parameter.  See there	for details.

       This feature is available in Postfix 2.11 and later.

lmtp_connection_reuse_time_limit (default: 300s)
       The LMTP-specific version of the	smtp_connection_reuse_time_limit  con-
       figuration parameter.  See there	for details.

       This feature is available in Postfix 2.3	and later.

lmtp_data_done_timeout (default: 600s)
       The  Postfix  LMTP  client time limit for sending the LMTP ".", and for
       receiving the remote LMTP server	response.  When	 no  response  is  re-
       ceived  within  the  deadline, a	warning	is logged that the mail	may be
       delivered multiple times.

       Specify a non-zero time value  (an  integral  value  plus  an  optional
       one-letter  suffix  that	specifies the time unit).  Time	units: s (sec-
       onds), m	(minutes), h (hours), d	(days),	w (weeks).  The	 default  time
       unit is s (seconds).

lmtp_data_init_timeout (default: 120s)
       The  Postfix  LMTP client time limit for	sending	the LMTP DATA command,
       and for receiving the remote LMTP server	response.

       Specify a non-zero time value  (an  integral  value  plus  an  optional
       one-letter  suffix  that	specifies the time unit).  Time	units: s (sec-
       onds), m	(minutes), h (hours), d	(days),	w (weeks).  The	 default  time
       unit is s (seconds).

lmtp_data_xfer_timeout (default: 180s)
       The  Postfix  LMTP  client time limit for sending the LMTP message con-
       tent.  When the connection stalls for more than $lmtp_data_xfer_timeout
       the LMTP	client terminates the transfer.

       Specify	a  non-zero  time  value  (an  integral	value plus an optional
       one-letter suffix that specifies	the time unit).	 Time units:  s	 (sec-
       onds),  m  (minutes), h (hours),	d (days), w (weeks).  The default time
       unit is s (seconds).

lmtp_defer_if_no_mx_address_found (default: no)
       The LMTP-specific version of the	smtp_defer_if_no_mx_address_found con-
       figuration parameter.  See there	for details.

       This feature is available in Postfix 2.3	and later.

lmtp_delivery_status_filter (default: empty)
       The LMTP-specific version of the	smtp_delivery_status_filter configura-
       tion parameter.	See there for details.

       This feature is available in Postfix 3.0	and later.

lmtp_destination_concurrency_limit   (default:	  $default_destination_concur-
       rency_limit)
       The  maximal  number of parallel	deliveries to the same destination via
       the lmtp	message	delivery transport. This  limit	 is  enforced  by  the
       queue  manager.	The message delivery transport name is the first field
       in the entry in the master.cf file.

lmtp_destination_recipient_limit    (default:	  $default_destination_recipi-
       ent_limit)
       The  maximal  number of recipients per message for the lmtp message de-
       livery transport. This limit is enforced	by the queue manager. The mes-
       sage  delivery  transport  name	is the first field in the entry	in the
       master.cf file.

       Setting this parameter to a value of 1 changes the meaning of lmtp_des-
       tination_concurrency_limit from concurrency per domain into concurrency
       per recipient.

lmtp_discard_lhlo_keyword_address_maps (default: empty)
       Lookup tables, indexed by the remote LMTP server	address, with case in-
       sensitive  lists	 of  LHLO  keywords (pipelining, starttls, auth, etc.)
       that the	Postfix	LMTP client will ignore	in the LHLO  response  from  a
       remote LMTP server. See lmtp_discard_lhlo_keywords for details. The ta-
       ble  is	not  indexed  by  hostname  for	 consistency  with  smtpd_dis-
       card_ehlo_keyword_address_maps.

       This feature is available in Postfix 2.3	and later.

lmtp_discard_lhlo_keywords (default: empty)
       A  case	insensitive list of LHLO keywords (pipelining, starttls, auth,
       etc.) that the Postfix LMTP client will ignore  in  the	LHLO  response
       from a remote LMTP server.

       This feature is available in Postfix 2.3	and later.

       Notes:

       o      Specify the silent-discard pseudo	keyword	to prevent this	action
	      from being logged.

       o      Use the lmtp_discard_lhlo_keyword_address_maps feature  to  dis-
	      card LHLO	keywords selectively.

lmtp_dns_reply_filter (default:	empty)
       Optional	 filter	 for  Postfix  LMTP  client  DNS  lookup results.  See
       smtp_dns_reply_filter for details including an example.

       This feature is available in Postfix 3.0	and later.

lmtp_dns_resolver_options (default: empty)
       The LMTP-specific version of the	 smtp_dns_resolver_options  configura-
       tion parameter.	See there for details.

       This feature is available in Postfix 2.8	and later.

lmtp_dns_support_level (default: empty)
       The  LMTP-specific  version of the smtp_dns_support_level configuration
       parameter.  See there for details.

       This feature is available in Postfix 2.11 and later.

lmtp_enforce_tls (default: no)
       The LMTP-specific version of the	smtp_enforce_tls configuration parame-
       ter.  See there for details.

       This feature is available in Postfix 2.3	and later.

lmtp_fallback_relay (default: empty)
       Optional	 list of relay hosts for LMTP destinations that	can't be found
       or that are unreachable.	 In main.cf elements are separated  by	white-
       space or	commas.

       By  default,  mail  is returned to the sender when a destination	is not
       found, and delivery is deferred when a destination is unreachable.

       The fallback relays must	be TCP destinations, specified without a lead-
       ing  "inet:" prefix.  Specify a host or host:port.  Since MX lookups do
       not apply  with	LMTP,  there  is  no  need  to	use  the  "[host]"  or
       "[host]:port"  forms.  If you specify multiple LMTP destinations, Post-
       fix will	try them in the	specified order.

       This feature is available in Postfix 3.1	and later.

lmtp_generic_maps (default: empty)
       The LMTP-specific version of the	smtp_generic_maps configuration	param-
       eter.  See there	for details.

       This feature is available in Postfix 2.3	and later.

lmtp_header_checks (default: empty)
       The  LMTP-specific  version of the smtp_header_checks configuration pa-
       rameter.	See there for details.

       This feature is available in Postfix 2.5	and later.

lmtp_host_lookup (default: dns)
       The LMTP-specific version of the	smtp_host_lookup configuration parame-
       ter.  See there for details.

       This feature is available in Postfix 2.3	and later.

lmtp_lhlo_name (default: $myhostname)
       The hostname to send in the LMTP	LHLO command.

       The  default  value  is	the  machine  hostname.	 Specify a hostname or
       [ip.add.re.ss] or [ip:v6:add:re::ss].

       This information	can be specified in the	 main.cf  file	for  all  LMTP
       clients,	 or  it	 can be	specified in the master.cf file	for a specific
       client, for example:

	   /usr/local/etc/postfix/master.cf:
	       mylmtp ... lmtp -o lmtp_lhlo_name=foo.bar.com

       This feature is available in Postfix 2.3	and later.

lmtp_lhlo_timeout (default: 300s)
       The Postfix LMTP	client time limit for sending the  LHLO	 command,  and
       for receiving the initial remote	LMTP server response.

       Time  units:  s (seconds), m (minutes), h (hours), d (days), w (weeks).
       The default time	unit is	s (seconds).

lmtp_line_length_limit (default: 990)
       The LMTP-specific version of the	 smtp_line_length_limit	 configuration
       parameter.  See there for details.

       This feature is available in Postfix 2.3	and later.

lmtp_mail_timeout (default: 300s)
       The  Postfix  LMTP client time limit for	sending	the MAIL FROM command,
       and for receiving the remote LMTP server	response.

       Specify a non-zero time value  (an  integral  value  plus  an  optional
       one-letter  suffix  that	specifies the time unit).  Time	units: s (sec-
       onds), m	(minutes), h (hours), d	(days),	w (weeks).  The	 default  time
       unit is s (seconds).

lmtp_mime_header_checks	(default: empty)
       The  LMTP-specific version of the smtp_mime_header_checks configuration
       parameter. See there for	details.

       This feature is available in Postfix 2.5	and later.

lmtp_min_data_rate (default: 500)
       The LMTP-specific version of the	smtp_min_data_rate  configuration  pa-
       rameter.	See there for details.

       This feature is available in Postfix 3.7	and later.

lmtp_mx_address_limit (default:	5)
       The  LMTP-specific  version  of the smtp_mx_address_limit configuration
       parameter.  See there for details.

       This feature is available in Postfix 2.3	and later.

lmtp_mx_session_limit (default:	2)
       The LMTP-specific version of  the  smtp_mx_session_limit	 configuration
       parameter.  See there for details.

       This feature is available in Postfix 2.3	and later.

lmtp_nested_header_checks (default: empty)
       The  LMTP-specific  version of the smtp_nested_header_checks configura-
       tion parameter. See there for details.

       This feature is available in Postfix 2.5	and later.

lmtp_per_record_deadline (default: no)
       The LMTP-specific version of the	smtp_per_record_deadline configuration
       parameter.  See there for details.

       This feature is available in Postfix 2.9	and later.

lmtp_per_request_deadline (default: no)
       The  LMTP-specific  version of the smtp_per_request_deadline configura-
       tion parameter. See there for details.

       This feature is available in Postfix 3.7	and later.

lmtp_pix_workaround_delay_time (default: 10s)
       The LMTP-specific version of the	smtp_pix_workaround_delay_time config-
       uration parameter.  See there for details.

       This feature is available in Postfix 2.3	and later.

lmtp_pix_workaround_maps (default: empty)
       The LMTP-specific version of the	smtp_pix_workaround_maps configuration
       parameter.  See there for details.

       This feature is available in Postfix 2.4	and later.

lmtp_pix_workaround_threshold_time (default: 500s)
       The LMTP-specific  version  of  the  smtp_pix_workaround_threshold_time
       configuration parameter.	 See there for details.

       This feature is available in Postfix 2.3	and later.

lmtp_pix_workarounds (default: empty)
       The  LMTP-specific version of the smtp_pix_workaround configuration pa-
       rameter.	 See there for details.

       This feature is available in Postfix 2.4	and later.

lmtp_quit_timeout (default: 300s)
       The Postfix LMTP	client time limit for sending the  QUIT	 command,  and
       for receiving the remote	LMTP server response.

       Specify	a  non-zero  time  value  (an  integral	value plus an optional
       one-letter suffix that specifies	the time unit).	 Time units:  s	 (sec-
       onds),  m  (minutes), h (hours),	d (days), w (weeks).  The default time
       unit is s (seconds).

lmtp_quote_rfc821_envelope (default: yes)
       The LMTP-specific version of the	smtp_quote_rfc821_envelope  configura-
       tion parameter.	See there for details.

       This feature is available in Postfix 2.3	and later.

lmtp_randomize_addresses (default: yes)
       The LMTP-specific version of the	smtp_randomize_addresses configuration
       parameter.  See there for details.

       This feature is available in Postfix 2.3	and later.

lmtp_rcpt_timeout (default: 300s)
       The Postfix LMTP	client time limit for sending the RCPT TO command, and
       for receiving the remote	LMTP server response.

       Specify	a  non-zero  time  value  (an  integral	value plus an optional
       one-letter suffix that specifies	the time unit).	 Time units:  s	 (sec-
       onds),  m  (minutes), h (hours),	d (days), w (weeks).  The default time
       unit is s (seconds).

lmtp_reply_filter (default: empty)
       The LMTP-specific version of the	smtp_reply_filter configuration	param-
       eter.  See there	for details.

       This feature is available in Postfix 2.7	and later.

lmtp_rset_timeout (default: 20s)
       The  Postfix  LMTP  client time limit for sending the RSET command, and
       for receiving the remote	LMTP server response. The  LMTP	 client	 sends
       RSET  in	order to finish	a recipient address probe, or to verify	that a
       cached connection is still alive.

       Specify a non-zero time value  (an  integral  value  plus  an  optional
       one-letter  suffix  that	specifies the time unit).  Time	units: s (sec-
       onds), m	(minutes), h (hours), d	(days),	w (weeks).  The	 default  time
       unit is s (seconds).

lmtp_sasl_auth_cache_name (default: empty)
       The  LMTP-specific  version of the smtp_sasl_auth_cache_name configura-
       tion parameter.	See there for details.

       This feature is available in Postfix 2.5	and later.

lmtp_sasl_auth_cache_time (default: 90d)
       The LMTP-specific version of the	 smtp_sasl_auth_cache_time  configura-
       tion parameter.	See there for details.

       This feature is available in Postfix 2.5	and later.

lmtp_sasl_auth_enable (default:	no)
       Enable SASL authentication in the Postfix LMTP client.

lmtp_sasl_auth_soft_bounce (default: yes)
       The  LMTP-specific version of the smtp_sasl_auth_soft_bounce configura-
       tion parameter.	See there for details.

       This feature is available in Postfix 2.5	and later.

lmtp_sasl_mechanism_filter (default: empty)
       The LMTP-specific version of the	smtp_sasl_mechanism_filter  configura-
       tion parameter.	See there for details.

       This feature is available in Postfix 2.3	and later.

lmtp_sasl_password_maps	(default: empty)
       Optional	 Postfix  LMTP client lookup tables with one username:password
       entry per host or domain.  If a remote host  or	domain	has  no	 user-
       name:password  entry,  then the Postfix LMTP client will	not attempt to
       authenticate to the remote host.

lmtp_sasl_path (default: empty)
       Implementation-specific information that	is passed through to the  SASL
       plug-in implementation that is selected with lmtp_sasl_type.  Typically
       this specifies the name of a configuration file or rendezvous point.

       This feature is available in Postfix 2.3	and later.

lmtp_sasl_security_options (default: noplaintext, noanonymous)
       SASL security options; as of Postfix 2.3	the list of available features
       depends	on  the	 SASL  client  implementation  that  is	 selected with
       lmtp_sasl_type.

       The following security features are defined for the cyrus  client  SASL
       implementation:

       noplaintext
	      Disallow authentication methods that use plaintext passwords.

       noactive
	      Disallow	authentication methods that are	vulnerable to non-dic-
	      tionary active attacks.

       nodictionary
	      Disallow authentication methods that are vulnerable  to  passive
	      dictionary attacks.

       noanonymous
	      Disallow anonymous logins.

       Example:

       lmtp_sasl_security_options = noplaintext

lmtp_sasl_tls_security_options (default: $lmtp_sasl_security_options)
       The LMTP-specific version of the	smtp_sasl_tls_security_options config-
       uration parameter.  See there for details.

       This feature is available in Postfix 2.3	and later.

lmtp_sasl_tls_verified_security_options	(default:  $lmtp_sasl_tls_security_op-
       tions)
       The  LMTP-specific  version  of the smtp_sasl_tls_verified_security_op-
       tions configuration parameter.  See there for details.

       This feature is available in Postfix 2.3	and later.

lmtp_sasl_type (default: cyrus)
       The SASL	plug-in	type that the Postfix LMTP client should use  for  au-
       thentication.   The  available  types are listed	with the "postconf -A"
       command.

       This feature is available in Postfix 2.3	and later.

lmtp_send_dummy_mail_auth (default: no)
       The LMTP-specific version of the	 smtp_send_dummy_mail_auth  configura-
       tion parameter.	See there for details.

       This feature is available in Postfix 2.9	and later.

lmtp_send_xforward_command (default: no)
       Send  an	 XFORWARD command to the remote	LMTP server when the LMTP LHLO
       server response announces XFORWARD support.  This allows	an lmtp(8) de-
       livery agent, used for content filter message injection,	to forward the
       name, address, protocol and HELO	name of	the  original  client  to  the
       content filter and downstream LMTP server.  Before you change the value
       to yes, it is best to make sure that your content filter	supports  this
       command.

       This feature is available in Postfix 2.1	and later.

lmtp_sender_dependent_authentication (default: no)
       The  LMTP-specific  version of the smtp_sender_dependent_authentication
       configuration parameter.	 See there for details.

       This feature is available in Postfix 2.3	and later.

lmtp_skip_5xx_greeting (default: yes)
       The LMTP-specific version of the	 smtp_skip_5xx_greeting	 configuration
       parameter.  See there for details.

       This feature is available in Postfix 2.3	and later.

lmtp_skip_quit_response	(default: no)
       Wait for	the response to	the LMTP QUIT command.

lmtp_starttls_timeout (default:	300s)
       The  LMTP-specific  version  of the smtp_starttls_timeout configuration
       parameter.  See there for details.

       This feature is available in Postfix 2.3	and later.

lmtp_tcp_port (default:	24)
       The default TCP port that the Postfix LMTP client connects to.  Specify
       a symbolic name (see services(5)) or a numeric port.

lmtp_tls_CAfile	(default: empty)
       The  LMTP-specific version of the smtp_tls_CAfile configuration parame-
       ter.  See there for details.

       This feature is available in Postfix 2.3	and later.

lmtp_tls_CApath	(default: empty)
       The LMTP-specific version of the	smtp_tls_CApath	configuration  parame-
       ter.  See there for details.

       This feature is available in Postfix 2.3	and later.

lmtp_tls_block_early_mail_reply	(default: empty)
       The  LMTP-specific  version of the smtp_tls_block_early_mail_reply con-
       figuration parameter.  See there	for details.

       This feature is available in Postfix 2.7	and later.

lmtp_tls_cert_file (default: empty)
       The LMTP-specific version of the	smtp_tls_cert_file  configuration  pa-
       rameter.	 See there for details.

       This feature is available in Postfix 2.3	and later.

lmtp_tls_chain_files (default: empty)
       The LMTP-specific version of the	smtp_tls_chain_files configuration pa-
       rameter.	See there for details.

       This feature is available in Postfix 3.4	and later.

lmtp_tls_ciphers (default: medium)
       The LMTP-specific version of the	smtp_tls_ciphers configuration parame-
       ter. See	there for details.

       This feature is available in Postfix 2.6	and later.

lmtp_tls_connection_reuse (default: no)
       The  LMTP-specific  version of the smtp_tls_connection_reuse configura-
       tion parameter. See there for details.

       This feature is available in Postfix 3.4	and later.

lmtp_tls_dcert_file (default: empty)
       The LMTP-specific version of the	smtp_tls_dcert_file configuration  pa-
       rameter.	 See there for details.

       This feature is available in Postfix 2.3	and later.

lmtp_tls_dkey_file (default: $lmtp_tls_dcert_file)
       The  LMTP-specific  version of the smtp_tls_dkey_file configuration pa-
       rameter.	 See there for details.

       This feature is available in Postfix 2.3	and later.

lmtp_tls_eccert_file (default: empty)
       The LMTP-specific version of the	smtp_tls_eccert_file configuration pa-
       rameter.	 See there for details.

       This  feature  is  available  in	Postfix	2.6 and	later, when Postfix is
       compiled	and linked with	OpenSSL	1.0.0 or later.

lmtp_tls_eckey_file (default: empty)
       The LMTP-specific version of the	smtp_tls_eckey_file configuration  pa-
       rameter.	 See there for details.

       This  feature  is  available  in	Postfix	2.6 and	later, when Postfix is
       compiled	and linked with	OpenSSL	1.0.0 or later.

lmtp_tls_enforce_peername (default: yes)
       The LMTP-specific version of the	 smtp_tls_enforce_peername  configura-
       tion parameter.	See there for details.

       This feature is available in Postfix 2.3	and later.

lmtp_tls_exclude_ciphers (default: empty)
       The LMTP-specific version of the	smtp_tls_exclude_ciphers configuration
       parameter.  See there for details.

       This feature is available in Postfix 2.3	and later.

lmtp_tls_fingerprint_cert_match	(default: empty)
       The LMTP-specific version of the	 smtp_tls_fingerprint_cert_match  con-
       figuration parameter.  See there	for details.

       This feature is available in Postfix 2.5	and later.

lmtp_tls_fingerprint_digest (default: see postconf -d output)
       The LMTP-specific version of the	smtp_tls_fingerprint_digest configura-
       tion parameter.	See there for details.

       This feature is available in Postfix 2.5	and later.

lmtp_tls_force_insecure_host_tlsa_lookup (default: no)
       The    LMTP-specific    version	   of	  the	  smtp_tls_force_inse-
       cure_host_tlsa_lookup configuration parameter.  See there for details.

       This feature is available in Postfix 2.11 and later.

lmtp_tls_key_file (default: $lmtp_tls_cert_file)
       The LMTP-specific version of the	smtp_tls_key_file configuration	param-
       eter.  See there	for details.

       This feature is available in Postfix 2.3	and later.

lmtp_tls_loglevel (default: 0)
       The LMTP-specific version of the	smtp_tls_loglevel configuration	param-
       eter.  See there	for details.

       This feature is available in Postfix 2.3	and later.

lmtp_tls_mandatory_ciphers (default: medium)
       The  LMTP-specific version of the smtp_tls_mandatory_ciphers configura-
       tion parameter.	See there for details.

       This feature is available in Postfix 2.3	and later.

lmtp_tls_mandatory_exclude_ciphers (default: empty)
       The LMTP-specific  version  of  the  smtp_tls_mandatory_exclude_ciphers
       configuration parameter.	 See there for details.

       This feature is available in Postfix 2.3	and later.

lmtp_tls_mandatory_protocols (default: see postconf -d output)
       The  LMTP-specific version of the smtp_tls_mandatory_protocols configu-
       ration parameter. See there for details.

       This feature is available in Postfix 2.3	and later.

lmtp_tls_note_starttls_offer (default: no)
       The LMTP-specific version of the	smtp_tls_note_starttls_offer  configu-
       ration parameter.  See there for	details.

       This feature is available in Postfix 2.3	and later.

lmtp_tls_per_site (default: empty)
       The LMTP-specific version of the	smtp_tls_per_site configuration	param-
       eter.  See there	for details.

       This feature is available in Postfix 2.3	and later.

lmtp_tls_policy_maps (default: empty)
       The LMTP-specific version of the	smtp_tls_policy_maps configuration pa-
       rameter.	See there for details.

       This feature is available in Postfix 2.3	and later.

lmtp_tls_protocols (default: see postconf -d output)
       The  LMTP-specific  version of the smtp_tls_protocols configuration pa-
       rameter.	See there for details.

       This feature is available in Postfix 2.6	and later.

lmtp_tls_scert_verifydepth (default: 9)
       The LMTP-specific version of the	smtp_tls_scert_verifydepth  configura-
       tion parameter.	See there for details.

       This feature is available in Postfix 2.3	and later.

lmtp_tls_secure_cert_match (default: nexthop)
       The  LMTP-specific version of the smtp_tls_secure_cert_match configura-
       tion parameter. See there for details.

       This feature is available in Postfix 2.3	and later.

lmtp_tls_security_level	(default: empty)
       The LMTP-specific version of the	smtp_tls_security_level	 configuration
       parameter.  See there for details.

       This feature is available in Postfix 2.3	and later.

lmtp_tls_servername (default: empty)
       The  LMTP-specific version of the smtp_tls_servername configuration pa-
       rameter.	See there for details.

       This feature is available in Postfix 3.4	and later.

lmtp_tls_session_cache_database	(default: empty)
       The LMTP-specific version of the	 smtp_tls_session_cache_database  con-
       figuration parameter. See there for details.

       This feature is available in Postfix 2.3	and later.

lmtp_tls_session_cache_timeout (default: 3600s)
       The LMTP-specific version of the	smtp_tls_session_cache_timeout config-
       uration parameter.  See there for details.

       This feature is available in Postfix 2.3	and later.

lmtp_tls_trust_anchor_file (default: empty)
       The LMTP-specific version of the	smtp_tls_trust_anchor_file  configura-
       tion parameter.	See there for details.

       This feature is available in Postfix 2.11 and later.

lmtp_tls_verify_cert_match (default: hostname)
       The  LMTP-specific version of the smtp_tls_verify_cert_match configura-
       tion parameter. See there for details.

       This feature is available in Postfix 2.3	and later.

lmtp_tls_wrappermode (default: no)
       The LMTP-specific version of the	smtp_tls_wrappermode configuration pa-
       rameter.	See there for details.

       This feature is available in Postfix 3.0	and later.

lmtp_use_tls (default: no)
       The  LMTP-specific version of the smtp_use_tls configuration parameter.
       See there for details.

       This feature is available in Postfix 2.3	and later.

lmtp_xforward_timeout (default:	300s)
       The Postfix LMTP	client time limit for sending  the  XFORWARD  command,
       and for receiving the remote LMTP server	response.

       In  case	 of  problems  the client does NOT try the next	address	on the
       mail exchanger list.

       Specify a non-zero time value  (an  integral  value  plus  an  optional
       one-letter  suffix  that	specifies the time unit).  Time	units: s (sec-
       onds), m	(minutes), h (hours), d	(days),	w (weeks).  The	 default  time
       unit is s (seconds).

       This feature is available in Postfix 2.1	and later.

local_command_shell (default: empty)
       Optional	 shell	program	for local(8) delivery to non-Postfix commands.
       By default, non-Postfix commands	are executed  directly;	 commands  are
       given  to the default shell (typically, /bin/sh)	only when they contain
       shell meta characters or	shell built-in commands.

       "sendmail's restricted shell" (smrsh) is	what most people will  use  in
       order  to  restrict  what  programs can be run from e.g.	.forward files
       (smrsh is part of the Sendmail distribution).

       Note: when a shell program is specified,	it is invoked  even  when  the
       command contains	no shell built-in commands or meta characters.

       Example:

       local_command_shell = /some/where/smrsh -c
       local_command_shell = /bin/bash -c

local_delivery_status_filter (default: $default_delivery_status_filter)
       Optional	 filter	 for  the local(8) delivery agent to change the	status
       code or explanatory text	of successful or unsuccessful deliveries.  See
       default_delivery_status_filter for details.

       This feature is available in Postfix 3.0	and later.

local_destination_concurrency_limit (default: 2)
       The  maximal  number of parallel	deliveries via the local mail delivery
       transport  to  the  same	 recipient  (when   "local_destination_recipi-
       ent_limit  =  1")  or  the maximal number of parallel deliveries	to the
       same local domain (when "local_destination_recipient_limit > 1").  This
       limit  is enforced by the queue manager.	The message delivery transport
       name is the first field in the entry in the master.cf file.

       A low limit of 2	is recommended,	just in	case someone has an  expensive
       shell  command  in a .forward file or in	an alias (e.g.,	a mailing list
       manager).  You don't want to run	lots of	those at the same time.

local_destination_recipient_limit (default: 1)
       The maximal number of recipients	per message  delivery  via  the	 local
       mail  delivery  transport. This limit is	enforced by the	queue manager.
       The message delivery transport name is the first	field in the entry  in
       the master.cf file.

       Setting this parameter to a value > 1 changes the meaning of local_des-
       tination_concurrency_limit from concurrency per recipient into  concur-
       rency per domain.

local_header_rewrite_clients (default: permit_inet_interfaces)
       Rewrite	message	header addresses in mail from these clients and	update
       incomplete addresses with the domain name in  $myorigin	or  $mydomain;
       either  don't rewrite message headers from other	clients	at all,	or re-
       write message headers and update	incomplete addresses with  the	domain
       specified in the	remote_header_rewrite_domain parameter.

       See  the	 append_at_myorigin and	append_dot_mydomain parameters for de-
       tails of	how domain names are appended to incomplete addresses.

       Specify a list of zero or more of the following:

       permit_inet_interfaces
	      Append the domain	name in	$myorigin or $mydomain when the	client
	      IP address matches $inet_interfaces. This	is enabled by default.

       permit_mynetworks
	      Append the domain	name in	$myorigin or $mydomain when the	client
	      IP address matches any network  or  network  address  listed  in
	      $mynetworks.  This  setting  will	not prevent remote mail	header
	      address rewriting	when mail from a remote	client is forwarded by
	      a	neighboring system.

       permit_sasl_authenticated
	      Append the domain	name in	$myorigin or $mydomain when the	client
	      is successfully authenticated via	the RFC	4954 (AUTH) protocol.

       permit_tls_clientcerts
	      Append the domain	name in	$myorigin or $mydomain when the	remote
	      SMTP  client  TLS	 certificate fingerprint or public key finger-
	      print (Postfix 2.9 and later) is listed  in  $relay_clientcerts.
	      The   fingerprint	 digest	 algorithm  is	configurable  via  the
	      smtpd_tls_fingerprint_digest parameter (hard-coded as md5	 prior
	      to Postfix version 2.5).
	      The default algorithm is sha256 with Postfix >= 3.6 and the com-
	      patibility_level set to 3.6 or higher. With Postfix <= 3.5,  the
	      default  algorithm  is  md5.  The	best-practice algorithm	is now
	      sha256. Recent advances in hash function cryptanalysis have  led
	      to  md5  and sha1	being deprecated in favor of sha256.  However,
	      as long as there are no known "second pre-image" attacks against
	      the older	algorithms, their use in this context, though not rec-
	      ommended,	is still likely	safe.

       permit_tls_all_clientcerts
	      Append the domain	name in	$myorigin or $mydomain when the	remote
	      SMTP client TLS certificate is successfully verified, regardless
	      of whether it is listed on the server,  and  regardless  of  the
	      certifying authority.

       check_address_map type:table

       type:table
	      Append the domain	name in	$myorigin or $mydomain when the	client
	      IP address matches the specified lookup table.  The  lookup  re-
	      sult  is ignored,	and no subnet lookup is	done. This is suitable
	      for, e.g., pop-before-smtp lookup	tables.

       Examples:

       The Postfix < 2.2 backwards compatible setting: always rewrite  message
       headers,	 and  always  append  my  own  domain to incomplete header ad-
       dresses.

	   local_header_rewrite_clients	= static:all

       The purist (and default)	setting: rewrite headers  only	in  mail  from
       Postfix sendmail	and in SMTP mail from this machine.

	   local_header_rewrite_clients	= permit_inet_interfaces

       The intermediate	setting: rewrite header	addresses and append $myorigin
       or $mydomain information	only with mail from Postfix sendmail, from lo-
       cal clients, or from authorized SMTP clients.

       Note:  this setting will	not prevent remote mail	header address rewrit-
       ing when	mail from a remote client is forwarded by a  neighboring  sys-
       tem.

	   local_header_rewrite_clients	= permit_mynetworks,
	       permit_sasl_authenticated permit_tls_clientcerts
	       check_address_map hash:$config_directory/pop-before-smtp

local_login_sender_maps	(default: static:*)
       A  list	of lookup tables that are searched by the UNIX login name, and
       that return a list of allowed envelope  sender  patterns	 separated  by
       space or	comma. These sender patterns are enforced by the Postfix post-
       drop(1) command.	The default is backwards-compatible:  every  user  may
       specify any sender envelope address.

       When  no	 UNIX  login  name  is available, the postdrop(1) command will
       prepend "uid:" to the numerical UID and use that	instead.

       This feature ignores address extensions in the user-specified  envelope
       sender address.

       The following sender patterns are special; these	cannot be used as part
       of a longer pattern.

	*     This pattern allows any envelope sender address.

	<>    This pattern allows the empty envelope sender address.  See  the
	      empty_address_local_login_sender_maps_lookup_key	 configuration
	      parameter.

	@domain
	      This pattern allows an envelope sender address when the '@'  and
	      domain part match.

       Examples:

       /usr/local/etc/postfix/main.cf:
	   # Allow root	and postfix full control, anyone else can only
	   # send mail as themselves. Use "uid:" followed by the numerical
	   # UID when the UID has no entry in the UNIX password	file.
	   local_login_sender_maps =
	       inline:{	{ root = * }, {	postfix	= * } },
	       pcre:$config_directory/login_senders

       /usr/local/etc/postfix/login_senders:
	  # Allow both the bare	username and the user@domain forms.
	   /(.+)/ $1 $1@example.com

       This feature is available in Postfix 3.6	and later.

local_recipient_maps (default: proxy:unix:passwd.byname	$alias_maps)
       Lookup tables with all names or addresses of local recipients: a	recip-
       ient address is local when its domain matches $mydestination, $inet_in-
       terfaces	 or $proxy_interfaces.	Specify	@domain	as a wild-card for do-
       mains that do not have a	valid  recipient  list.	  Technically,	tables
       listed  with  $local_recipient_maps are used as lists: Postfix needs to
       know only if a lookup string is found or	not, but it does not  use  the
       result from table lookup.

       Specify zero or more "type:name"	lookup tables, separated by whitespace
       or comma. Tables	will be	searched in the	specified order	until a	 match
       is found.

       If  this	 parameter  is	non-empty (the default), then the Postfix SMTP
       server will reject mail for unknown local users.

       To turn off local recipient checking in the Postfix SMTP	server,	 spec-
       ify "local_recipient_maps =" (i.e. empty).

       The  default setting assumes that you use the default Postfix local de-
       livery agent for	local delivery.	You need to update  the	 local_recipi-
       ent_maps	setting	if:

       o      You redefine the local delivery agent in master.cf.

       o      You redefine the "local_transport" setting in main.cf.

       o      You   use	 the  "luser_relay",  "mailbox_transport",  or	"fall-
	      back_transport" feature of the Postfix local(8) delivery agent.

       Details are described in	the LOCAL_RECIPIENT_README file.

       Beware: if the Postfix SMTP server runs chrooted, you  need  to	access
       the  passwd  file via the proxymap(8) service, in order to overcome ch-
       root access restrictions. The alternative, maintaining a	 copy  of  the
       system password file in the chroot jail is not practical.

       Examples:

       local_recipient_maps =

local_transport	(default: local:$myhostname)
       The  default mail delivery transport and	next-hop destination for final
       delivery	to domains listed with mydestination, and for [ipaddress] des-
       tinations  that	match $inet_interfaces or $proxy_interfaces.  This in-
       formation can be	overruled with the transport(5)	table.

       By default, local mail is delivered to the  transport  called  "local",
       which is	just the name of a service that	is defined the master.cf file.

       Specify	a string of the	form transport:nexthop,	where transport	is the
       name of a mail delivery transport defined in master.cf.	 The  :nexthop
       destination is optional;	its syntax is documented in the	manual page of
       the corresponding delivery agent.

       Beware: if you override the default local delivery agent	then you  need
       to  review  the	LOCAL_RECIPIENT_README	document,  otherwise  the SMTP
       server may reject mail for local	recipients.

luser_relay (default: empty)
       Optional	catch-all destination for unknown local(8) recipients.	By de-
       fault,  mail  for  unknown recipients in	domains	that match $mydestina-
       tion, $inet_interfaces or $proxy_interfaces is returned	as  undeliver-
       able.

       The luser_relay value is	not subject to Postfix configuration parameter
       $name expansion.	Instead, the following $name expansions	are done:

       $domain
	      The recipient domain.

       $extension
	      The recipient address extension.

       $home  The recipient's home directory.

       $local The entire recipient address localpart.

       $recipient
	      The full recipient address.

       $recipient_delimiter
	      The address extension delimiter that was found in	the  recipient
	      address  (Postfix	 2.11 and later), or the system-wide recipient
	      address extension	delimiter (Postfix 2.10	and earlier).

       $shell The recipient's login shell.

       $user  The recipient username.

       ${name?value}

       ${name?{value}} (Postfix	>= 3.0)
	      Expands to value when $name is non-empty.

       ${name:value}

       ${name:{value}} (Postfix	>= 3.0)
	      Expands to value when $name is empty.

       ${name?{value1}:{value2}} (Postfix >= 3.0)
	      Expands to value1	when $name is non-empty, value2	otherwise.

       Instead of $name	you can	also specify ${name} or	$(name).

       Note: luser_relay works only for	the Postfix local(8) delivery agent.

       Note: if	you use	this feature for accounts not  in  the	UNIX  password
       file,  then  you	 must specify "local_recipient_maps =" (i.e. empty) in
       the main.cf file, otherwise the Postfix SMTP server  will  reject  mail
       for non-UNIX accounts with "User	unknown	in local recipient table".

       Examples:

       luser_relay = $user@other.host
       luser_relay = $local@other.host
       luser_relay = admin+$local

mail_name (default: Postfix)
       The  mail  system  name	that is	displayed in Received: headers,	in the
       SMTP greeting banner, and in bounced mail.

mail_owner (default: postfix)
       The UNIX	system account that owns the Postfix queue  and	 most  Postfix
       daemon  processes.   Specify  the  name of an unprivileged user account
       that does not share a user or group ID with other  accounts,  and  that
       owns  no	 other files or	processes on the system.  In particular, don't
       specify nobody or daemon.  PLEASE USE A DEDICATED USER ID AND GROUP ID.

       When this parameter value  is  changed  you  need  to  re-run  "postfix
       set-permissions"	 (with	Postfix	 version  2.0  and  earlier: "/usr/lo-
       cal/etc/postfix/post-install set-permissions".

mail_release_date (default: see	postconf -d output)
       The Postfix release date, in "YYYYMMDD" format.

mail_spool_directory (default: see postconf -d output)
       The directory where local(8) UNIX-style mailboxes are kept. The default
       setting	depends	 on  the  system  type.	Specify	a name ending in / for
       maildir-style delivery.

       Note: maildir delivery is done with the privileges  of  the  recipient.
       If you use the mail_spool_directory setting for maildir style delivery,
       then you	must create the	top-level maildir directory in advance.	 Post-
       fix will	not create it.

       Examples:

       mail_spool_directory = /var/mail
       mail_spool_directory = /var/spool/mail

mail_version (default: see postconf -d output)
       The  version  of	 the  mail system. Stable releases are named major.mi-
       nor.patchlevel. Experimental releases also include  the	release	 date.
       The  version string can be used in, for example,	the SMTP greeting ban-
       ner.

mailbox_command	(default: empty)
       Optional	external command that the local(8) delivery agent  should  use
       for mailbox delivery.  The command is run with the user ID and the pri-
       mary group ID privileges	of the recipient.  Exception: command delivery
       for  root executes with $default_privs privileges.  This	is not a prob-
       lem, because 1) mail for	root should always be aliased to a  real  user
       and 2) don't log	in as root, use	"su" instead.

       The following environment variables are exported	to the command:

       CLIENT_ADDRESS
	      Remote  client network address. Available	in Postfix version 2.2
	      and later.

       CLIENT_HELO
	      Remote client EHLO command parameter. Available in Postfix  ver-
	      sion 2.2 and later.

       CLIENT_HOSTNAME
	      Remote  client  hostname.	 Available  in Postfix version 2.2 and
	      later.

       CLIENT_PROTOCOL
	      Remote client protocol. Available	in  Postfix  version  2.2  and
	      later.

       DOMAIN The domain part of the recipient address.

       EXTENSION
	      The optional address extension.

       HOME   The recipient home directory.

       LOCAL  The recipient address localpart.

       LOGNAME
	      The recipient's username.

       ORIGINAL_RECIPIENT
	      The  entire  recipient  address, before any address rewriting or
	      aliasing.

       RECIPIENT
	      The full recipient address.

       SASL_METHOD
	      SASL authentication method specified in the remote  client  AUTH
	      command. Available in Postfix version 2.2	and later.

       SASL_SENDER
	      SASL  sender  address  specified	in the remote client MAIL FROM
	      command. Available in Postfix version 2.2	and later.

       SASL_USER
	      SASL username specified  in  the	remote	client	AUTH  command.
	      Available	in Postfix version 2.2 and later.

       SENDER The full sender address.

       SHELL  The recipient's login shell.

       USER   The recipient username.

       Unlike  other Postfix configuration parameters, the mailbox_command pa-
       rameter is not subjected	to $name substitutions.	This  is  to  make  it
       easier to specify shell syntax (see example below).

       If you can, avoid shell meta characters because they will force Postfix
       to run an expensive shell process. If you're delivering via  "procmail"
       then  running  a	 shell won't make a noticeable difference in the total
       cost.

       Note: if	you use	the  mailbox_command  feature  to  deliver  mail  sys-
       tem-wide,  you  must  set  up an	alias that forwards mail for root to a
       real user.

       The precedence of local(8) delivery  features  from  high  to  low  is:
       aliases,	 .forward  files,  mailbox_transport_maps,  mailbox_transport,
       mailbox_command_maps, mailbox_command, home_mailbox,  mail_spool_direc-
       tory, fallback_transport_maps, fallback_transport and luser_relay.

       Examples:

       mailbox_command = /some/where/procmail
       mailbox_command = /some/where/procmail -a "$EXTENSION"
       mailbox_command = /some/where/maildrop -d "$USER"
	       -f "$SENDER" "$EXTENSION"

mailbox_command_maps (default: empty)
       Optional	 lookup	tables with per-recipient external commands to use for
       local(8)	mailbox	delivery.  Behavior is as with mailbox_command.

       The precedence of local(8) delivery  features  from  high  to  low  is:
       aliases,	 .forward  files,  mailbox_transport_maps,  mailbox_transport,
       mailbox_command_maps, mailbox_command, home_mailbox,  mail_spool_direc-
       tory, fallback_transport_maps, fallback_transport and luser_relay.

       Specify zero or more "type:name"	lookup tables, separated by whitespace
       or comma. Tables	will be	searched in the	specified order	until a	 match
       is found.

mailbox_delivery_lock (default:	see postconf -d	output)
       How  to	lock a UNIX-style local(8) mailbox before attempting delivery.
       For a list of available file locking methods,  use  the	"postconf  -l"
       command.

       This  setting  is ignored with maildir style delivery, because such de-
       liveries	are safe without explicit locks.

       Note: The dotlock method	requires that the recipient  UID  or  GID  has
       write access to the parent directory of the mailbox file.

       Note: the default setting of this parameter is system dependent.

mailbox_size_limit (default: 51200000)
       The maximal size	of any local(8)	individual mailbox or maildir file, or
       zero (no	limit).	 In fact, this limits the size of  any	file  that  is
       written	to  upon  local	 delivery, including files written by external
       commands	that are executed by the local(8) delivery  agent.  The	 value
       cannot exceed LONG_MAX (typically, a 32-bit or 64-bit signed integer).

       This limit must not be smaller than the message size limit.

mailbox_transport (default: empty)
       Optional	 message  delivery  transport that the local(8)	delivery agent
       should use for mailbox delivery to all local recipients,	whether	or not
       they are	found in the UNIX passwd database.

       The  precedence	of  local(8)  delivery	features  from high to low is:
       aliases,	 .forward  files,  mailbox_transport_maps,  mailbox_transport,
       mailbox_command_maps,  mailbox_command, home_mailbox, mail_spool_direc-
       tory, fallback_transport_maps, fallback_transport and luser_relay.

mailbox_transport_maps (default: empty)
       Optional	lookup tables with per-recipient message  delivery  transports
       to use for local(8) mailbox delivery, whether or	not the	recipients are
       found in	the UNIX passwd	database.

       The precedence of local(8) delivery  features  from  high  to  low  is:
       aliases,	 .forward  files,  mailbox_transport_maps,  mailbox_transport,
       mailbox_command_maps, mailbox_command, home_mailbox,  mail_spool_direc-
       tory, fallback_transport_maps, fallback_transport and luser_relay.

       Specify zero or more "type:name"	lookup tables, separated by whitespace
       or comma. Tables	will be	searched in the	specified order	until a	 match
       is found.

       For  safety  reasons, this feature does not allow $number substitutions
       in regular expression maps.

       This feature is available in Postfix 2.3	and later.

maillog_file (default: empty)
       The name	of an optional logfile that is written by  the	Postfix	 post-
       logd(8) service.	An empty value selects logging to syslogd(8).  Specify
       "/dev/stdout" to	select logging to standard output. Stdout logging  re-
       quires that Postfix is started with "postfix start-fg".

       Note  1:	The maillog_file parameter value must contain a	prefix that is
       specified with the maillog_file_prefixes	parameter.

       Note 2: Some Postfix non-daemon programs	may still log  information  to
       syslogd(8),  before  they have processed	their configuration parameters
       and command-line	options.

       This feature is available in Postfix 3.4	and later.

maillog_file_compressor	(default: gzip)
       The program to run after	rotating $maillog_file	with  "postfix	logro-
       tate".  The  command  is	run with the rotated logfile name as its first
       argument.

       This feature is available in Postfix 3.4	and later.

maillog_file_prefixes (default:	/var, /dev/stdout)
       A list of allowed prefixes for a	maillog_file value. This is  a	safety
       feature	to  contain  the  damage  from a single	configuration mistake.
       Specify one or more prefix strings, separated by	comma or whitespace.

       This feature is available in Postfix 3.4	and later.

maillog_file_rotate_suffix (default: %Y%m%d-%H%M%S)
       The format of the suffix	to append to $maillog_file while rotating  the
       file  with "postfix logrotate". See strftime(3) for syntax. The default
       suffix, YYYYMMDD-HHMMSS,	allows logs to be rotated frequently.

       This feature is available in Postfix 3.4	and later.

mailq_path (default: see postconf -d output)
       Sendmail	 compatibility	feature	 that  specifies  where	 the   Postfix
       mailq(1)	 command  is  installed.  This command can be used to list the
       Postfix mail queue.

manpage_directory (default: see	postconf -d output)
       Where the Postfix manual	pages are installed.

maps_rbl_domains (default: empty)
       Obsolete	feature: use the reject_rbl_client feature instead.

maps_rbl_reject_code (default: 554)
       The numerical Postfix SMTP server response  code	 when  a  remote  SMTP
       client	 request    is	 blocked   by	the   reject_rbl_client,   re-
       ject_rhsbl_client, reject_rhsbl_reverse_client, reject_rhsbl_sender  or
       reject_rhsbl_recipient restriction.

       Do  not	change	this  unless  you have a complete understanding	of RFC
       5321.

masquerade_classes (default: envelope_sender, header_sender, header_recipient)

       What addresses are subject to address masquerading.

       By  default,  address  masquerading  is	limited	to envelope sender ad-
       dresses,	and to header sender and header	recipient addresses.  This al-
       lows  you to use	address	masquerading on	a mail gateway while still be-
       ing able	to forward mail	to users on individual machines.

       Specify	zero  or   more	  of:	envelope_sender,   envelope_recipient,
       header_sender, header_recipient

masquerade_domains (default: empty)
       Optional	list of	domains	whose subdomain	structure will be stripped off
       in email	addresses.

       The list	is processed left to right, and	processing stops at the	 first
       match.  Thus,

	   masquerade_domains =	foo.example.com	example.com

       strips  "user@any.thing.foo.example.com"	to "user@foo.example.com", but
       strips "user@any.thing.else.example.com"	to "user@example.com".

       A domain	name prefixed with ! means do not masquerade  this  domain  or
       its subdomains. Thus,

	   masquerade_domains =	!foo.example.com example.com

       does  not  change  "user@any.thing.foo.example.com"  or "user@foo.exam-
       ple.com", but strips "user@any.thing.else.example.com"  to  "user@exam-
       ple.com".

       Note:  with  Postfix  version  2.2, message header address masquerading
       happens only when message header	address	rewriting is enabled:

       o      The message is received with the Postfix sendmail(1) command,

       o      The message is received from a network client that matches  $lo-
	      cal_header_rewrite_clients,

       o      The   message   is  received  from  the  network,	 and  the  re-
	      mote_header_rewrite_domain  parameter  specifies	 a   non-empty
	      value.

       To   get	  the  behavior	 before	 Postfix  version  2.2,	 specify  "lo-
       cal_header_rewrite_clients = static:all".

       Example:

       masquerade_domains = $mydomain

masquerade_exceptions (default:	empty)
       Optional	list of	user names that	are  not  subjected  to	 address  mas-
       querading, even when their addresses match $masquerade_domains.

       By default, address masquerading	makes no exceptions.

       Specify	a  list	 of user names,	"/file/name" or	"type:table" patterns,
       separated by commas and/or whitespace. The  list	 is  matched  left  to
       right,  and the search stops on the first match.	A "/file/name" pattern
       is replaced by its contents; a "type:table"  lookup  table  is  matched
       when  a name matches a lookup key (the lookup result is ignored).  Con-
       tinue long lines	by starting the	next  line  with  whitespace.  Specify
       "!pattern"  to  exclude a name from the list. The form "!/file/name" is
       supported only in Postfix version 2.4 and later.

       Examples:

       masquerade_exceptions = root, mailer-daemon
       masquerade_exceptions = root

master_service_disable (default: empty)
       Selectively disable master(8) listener ports by service type or by ser-
       vice  name  and type.  Specify a	list of	service	types ("inet", "unix",
       "fifo", or "pass") or "name/type" tuples, where	"name"	is  the	 first
       field  of a master.cf entry and "type" is a service type. As with other
       Postfix matchlists, a search stops at the first match.  Specify	"!pat-
       tern"  to  exclude  a  service from the list. By	default, all master(8)
       listener	ports are enabled.

       Note: this feature does not support "/file/name"	or  "type:table"  pat-
       terns,  nor does	it support wildcards such as "*" or "all". This	is in-
       tentional.

       Examples:

       # With Postfix 2.6..2.10	use '.'	instead	of '/'.
       # Turn on all master(8) listener	ports (the default).
       master_service_disable =
       # Turn off only the main	SMTP listener port.
       master_service_disable =	smtp/inet
       # Turn off all TCP/IP listener ports.
       master_service_disable =	inet
       # Turn off all TCP/IP listener ports except "foo".
       master_service_disable =	!foo/inet, inet

       This feature is available in Postfix 2.6	and later.

max_idle (default: 100s)
       The maximum amount of time that an idle Postfix	daemon	process	 waits
       for an incoming connection before terminating voluntarily.  This	param-
       eter is ignored by the Postfix queue manager and	 by  other  long-lived
       Postfix daemon processes.

       Specify	a  non-zero  time  value  (an  integral	value plus an optional
       one-letter suffix that specifies	the time unit).	 Time units:  s	 (sec-
       onds),  m  (minutes), h (hours),	d (days), w (weeks).  The default time
       unit is s (seconds).

max_use	(default: 100)
       The maximal number  of  incoming	 connections  that  a  Postfix	daemon
       process will service before terminating voluntarily.  This parameter is
       ignored by the Postfix queue manager and	by  other  long-lived  Postfix
       daemon processes.

maximal_backoff_time (default: 4000s)
       The maximal time	between	attempts to deliver a deferred message.

       This parameter should be	set to a value greater than or equal to	$mini-
       mal_backoff_time. See also $queue_run_delay.

       Specify a non-zero time value  (an  integral  value  plus  an  optional
       one-letter  suffix  that	specifies the time unit).  Time	units: s (sec-
       onds), m	(minutes), h (hours), d	(days),	w (weeks).  The	 default  time
       unit is s (seconds).

maximal_queue_lifetime (default: 5d)
       Consider	 a message as undeliverable, when delivery fails with a	tempo-
       rary  error,  and  the  time  in	 the  queue  has  reached  the	 maxi-
       mal_queue_lifetime limit.

       Specify	a  non-negative	time value (an integral	value plus an optional
       one-letter suffix that specifies	the time unit).	 Time units:  s	 (sec-
       onds),  m  (minutes), h (hours),	d (days), w (weeks).  The default time
       unit is d (days).

       Specify 0 when mail delivery should be tried only once.

message_drop_headers (default: bcc, content-length, resent-bcc,	return-path)
       Names of	message	headers	that the cleanup(8) daemon will	 remove	 after
       applying	header_checks(5) and before invoking Milter applications.  The
       default setting is compatible with Postfix < 3.0.

       Specify a list of header	names, separated by comma or space.  Names are
       matched	in  a  case-insensitive	 manner.  The list of supported	header
       names is	limited	only by	available memory.

       This feature is available in Postfix 3.0	and later.

message_reject_characters (default: empty)
       The set of characters that Postfix will reject in message content.  The
       usual C-like escape sequences are recognized: \a	\b \f \n \r \t \v \ddd
       (up to three octal digits) and \\.

       Note 1: this feature does not recognize text that requires MIME	decod-
       ing.  It	 inspects  raw	message	 content,  just	like header_checks and
       body_checks.

       Note 2: this  feature  is  disabled  with  "receive_override_options  =
       no_header_body_checks".

       Example:

       message_reject_characters = \0

       This feature is available in Postfix 2.3	and later.

message_size_limit (default: 10240000)
       The maximal size	in bytes of a message, including envelope information.
       The value cannot	exceed LONG_MAX	(typically, a 32-bit or	64-bit	signed
       integer).

       Note:  be  careful  when	making changes.	 Excessively small values will
       result in the loss of non-delivery notifications, when a	bounce message
       size exceeds the	local or remote	MTA's message size limit.

message_strip_characters (default: empty)
       The  set	 of  characters	that Postfix will remove from message content.
       The usual C-like	escape sequences are recognized: \a \b \f \n \r	\t  \v
       \ddd (up	to three octal digits) and \\.

       Note  1:	this feature does not recognize	text that requires MIME	decod-
       ing. It inspects	raw  message  content,	just  like  header_checks  and
       body_checks.

       Note  2:	 this  feature	is  disabled  with "receive_override_options =
       no_header_body_checks".

       Example:

       message_strip_characters	= \0

       This feature is available in Postfix 2.3	and later.

meta_directory (default: see 'postconf -d' output)
       The location of non-executable files that  are  shared  among  multiple
       Postfix	instances,  such  as  postfix-files,  dynamicmaps.cf,  and the
       multi-instance template files main.cf.proto and master.cf.proto.	  This
       directory  should  contain  only	Postfix-related	files.	Typically, the
       meta_directory parameter	has the	same default as	 the  config_directory
       parameter (/usr/local/etc/postfix or /usr/local/usr/local/etc/postfix).

       For  backwards  compatibility  with Postfix versions 2.6..2.11, specify
       "meta_directory = $daemon_directory" in main.cf	before	installing  or
       upgrading  Postfix,  or	specify	 "meta_directory  = /path/name"	on the
       "make makefiles", "make install"	or "make upgrade" command line.

       This feature is available in Postfix 3.0	and later.

milter_command_timeout (default: 30s)
       The time	limit for sending an SMTP command to a	Milter	(mail  filter)
       application, and	for receiving the response.

       Specify	a  non-zero  time  value  (an  integral	value plus an optional
       one-letter suffix that specifies	the time unit).	 Time units:  s	 (sec-
       onds),  m  (minutes), h (hours),	d (days), w (weeks).  The default time
       unit is s (seconds).

       This feature is available in Postfix 2.3	and later.

milter_connect_macros (default:	see postconf -d	output)
       The macros that are sent	to Milter  (mail  filter)  applications	 after
       completion  of  an  SMTP	 connection.  See  MILTER_README for a list of
       available macro names and their meanings.

       This feature is available in Postfix 2.3	and later.

milter_connect_timeout (default: 30s)
       The time	limit for connecting to	a Milter  (mail	 filter)  application,
       and for negotiating protocol options.

       Specify	a  non-zero  time  value  (an  integral	value plus an optional
       one-letter suffix that specifies	the time unit).	 Time units:  s	 (sec-
       onds),  m  (minutes), h (hours),	d (days), w (weeks).  The default time
       unit is s (seconds).

       This feature is available in Postfix 2.3	and later.

milter_content_timeout (default: 300s)
       The time	limit for sending message content to a	Milter	(mail  filter)
       application, and	for receiving the response.

       Specify	a  non-zero  time  value  (an  integral	value plus an optional
       one-letter suffix that specifies	the time unit).	 Time units:  s	 (sec-
       onds),  m  (minutes), h (hours),	d (days), w (weeks).  The default time
       unit is s (seconds).

       This feature is available in Postfix 2.3	and later.

milter_data_macros (default: see postconf -d output)
       The macros that are sent	to version 4 or	higher	Milter	(mail  filter)
       applications  after the SMTP DATA command. See MILTER_README for	a list
       of available macro names	and their meanings.

       This feature is available in Postfix 2.3	and later.

milter_default_action (default:	tempfail)
       The default action when a Milter	(mail filter) response is  unavailable
       (for example, bad Postfix configuration or Milter failure). Specify one
       of the following:

       accept Proceed as if the	mail filter was	not present.

       reject Reject all further commands in this  session  with  a  permanent
	      status code.

       tempfail
	      Reject  all  further  commands  in this session with a temporary
	      status code.

       quarantine
	      Like "accept", but freeze	 the  message  in  the	"hold"	queue.
	      Available	with Postfix 2.6 and later.

       This feature is available in Postfix 2.3	and later.

milter_end_of_data_macros (default: see	postconf -d output)
       The macros that are sent	to Milter (mail	filter)	applications after the
       message end-of-data. See	MILTER_README for a list  of  available	 macro
       names and their meanings.

       This feature is available in Postfix 2.3	and later.

milter_end_of_header_macros (default: see postconf -d output)
       The macros that are sent	to Milter (mail	filter)	applications after the
       end of the message header. See MILTER_README for	a  list	 of  available
       macro names and their meanings.

       This feature is available in Postfix 2.5	and later.

milter_header_checks (default: empty)
       Optional	 lookup	 tables	for content inspection of message headers that
       are produced by Milter applications.  See the  header_checks(5)	manual
       page available actions. Currently, PREPEND is not implemented.

       The  following  example sends all mail that is marked as	SPAM to	a spam
       handling	machine. Note that matches are case-insensitive	by default.

       /usr/local/etc/postfix/main.cf:
	   milter_header_checks	= pcre:$config_directory/milter_header_checks

       /usr/local/etc/postfix/milter_header_checks:
	   /^X-SPAM-FLAG:\s+YES/ FILTER	mysmtp:sanitizer.example.com:25

       The milter_header_checks	mechanism could	also be	used for allowlisting.
       For  example  it	 could	be  used  to skip heavy	content	inspection for
       DKIM-signed mail	from known friendly domains.

       This feature is available in Postfix 2.7, and as	an optional patch  for
       Postfix 2.6.

milter_helo_macros (default: see postconf -d output)
       The macros that are sent	to Milter (mail	filter)	applications after the
       SMTP HELO or EHLO command. See MILTER_README for	a  list	 of  available
       macro names and their meanings.

       This feature is available in Postfix 2.3	and later.

milter_macro_daemon_name (default: $myhostname)
       The  {daemon_name}  macro  value	for Milter (mail filter) applications.
       See MILTER_README for a list of available macro names and  their	 mean-
       ings.

       This feature is available in Postfix 2.3	and later.

milter_macro_defaults (default:	empty)
       Optional	list of	name=value pairs that specify default values for arbi-
       trary macros that Postfix may send to Milter applications.   These  de-
       faults  are  used  when	there is no corresponding information from the
       message delivery	context.

       Specify name=value or {name=value} pairs	separated by comma  or	white-
       space.	Enclose	 a  pair in "{}" when a	value contains comma or	white-
       space (this form	ignores	whitespace after the enclosing "{", around the
       "=", and	before the enclosing "}").

       This feature is available in Postfix 3.1	and later.

milter_macro_v (default: $mail_name $mail_version)
       The  {v}	 macro	value for Milter (mail filter) applications.  See MIL-
       TER_README for a	list of	available macro	names and their	meanings.

       This feature is available in Postfix 2.3	and later.

milter_mail_macros (default: see postconf -d output)
       The macros that are sent	to Milter (mail	filter)	applications after the
       SMTP MAIL FROM command. See MILTER_README for a list of available macro
       names and their meanings.

       This feature is available in Postfix 2.3	and later.

milter_protocol	(default: 6)
       The mail	filter protocol	version	and optional protocol  extensions  for
       communication  with  a Milter application; prior	to Postfix 2.6 the de-
       fault protocol is 2. Postfix sends this version number during the  ini-
       tial  protocol  handshake.   It should match the	version	number that is
       expected	by the mail filter application (or by its Milter library).

       Protocol	versions:

       2      Use Sendmail 8 mail filter  protocol  version  2	(default  with
	      Sendmail version 8.11 .. 8.13 and	Postfix	version	2.3 ..	2.5).

       3      Use Sendmail 8 mail filter protocol version 3.

       4      Use Sendmail 8 mail filter protocol version 4.

       6      Use  Sendmail  8	mail  filter  protocol version 6 (default with
	      Sendmail version 8.14 and	Postfix	version	2.6).

       Protocol	extensions:

       no_header_reply
	      Specify this when	the Milter application will not	reply for each
	      individual message header.

       This feature is available in Postfix 2.3	and later.

milter_rcpt_macros (default: see postconf -d output)
       The macros that are sent	to Milter (mail	filter)	applications after the
       SMTP RCPT TO command. See MILTER_README for a list of  available	 macro
       names and their meanings.

       This feature is available in Postfix 2.3	and later.

milter_unknown_command_macros (default:	see postconf -d	output)
       The  macros  that  are sent to version 3	or higher Milter (mail filter)
       applications after an unknown SMTP command.  See	 MILTER_README	for  a
       list of available macro names and their meanings.

       This feature is available in Postfix 2.3	and later.

mime_boundary_length_limit (default: 2048)
       The maximal length of MIME multipart boundary strings. The MIME proces-
       sor is unable to	distinguish between boundary strings that do not  dif-
       fer in the first	$mime_boundary_length_limit characters.

       This feature is available in Postfix 2.0	and later.

mime_header_checks (default: $header_checks)
       Optional	 lookup	 tables	for content inspection of MIME related message
       headers,	as described in	the header_checks(5) manual page.

       This feature is available in Postfix 2.0	and later.

mime_nesting_limit (default: 100)
       The maximal recursion level that	the MIME processor will	handle.	 Post-
       fix refuses mail	that is	nested deeper than the specified limit.

       This feature is available in Postfix 2.0	and later.

minimal_backoff_time (default: 300s)
       The  minimal time between attempts to deliver a deferred	message; prior
       to Postfix 2.4 the default value	was 1000s.

       This parameter also limits the time an unreachable destination is  kept
       in the short-term, in-memory, destination status	cache.

       This parameter should be	set greater than or equal to $queue_run_delay.
       See also	$maximal_backoff_time.

       Specify a non-zero time value  (an  integral  value  plus  an  optional
       one-letter  suffix  that	specifies the time unit).  Time	units: s (sec-
       onds), m	(minutes), h (hours), d	(days),	w (weeks).  The	 default  time
       unit is s (seconds).

multi_instance_directories (default: empty)
       An  optional  list  of  non-default  Postfix configuration directories;
       these directories belong	to additional Postfix instances	that share the
       Postfix executable files	and documentation with the default Postfix in-
       stance, and that	are started, stopped, etc., together with the  default
       Postfix	instance.   Specify  a list of pathnames separated by comma or
       whitespace.

       When $multi_instance_directories	is empty, the postfix(1) command  runs
       in single-instance mode and operates on a single	Postfix	instance only.
       Otherwise, the postfix(1) command runs in multi-instance	mode  and  in-
       vokes   the   multi-instance   manager  specified  with	the  multi_in-
       stance_wrapper parameter. The multi-instance manager in	turn  executes
       postfix(1)  commands  for  the default instance and for all Postfix in-
       stances in $multi_instance_directories.

       Currently, this parameter setting is ignored  except  for  the  default
       main.cf file.

       This feature is available in Postfix 2.6	and later.

multi_instance_enable (default:	no)
       Allow  this  Postfix  instance  to  be  started,	 stopped,  etc.,  by a
       multi-instance manager.	By default, new	instances  are	created	 in  a
       safe  state  that prevents them from being started inadvertently.  This
       parameter is reserved for the multi-instance manager.

       This feature is available in Postfix 2.6	and later.

multi_instance_group (default: empty)
       The optional instance group name	of  this  Postfix  instance.  A	 group
       identifies  closely-related  Postfix  instances that the	multi-instance
       manager can start, stop,	etc., as a unit.  This parameter  is  reserved
       for the multi-instance manager.

       This feature is available in Postfix 2.6	and later.

multi_instance_name (default: empty)
       The  optional instance name of this Postfix instance. This name becomes
       also the	default	value for the syslog_name parameter.

       This feature is available in Postfix 2.6	and later.

multi_instance_wrapper (default: empty)
       The pathname of a multi-instance	manager	command	 that  the  postfix(1)
       command	invokes	when the multi_instance_directories parameter value is
       non-empty. The pathname may be followed by  initial  command  arguments
       separated  by  whitespace;  shell metacharacters	such as	quotes are not
       supported in this context.

       The postfix(1) command invokes the manager command with the  postfix(1)
       non-option  command arguments on	the manager command line, and with all
       installation configuration parameters exported into the manager command
       process environment. The	manager	command	in turn	invokes	the postfix(1)
       command for individual Postfix instances	as "postfix  -c	 config_direc-
       tory command".

       This feature is available in Postfix 2.6	and later.

multi_recipient_bounce_reject_code (default: 550)
       The  numerical  Postfix	SMTP  server  response code when a remote SMTP
       client request is blocked by the	reject_multi_recipient_bounce restric-
       tion.

       Do  not	change	this  unless  you have a complete understanding	of RFC
       5321.

       This feature is available in Postfix 2.1	and later.

mydestination (default:	$myhostname, localhost.$mydomain, localhost)
       The list	of domains that	are delivered via  the	$local_transport  mail
       delivery	 transport.  By	 default this is the Postfix local(8) delivery
       agent which looks up all	recipients in  /etc/passwd  and	 /etc/aliases.
       The  SMTP  server  validates  recipient	addresses  with	$local_recipi-
       ent_maps	and rejects non-existent recipients. See also the local	domain
       class in	the ADDRESS_CLASS_README file.

       The  default  mydestination value specifies names for the local machine
       only.  On a mail	domain gateway,	you should also	include	$mydomain.

       The $local_transport delivery method is	also  selected	for  mail  ad-
       dressed	to  user@[the.net.work.address]	of the mail system (the	IP ad-
       dresses specified with the inet_interfaces and proxy_interfaces parame-
       ters).

       Warnings:

       o      Do  not specify the names	of virtual domains - those domains are
	      specified	elsewhere. See VIRTUAL_README for more information.

       o      Do not specify the names of domains that this machine is	backup
	      MX host for. See STANDARD_CONFIGURATION_README for how to	set up
	      backup MX	hosts.

       o      By default, the Postfix SMTP server rejects mail for  recipients
	      not  listed  with	 the  local_recipient_maps parameter.  See the
	      postconf(5) manual for a description of the local_recipient_maps
	      and unknown_local_recipient_reject_code parameters.

       Specify	a  list	 of host or domain names, "/file/name" or "type:table"
       patterns, separated by commas and/or whitespace.	A "/file/name" pattern
       is  replaced  by	 its  contents;	a "type:table" lookup table is matched
       when a name matches a lookup key	(the lookup result is ignored).	  Con-
       tinue long lines	by starting the	next line with whitespace.

       Examples:

       mydestination = $myhostname, localhost.$mydomain	$mydomain
       mydestination = $myhostname, localhost.$mydomain	www.$mydomain, ftp.$mydomain

mydomain (default: see postconf	-d output)
       The  internet  domain  name of this mail	system.	 The default is	to use
       $myhostname minus the first component, or  "localdomain"	 (Postfix  2.3
       and  later).   $mydomain	is used	as a default value for many other con-
       figuration parameters.

       Example:

       mydomain	= domain.tld

myhostname (default: see postconf -d output)
       The internet hostname of	this mail system. The default is  to  use  the
       fully-qualified	domain	name  (FQDN) from gethostname(), or to use the
       non-FQDN	result from gethostname() and append  ".$mydomain".   $myhost-
       name  is	 used  as a default value for many other configuration parame-
       ters.

       Example:

       myhostname = host.example.com

mynetworks (default: see postconf -d output)
       The list	of "trusted" remote SMTP clients  that	have  more  privileges
       than "strangers".

       In particular, "trusted"	SMTP clients are allowed to relay mail through
       Postfix.	 See the smtpd_relay_restrictions parameter description	in the
       postconf(5) manual.

       You  can	specify	the list of "trusted" network addresses	by hand	or you
       can let Postfix do it for you (which is the default).  See the descrip-
       tion of the mynetworks_style parameter for more information.

       If  you specify the mynetworks list by hand, Postfix ignores the	mynet-
       works_style setting.

       Specify a list of network addresses or network/netmask patterns,	 sepa-
       rated  by commas	and/or whitespace. Continue long lines by starting the
       next line with whitespace.

       The netmask specifies the number	of bits	in the network part of a  host
       address.	  You  can also	specify	"/file/name" or	"type:table" patterns.
       A "/file/name" pattern is replaced  by  its  contents;  a  "type:table"
       lookup table is matched when a table entry matches a lookup string (the
       lookup result is	ignored).

       The list	is matched left	to right, and the search stops	on  the	 first
       match.	Specify	"!pattern" to exclude an address or network block from
       the list. The form "!/file/name"	is supported only in  Postfix  version
       2.4 and later.

       Note  1:	Pattern	matching of domain names is controlled by the presence
       or absence of "mynetworks" in the parent_domain_matches_subdomains  pa-
       rameter value.

       Note 2: IP version 6 address information	must be	specified inside [] in
       the mynetworks value, and in files  specified  with  "/file/name".   IP
       version	6  addresses contain the ":" character,	and would otherwise be
       confused	with a "type:table" pattern.

       Note 3: CIDR ranges cannot be specified in hash tables.	Use  cidr  ta-
       bles if CIDR ranges are used.

       Examples:

       mynetworks = 127.0.0.0/8	168.100.189.0/28
       mynetworks = !192.168.0.1, 192.168.0.0/28
       mynetworks = 127.0.0.0/8	168.100.189.0/28 [::1]/128 [2001:240:587::]/64
       mynetworks = $config_directory/mynetworks
       mynetworks = hash:$config_directory/network_table
       mynetworks = cidr:$config_directory/network_table.cidr

mynetworks_style (default: Postfix >= 3.0: host, Postfix < 3.0:	subnet)
       The  method to generate the default value for the mynetworks parameter.
       This is the list	of trusted networks for	relay access control etc.

       o      Specify "mynetworks_style	= host"	when  Postfix  should  "trust"
	      only the local machine.

       o      Specify  "mynetworks_style = subnet" when	Postfix	should "trust"
	      remote SMTP clients in the same IP subnetworks as	the local  ma-
	      chine.   On  Linux,  this	 works	correctly only with interfaces
	      specified	with the "ifconfig" or "ip" command.

       o      Specify "mynetworks_style	= class" when Postfix  should  "trust"
	      remote  SMTP  clients in the same	IP class A/B/C networks	as the
	      local machine.  Caution: this may	cause Postfix to "trust"  your
	      entire  provider's network.  Instead, specify an explicit	mynet-
	      works list by hand, as described with the	mynetworks  configura-
	      tion parameter.

myorigin (default: $myhostname)
       The domain name that locally-posted mail	appears	to come	from, and that
       locally posted mail is delivered	to. The	default, $myhostname, is  ade-
       quate for small sites.  If you run a domain with	multiple machines, you
       should (1) change this to $mydomain and (2) set up a domain-wide	 alias
       database	that aliases each user to user@that.users.mailhost.

       Example:

       myorigin	= $mydomain

nested_header_checks (default: $header_checks)
       Optional	lookup tables for content inspection of	non-MIME message head-
       ers in attached messages, as described in the  header_checks(5)	manual
       page.

       This feature is available in Postfix 2.0	and later.

newaliases_path	(default: see postconf -d output)
       Sendmail	 compatibility	feature	 that  specifies  the  location	of the
       newaliases(1) command. This command can be used to rebuild the local(8)
       aliases(5) database.

non_fqdn_reject_code (default: 504)
       The  numerical  Postfix SMTP server reply code when a client request is
       rejected	by the	reject_non_fqdn_helo_hostname,	reject_non_fqdn_sender
       or reject_non_fqdn_recipient restriction.

non_smtpd_milters (default: empty)
       A  list of Milter (mail filter) applications for	new mail that does not
       arrive via the Postfix smtpd(8) server. This includes local  submission
       via the sendmail(1) command line, new mail that arrives via the Postfix
       qmqpd(8)	server,	and old	mail that is re-injected into the  queue  with
       "postsuper  -r".	  Specify  space or comma as a separator. See the MIL-
       TER_README document for details.

       This feature is available in Postfix 2.3	and later.

notify_classes (default: resource, software)
       The list	of error classes that are reported to  the  postmaster.	 These
       postmaster notifications	do not replace user notifications. The default
       is to report only the most serious problems. The	paranoid may  wish  to
       turn  on	 the policy (UCE and mail relaying) and	protocol error (broken
       mail software) reports.

       NOTE: postmaster	notifications  may  contain  confidential  information
       such  as	 SASL passwords	or message content.  It	is the system adminis-
       trator's	responsibility to treat	such information with care.

       The error classes are:

       bounce (also implies 2bounce)
	      Send the postmaster copies of the	headers	of bounced  mail,  and
	      send transcripts of SMTP sessions	when Postfix rejects mail. The
	      notification  is	sent  to  the  address	specified   with   the
	      bounce_notice_recipient  configuration parameter (default: post-
	      master).

       2bounce
	      Send undeliverable bounced mail to the postmaster. The notifica-
	      tion  is	sent  to  the  address	specified with the 2bounce_no-
	      tice_recipient configuration parameter (default: postmaster).

       data   Send the postmaster a transcript of the SMTP session with	an er-
	      ror  because a critical data file	was unavailable. The notifica-
	      tion is sent to the address specified with the  error_notice_re-
	      cipient configuration parameter (default:	postmaster).
	      This feature is available	in Postfix 2.9 and later.

       delay  Send  the	 postmaster copies of the headers of delayed mail (see
	      delay_warning_time). The notification is	sent  to  the  address
	      specified	 with the delay_notice_recipient configuration parame-
	      ter (default: postmaster).

       policy Send the postmaster a transcript of  the	SMTP  session  when  a
	      client request was rejected because of (UCE) policy. The notifi-
	      cation is	sent to	 the  address  specified  with	the  error_no-
	      tice_recipient configuration parameter (default: postmaster).

       protocol
	      Send  the	postmaster a transcript	of the SMTP session in case of
	      client or	server protocol	errors.	The notification  is  sent  to
	      the address specified with the error_notice_recipient configura-
	      tion parameter (default: postmaster).

       resource
	      Inform the postmaster of mail  not  delivered  due  to  resource
	      problems.	  The  notification  is	 sent to the address specified
	      with the	error_notice_recipient	configuration  parameter  (de-
	      fault: postmaster).

       software
	      Inform  the  postmaster  of  mail	 not delivered due to software
	      problems.	 The notification is sent  to  the  address  specified
	      with  the	 error_notice_recipient	 configuration	parameter (de-
	      fault: postmaster).

       Examples:

       notify_classes =	bounce,	delay, policy, protocol, resource, software
       notify_classes =	2bounce, resource, software

openssl_path (default: openssl)
       The location of the OpenSSL command line	program	openssl(1).   This  is
       used  by	 the "postfix tls" command to create private keys, certificate
       signing requests, self-signed certificates, and to compute  public  key
       digests	for  DANE  TLSA	records.  In multi-instance environments, this
       parameter is always determined from the configuration  of  the  default
       Postfix instance.

       Example:

	   /usr/local/etc/postfix/main.cf:
	       # NetBSD	pkgsrc:
	       openssl_path = /usr/pkg/bin/openssl
	       # Local build:
	       openssl_path = /usr/local/bin/openssl

       This feature is available in Postfix 3.1	and later.

owner_request_special (default:	yes)
       Enable  special	treatment for owner-listname entries in	the aliases(5)
       file, and don't split owner-listname and	listname-request  address  lo-
       calparts	 when  the recipient_delimiter is set to "-".  This feature is
       useful for mailing lists.

parent_domain_matches_subdomains (default: see postconf	-d output)
       A list of Postfix features where	the pattern "example.com" also matches
       subdomains  of  example.com,  instead  of requiring an explicit ".exam-
       ple.com"	pattern.  This is planned  backwards  compatibility:   eventu-
       ally,  all  Postfix  features  are expected to require explicit ".exam-
       ple.com"	style patterns when you	really want to match subdomains.

       The following Postfix feature names are supported.

       Postfix version 1.0 and later
	      debug_peer_list,	  fast_flush_domains,	  mynetworks,	  per-
	      mit_mx_backup_networks, relay_domains, transport_maps

       Postfix version 1.1 and later
	      qmqpd_authorized_clients,	smtpd_access_maps,

       Postfix version 2.8 and later
	      postscreen_access_list

       Postfix version 3.0 and later
	      smtpd_client_event_limit_exceptions

permit_mx_backup_networks (default: empty)
       Restrict	 the  use  of the permit_mx_backup SMTP	access feature to only
       domains whose primary MX	hosts match the	listed networks.  The  parame-
       ter  value  syntax  is the same as with the mynetworks parameter; note,
       however,	that the default value is empty.

       Pattern matching	of domain names	is controlled by the presence  or  ab-
       sence  of "permit_mx_backup_networks" in	the parent_domain_matches_sub-
       domains parameter value.

pickup_service_name (default: pickup)
       The name	of the pickup(8) service. This service	picks  up  local  mail
       submissions from	the Postfix maildrop queue.

       This feature is available in Postfix 2.0	and later.

pipe_delivery_status_filter (default: $default_delivery_status_filter)
       Optional	 filter	 for the pipe(8) delivery agent	to change the delivery
       status code or explanatory text of successful or	unsuccessful  deliver-
       ies.  See default_delivery_status_filter	for details.

       This feature is available in Postfix 3.0	and later.

plaintext_reject_code (default:	450)
       The  numerical  Postfix SMTP server response code when a	request	is re-
       jected by the reject_plaintext_session restriction.

       This feature is available in Postfix 2.3	and later.

postlog_service_name (default: postlog)
       The name	of the postlogd(8) service entry in master.cf.	 This  service
       appends logfile records to the file specified with the maillog_file pa-
       rameter.

       This feature is available in Postfix 3.4	and later.

postlogd_watchdog_timeout (default: 10s)
       How much	time a postlogd(8) process may take to process a  request  be-
       fore  it	 is  terminated	by a built-in watchdog timer. This is a	safety
       mechanism that prevents postlogd(8) from	becoming non-responsive	due to
       a bug in	Postfix	itself or in system software. This limit cannot	be set
       under 10s.

       Specify a non-zero time value  (an  integral  value  plus  an  optional
       one-letter  suffix  that	specifies the time unit).  Time	units: s (sec-
       onds), m	(minutes), h (hours), d	(days),	w (weeks).  The	 default  time
       unit is s (seconds).

       This feature is available in Postfix 3.4	and later.

postmulti_control_commands (default: reload flush)
       The  postfix(1)	commands that the postmulti(1) instance	manager	treats
       as "control" commands, that operate on  running	instances.  For	 these
       commands, disabled instances are	skipped.

       This feature is available in Postfix 2.6	and later.

postmulti_start_commands (default: start)
       The  postfix(1)	commands that the postmulti(1) instance	manager	treats
       as  "start"  commands.  For  these  commands,  disabled	instances  are
       "checked"  rather  than	"started", and failure to "start" a member in-
       stance of an instance group will	abort the start-up of later instances.

       This feature is available in Postfix 2.6	and later.

postmulti_stop_commands	(default: see postconf -d output)
       The postfix(1) commands that the	postmulti(1) instance  manager	treats
       as "stop" commands. For these commands, disabled	instances are skipped,
       and enabled instances are processed in reverse order.

       This feature is available in Postfix 2.6	and later.

postscreen_access_list (default: permit_mynetworks)
       Permanent  allow/denylist  for  remote  SMTP   client   IP   addresses.
       postscreen(8) searches this list	immediately after a remote SMTP	client
       connects.  Specify a comma- or whitespace-separated  list  of  commands
       (in  upper  or  lower case) or lookup tables. The search	stops upon the
       first command that fires	for the	client IP address.

	permit_mynetworks
	      Allowlist	the client and terminate the search if the  client  IP
	      address  matches	$mynetworks.  Do not subject the client	to any
	      before/after 220 greeting	tests.	Pass  the  connection  immedi-
	      ately to a Postfix SMTP server process.
	      Pattern  matching	 of domain names is controlled by the presence
	      or  absence  of  "postscreen_access_list"	 in   the   parent_do-
	      main_matches_subdomains parameter	value.

	type:table
	      Query the	specified lookup table.	Each table lookup result is an
	      access list, except that access  lists  inside  a	 table	cannot
	      specify type:table entries.
	      To  discourage  the use of hash, btree, etc. tables, there is no
	      support for substring matching like smtpd(8).  Use  CIDR	tables
	      instead.

	permit
	      Allowlist	 the  client  and terminate the	search.	Do not subject
	      the client to any	before/after 220 greeting tests. Pass the con-
	      nection immediately to a Postfix SMTP server process.

	reject
	      Denylist the client and terminate	the search. Subject the	client
	      to the action  configured	 with  the  postscreen_denylist_action
	      configuration parameter.

	dunno All  postscreen(8)  access lists implicitly have this command at
	      the end.
	      When  dunno is executed inside a lookup table, return  from  the
	      lookup table and evaluate	the next command.
	      When   dunno   is	executed outside a lookup table, terminate the
	      search, and subject the client to	 the  configured  before/after
	      220 greeting tests.

       Example:

       /usr/local/etc/postfix/main.cf:
	   postscreen_access_list = permit_mynetworks,
	       cidr:$config_directory/postscreen_access.cidr
	   # Postfix < 3.6 use postscreen_blacklist_action.
	   postscreen_denylist_action =	enforce

       /usr/local/etc/postfix/postscreen_access.cidr:
	   # Rules are evaluated in the	order as specified.
	   # Denylist 192.168.*	except 192.168.0.1.
	   192.168.0.1	       dunno
	   192.168.0.0/16      reject

       This feature is available in Postfix 2.8.

postscreen_allowlist_interfaces	(default: static:all)
       A  list	of  local  postscreen(8)  server  IP addresses where a non-al-
       lowlisted remote	SMTP client can	obtain postscreen(8)'s	temporary  al-
       lowlist status. This status is required before the client can talk to a
       Postfix	SMTP  server  process.	 By  default,  a  client  can	obtain
       postscreen(8)'s	allowlist  status on any local postscreen(8) server IP
       address.

       When postscreen(8) listens on both primary and backup MX	addresses, the
       postscreen_allowlist_interfaces parameter can be	configured to give the
       temporary allowlist status only when a client connects to a primary  MX
       address.	 Once  a  client  is allowlisted it can	talk to	a Postfix SMTP
       server on any address. Thus, clients that connect only to backup	MX ad-
       dresses	will  never  become  allowlisted, and will never be allowed to
       talk to a Postfix SMTP server process.

       Specify a list of network addresses or network/netmask patterns,	 sepa-
       rated  by commas	and/or whitespace. The netmask specifies the number of
       bits in the network part	of a host  address.  Continue  long  lines  by
       starting	the next line with whitespace.

       You   can  also	specify	 "/file/name"  or  "type:table"	 patterns.   A
       "/file/name" pattern is replaced	by its contents; a "type:table"	lookup
       table is	matched	when a table entry matches a lookup string (the	lookup
       result is ignored).

       The list	is matched left	to right, and the search stops	on  the	 first
       match.  Specify	"!pattern" to exclude an address or network block from
       the list.

       Note: IP	version	6 address information must be specified	inside	[]  in
       the  postscreen_allowlist_interfaces value, and in files	specified with
       "/file/name".  IP version 6 addresses contain the  ":"  character,  and
       would otherwise be confused with	a "type:table" pattern.

       Example:

       /usr/local/etc/postfix/main.cf:
	   # Don't allowlist connections to the	backup IP address.
	   # Postfix < 3.6 use postscreen_whitelist_interfaces.
	   postscreen_allowlist_interfaces = !168.100.189.8, static:all

       This feature is available in Postfix 3.6	and later.

       Available as postscreen_whitelist_interfaces in Postfix 2.9 - 3.5.

postscreen_bare_newline_action (default: ignore)
       The  action  that postscreen(8) takes when a remote SMTP	client sends a
       bare newline character, that is,	a newline not preceded by carriage re-
       turn.  Specify one of the following:

       ignore Ignore  the failure of this test.	Allow other tests to complete.
	      Do not repeat this test before the result	from some  other  test
	      expires.	 This option is	useful for testing and collecting sta-
	      tistics without blocking mail permanently.

       enforce
	      Allow other tests	to complete. Reject attempts to	 deliver  mail
	      with  a 550 SMTP reply, and log the helo/sender/recipient	infor-
	      mation.  Repeat this test	the next time the client connects.

       drop   Drop the connection immediately with a 521  SMTP	reply.	Repeat
	      this test	the next time the client connects.

       This feature is available in Postfix 2.8.

postscreen_bare_newline_enable (default: no)
       Enable  "bare newline" SMTP protocol tests in the postscreen(8) server.
       These tests are expensive: a remote SMTP	client must  disconnect	 after
       it passes the test, before it can talk to a real	Postfix	SMTP server.

       This feature is available in Postfix 2.8.

postscreen_bare_newline_ttl (default: 30d)
       The  amount  of time that postscreen(8) will use	the result from	a suc-
       cessful "bare newline" SMTP protocol test. During this time, the	client
       IP  address  is	excluded from this test. The default is	long because a
       remote SMTP client must disconnect after	it passes the test, before  it
       can talk	to a real Postfix SMTP server.

       Specify	a  non-zero  time  value  (an  integral	value plus an optional
       one-letter suffix that specifies	the time unit).	 Time units:  s	 (sec-
       onds),  m  (minutes), h (hours),	d (days), w (weeks).  The default time
       unit is d (days).

       This feature is available in Postfix 2.8.

postscreen_blacklist_action (default: ignore)
       Renamed to postscreen_denylist_action in	Postfix	3.6.

       This feature is available in Postfix 2.8	- 3.5.

postscreen_cache_cleanup_interval (default: 12h)
       The amount of time between postscreen(8)	 cache	cleanup	 runs.	 Cache
       cleanup	increases  the load on the cache database and should therefore
       not be run frequently. This feature requires that  the  cache  database
       supports	 the "delete" and "sequence" operators.	 Specify a zero	inter-
       val to disable cache cleanup.

       After each cache	cleanup	run, the postscreen(8) daemon logs the	number
       of  entries  that were retained and dropped. A cleanup run is logged as
       "partial" when the daemon  terminates  early  after  "postfix  reload",
       "postfix	stop", or no requests for $max_idle seconds.

       Specify	a  non-negative	time value (an integral	value plus an optional
       one-letter suffix that specifies	the time unit).	 Time units:  s	 (sec-
       onds),  m  (minutes), h (hours),	d (days), w (weeks).  The default time
       unit is h (hours).

       This feature is available in Postfix 2.8.

postscreen_cache_map (default: btree:$data_directory/postscreen_cache)
       Persistent storage for the postscreen(8)	server decisions.

       To share	a  postscreen(8)  cache	 between  multiple  postscreen(8)  in-
       stances,	 use "postscreen_cache_map = proxy:btree:/path/to/file".  This
       requires	Postfix	version	2.9 or later; earlier proxymap(8)  implementa-
       tions  don't support cache cleanup. For an alternative approach see the
       memcache_table(5) manpage.

       This feature is available in Postfix 2.8.

postscreen_cache_retention_time	(default: 7d)
       The amount of time that postscreen(8) will cache	an  expired  temporary
       allowlist  entry	before it is removed. This prevents clients from being
       logged as "NEW" just because their cache	entry expired an hour ago.  It
       also  prevents  the cache from filling up with clients that passed some
       deep protocol test once and never came back.

       Specify a non-zero time value  (an  integral  value  plus  an  optional
       one-letter  suffix  that	specifies the time unit).  Time	units: s (sec-
       onds), m	(minutes), h (hours), d	(days),	w (weeks).  The	 default  time
       unit is d (days).

       This feature is available in Postfix 2.8.

postscreen_client_connection_count_limit    (default:	 $smtpd_client_connec-
       tion_count_limit)
       How many	simultaneous connections any remote SMTP client	is allowed  to
       have  with the postscreen(8) daemon. By default,	this limit is the same
       as with the Postfix SMTP	server.	Note that the triage process can  take
       several	seconds,  with	the time spent in postscreen_greet_wait	delay,
       and with	the time spent talking to  the	postscreen(8)  built-in	 dummy
       SMTP protocol engine.

       This feature is available in Postfix 2.8.

postscreen_command_count_limit (default: 20)
       The  limit  on  the  total  number  of  commands	 per  SMTP session for
       postscreen(8)'s built-in	SMTP protocol engine.  This SMTP engine	defers
       or  rejects all attempts	to deliver mail, therefore there is no need to
       enforce separate	limits on the number of	junk commands and  error  com-
       mands.

       This feature is available in Postfix 2.8.

postscreen_command_filter (default: $smtpd_command_filter)
       A  mechanism  to	 transform  commands  from  remote  SMTP clients.  See
       smtpd_command_filter for	further	details.

       This feature is available in Postfix 2.8	and later.

postscreen_command_time_limit (default:	normal:	300s, overload:	10s)
       The time	limit to read an  entire  command  line	 with  postscreen(8)'s
       built-in	SMTP protocol engine.

       This feature is available in Postfix 2.8.

postscreen_denylist_action (default: ignore)
       The action that postscreen(8) takes when	a remote SMTP client is	perma-
       nently denylisted with the postscreen_access_list  parameter.   Specify
       one of the following:

       ignore (default)
	      Ignore  this result. Allow other tests to	complete.  Repeat this
	      test the next time the client connects.  This option  is	useful
	      for testing and collecting statistics without blocking mail.

       enforce
	      Allow  other  tests to complete. Reject attempts to deliver mail
	      with a 550 SMTP reply, and log the helo/sender/recipient	infor-
	      mation.  Repeat this test	the next time the client connects.

       drop   Drop  the	 connection  immediately with a	521 SMTP reply.	Repeat
	      this test	the next time the client connects.

       This feature is available in Postfix 3.6	and later.

       Available as postscreen_blacklist_action	in Postfix 2.8 - 3.5.

postscreen_disable_vrfy_command	(default: $disable_vrfy_command)
       Disable the SMTP	VRFY command in	the postscreen(8)  daemon.   See  dis-
       able_vrfy_command for details.

       This feature is available in Postfix 2.8.

postscreen_discard_ehlo_keyword_address_maps	   (default:	   $smtpd_dis-
       card_ehlo_keyword_address_maps)
       Lookup tables, indexed by the remote SMTP client	address, with case in-
       sensitive  lists	 of  EHLO  keywords (pipelining, starttls, auth, etc.)
       that the	postscreen(8) server will not send in the EHLO response	 to  a
       remote  SMTP  client. See smtpd_discard_ehlo_keywords for details.  The
       table is	not searched by	hostname for robustness	reasons.

       This feature is available in Postfix 2.8	and later.

postscreen_discard_ehlo_keywords (default: $smtpd_discard_ehlo_keywords)
       A case insensitive list of EHLO keywords	(pipelining,  starttls,	 auth,
       etc.)  that the postscreen(8) server will not send in the EHLO response
       to a remote SMTP	client.	See smtpd_discard_ehlo_keywords	for details.

       This feature is available in Postfix 2.8	and later.

postscreen_dnsbl_action	(default: ignore)
       The action that postscreen(8) takes when	a remote  SMTP	client's  com-
       bined  DNSBL  score is equal to or greater than a threshold (as defined
       with the	postscreen_dnsbl_sites and postscreen_dnsbl_threshold  parame-
       ters).  Specify one of the following:

       ignore (default)
	      Ignore  the failure of this test.	Allow other tests to complete.
	      Repeat this test the next	time the client	connects.  This	option
	      is useful	for testing and	collecting statistics without blocking
	      mail.

       enforce
	      Allow other tests	to complete. Reject attempts to	 deliver  mail
	      with  a 550 SMTP reply, and log the helo/sender/recipient	infor-
	      mation.  Repeat this test	the next time the client connects.

       drop   Drop the connection immediately with a 521  SMTP	reply.	Repeat
	      this test	the next time the client connects.

       This feature is available in Postfix 2.8.

postscreen_dnsbl_allowlist_threshold (default: 0)
       Allow  a	 remote	 SMTP client to	skip "before" and "after 220 greeting"
       protocol	tests, based on	its combined DNSBL score as defined  with  the
       postscreen_dnsbl_sites parameter.

       Specify	a  negative value to enable this feature. When a client	passes
       the postscreen_dnsbl_allowlist_threshold	without	 having	 failed	 other
       tests,  all  pending  or	disabled tests are flagged as completed	with a
       time-to-live value equal	to postscreen_dnsbl_ttl.  When a test was  al-
       ready  completed, its time-to-live value	is updated if it was less than
       postscreen_dnsbl_ttl.

       This feature is available in Postfix 3.6	and later.

       Available as postscreen_dnsbl_whitelist_threshold  in  Postfix  2.11  -
       3.5.

postscreen_dnsbl_max_ttl					     (default:
       ${postscreen_dnsbl_ttl?{$postscreen_dnsbl_ttl}:{1}}h)
       The maximum amount of time that postscreen(8) will use the result  from
       a  successful  DNS-based	 reputation test before	a client IP address is
       required	to pass	that test again. If the	DNS reply specifies a  shorter
       TTL  value,  that  value	 will  be used unless it would be smaller than
       postscreen_dnsbl_min_ttl.

       Specify a non-zero time value  (an  integral  value  plus  an  optional
       one-letter  suffix  that	specifies the time unit).  Time	units: s (sec-
       onds), m	(minutes), h (hours), d	(days),	w (weeks).  The	 default  time
       unit is h (hours).

       This  feature is	available in Postfix 3.1. The default setting is back-
       wards-compatible	with older Postfix versions.

postscreen_dnsbl_min_ttl (default: 60s)
       The minimum amount of time that postscreen(8) will use the result  from
       a  successful  DNS-based	 reputation test before	a client IP address is
       required	to pass	that test again. If the	DNS reply specifies  a	larger
       TTL  value,  that  value	 will  be  used	unless it would	be larger than
       postscreen_dnsbl_max_ttl.

       Specify a non-zero time value  (an  integral  value  plus  an  optional
       one-letter  suffix  that	specifies the time unit).  Time	units: s (sec-
       onds), m	(minutes), h (hours), d	(days),	w (weeks).  The	 default  time
       unit is s (seconds).

       This feature is available in Postfix 3.1.

postscreen_dnsbl_reply_map (default: empty)
       A  mapping  from	 an  actual  DNSBL domain name which includes a	secret
       password, to the	DNSBL domain name that postscreen will reply with when
       it  rejects  mail.   When  no mapping is	found, the actual DNSBL	domain
       will be used.

       For maximal stability it	is best	to use a file that is read into	memory
       such as pcre:, regexp: or texthash: (texthash: is similar to hash:, ex-
       cept a) there is	no need	to run postmap(1) before the file can be used,
       and b) texthash:	does not detect	changes	after the file is read).

       Example:

       /usr/local/etc/postfix/main.cf:
	   postscreen_dnsbl_reply_map =	texthash:$config_directory/dnsbl_reply

       /usr/local/etc/postfix/dnsbl_reply:
	  secret.zen.spamhaus.org      zen.spamhaus.org

       This feature is available in Postfix 2.8.

postscreen_dnsbl_sites (default: empty)
       Optional	 list  of  DNS allow/denylist domains, filters and weight fac-
       tors. When the list is non-empty,  the  dnsblog(8)  daemon  will	 query
       these  domains  with  the  IP  addresses	 of  remote  SMTP clients, and
       postscreen(8) will update  an  SMTP  client's  DNSBL  score  with  each
       non-error reply.

       Caution:	when postscreen	rejects	mail, it replies with the DNSBL	domain
       name. Use the postscreen_dnsbl_reply_map	feature	to hide	"password" in-
       formation in DNSBL domain names.

       When  a client's	score is equal to or greater than the threshold	speci-
       fied with postscreen_dnsbl_threshold, postscreen(8) can drop  the  con-
       nection with the	remote SMTP client.

       Specify	a  list	of domain=filter*weight	entries, separated by comma or
       whitespace.

       o      When no "=filter"	 is  specified,	 postscreen(8)	will  use  any
	      non-error	DNSBL reply.  Otherwise, postscreen(8) uses only DNSBL
	      replies that match the filter. The filter	has the	form  d.d.d.d,
	      where  each  d is	a number, or a pattern inside [] that contains
	      one or more ";"-separated	numbers	or number..number ranges.

       o      When no "*weight"	is specified, postscreen(8) increments the re-
	      mote SMTP	client's DNSBL score by	1.  Otherwise, the weight must
	      be an integral number,  and  postscreen(8)  adds	the  specified
	      weight to	the remote SMTP	client's DNSBL score.  Specify a nega-
	      tive number for allowlisting.

       o      When one postscreen_dnsbl_sites entry  produces  multiple	 DNSBL
	      responses, postscreen(8) applies the weight at most once.

       Examples:

       To  use	example.com  as	a high-confidence blocklist, and to block mail
       with example.net	and example.org	only when both agree:

       postscreen_dnsbl_threshold = 2
       postscreen_dnsbl_sites =	example.com*2, example.net, example.org

       To filter only DNSBL replies containing 127.0.0.4:

       postscreen_dnsbl_sites =	example.com=127.0.0.4

       This feature is available in Postfix 2.8.

postscreen_dnsbl_threshold (default: 1)
       The inclusive lower bound for blocking a	remote SMTP client,  based  on
       its combined DNSBL score	as defined with	the postscreen_dnsbl_sites pa-
       rameter.

       This feature is available in Postfix 2.8.

postscreen_dnsbl_timeout (default: 10s)
       The time	limit for DNSBL	or DNSWL lookups. This is  separate  from  the
       timeouts	 in  the  dnsblog(8)  daemon  which  are defined by system re-
       solver(3) routines.

       Specify a non-zero time value  (an  integral  value  plus  an  optional
       one-letter  suffix  that	specifies the time unit).  Time	units: s (sec-
       onds), m	(minutes), h (hours), d	(days),	w (weeks).  The	 default  time
       unit is s (seconds).

       This feature is available in Postfix 3.0.

postscreen_dnsbl_ttl (default: 1h)
       The  amount  of time that postscreen(8) will use	the result from	a suc-
       cessful DNS-based reputation test before	a client  IP  address  is  re-
       quired to pass that test	again.

       Specify	a  non-zero  time  value  (an  integral	value plus an optional
       one-letter suffix that specifies	the time unit).	 Time units:  s	 (sec-
       onds),  m  (minutes), h (hours),	d (days), w (weeks).  The default time
       unit is h (hours).

       This feature is available  in  Postfix  2.8-3.0.	 It  was  replaced  by
       postscreen_dnsbl_max_ttl	in Postfix 3.1.

postscreen_dnsbl_whitelist_threshold (default: 0)
       Renamed to postscreen_dnsbl_allowlist_threshold in Postfix 3.6.

       This feature is available in Postfix 2.11 - 3.5.

postscreen_enforce_tls (default: $smtpd_enforce_tls)
       Mandatory  TLS:	announce  STARTTLS support to remote SMTP clients, and
       require that clients  use  TLS  encryption.   See  smtpd_postscreen_en-
       force_tls for details.

       This  feature  is  available in Postfix 2.8 and later.  Preferably, use
       postscreen_tls_security_level instead.

postscreen_expansion_filter (default: see postconf -d output)
       List of characters that are permitted in	 postscreen_reject_footer  at-
       tribute expansions.  See	smtpd_expansion_filter for further details.

       This feature is available in Postfix 2.8	and later.

postscreen_forbidden_commands (default:	$smtpd_forbidden_commands)
       List  of	 commands that the postscreen(8) server	considers in violation
       of the SMTP protocol.  See  smtpd_forbidden_commands  for  syntax,  and
       postscreen_non_smtp_command_action for possible actions.

       This feature is available in Postfix 2.8.

postscreen_greet_action	(default: ignore)
       The  action  that  postscreen(8)	takes when a remote SMTP client	speaks
       before	its   turn   within    the    time    specified	   with	   the
       postscreen_greet_wait parameter.	 Specify one of	the following:

       ignore (default)
	      Ignore  the failure of this test.	Allow other tests to complete.
	      Repeat this test the next	time the client	connects.  This	option
	      is useful	for testing and	collecting statistics without blocking
	      mail.

       enforce
	      Allow other tests	to complete. Reject attempts to	 deliver  mail
	      with  a 550 SMTP reply, and log the helo/sender/recipient	infor-
	      mation.  Repeat this test	the next time the client connects.

       drop   Drop the connection immediately with a 521  SMTP	reply.	Repeat
	      this test	the next time the client connects.

       In either case, postscreen(8) will not allowlist	the remote SMTP	client
       IP address.

       This feature is available in Postfix 2.8.

postscreen_greet_banner	(default: $smtpd_banner)
       The  text  in  the  optional   "220-text..."   server   response	  that
       postscreen(8)  sends  ahead  of	the  real  Postfix  SMTP server's "220
       text..."	response, in an	attempt	to confuse bad SMTP  clients  so  that
       they  speak  before  their turn (pre-greet).  Specify an	empty value to
       disable this feature.

       This feature is available in Postfix 2.8.

postscreen_greet_ttl (default: 1d)
       The amount of time that postscreen(8) will use the result from  a  suc-
       cessful	PREGREET  test.	During this time, the client IP	address	is ex-
       cluded from this	test. The default is relatively	short, because a  good
       client can immediately talk to a	real Postfix SMTP server.

       Specify	a  non-zero  time  value  (an  integral	value plus an optional
       one-letter suffix that specifies	the time unit).	 Time units:  s	 (sec-
       onds),  m  (minutes), h (hours),	d (days), w (weeks).  The default time
       unit is d (days).

       This feature is available in Postfix 2.8.

postscreen_greet_wait (default:	normal:	6s, overload: 2s)
       The amount of time that postscreen(8) will wait for an SMTP  client  to
       send a command before its turn, and for DNS blocklist lookup results to
       arrive (default:	up to 2	seconds	under stress, up to 6  seconds	other-
       wise).

       Specify	a  non-zero  time  value  (an  integral	value plus an optional
       one-letter suffix that specifies	the time unit).	 Time units:  s	 (sec-
       onds),  m  (minutes), h (hours),	d (days), w (weeks).  The default time
       unit is s (seconds).

       This feature is available in Postfix 2.8.

postscreen_helo_required (default: $smtpd_helo_required)
       Require that a remote SMTP client sends HELO or EHLO before  commencing
       a MAIL transaction.

       This feature is available in Postfix 2.8.

postscreen_non_smtp_command_action (default: drop)
       The  action  that  postscreen(8)	 takes when a remote SMTP client sends
       non-SMTP	commands as specified with  the	 postscreen_forbidden_commands
       parameter.  Specify one of the following:

       ignore Ignore  the failure of this test.	Allow other tests to complete.
	      Do not repeat this test before the result	from some  other  test
	      expires.	 This option is	useful for testing and collecting sta-
	      tistics without blocking mail permanently.

       enforce
	      Allow other tests	to complete. Reject attempts to	 deliver  mail
	      with  a 550 SMTP reply, and log the helo/sender/recipient	infor-
	      mation.  Repeat this test	the next time the client connects.

       drop   Drop the connection immediately with a 521  SMTP	reply.	Repeat
	      this  test the next time the client connects. This action	is the
	      same as with the Postfix SMTP server's  smtpd_forbidden_commands
	      feature.

       This feature is available in Postfix 2.8.

postscreen_non_smtp_command_enable (default: no)
       Enable  "non-SMTP  command"  tests  in  the postscreen(8) server. These
       tests are expensive: a client must disconnect after it passes the test,
       before it can talk to a real Postfix SMTP server.

       This feature is available in Postfix 2.8.

postscreen_non_smtp_command_ttl	(default: 30d)
       The  amount  of time that postscreen(8) will use	the result from	a suc-
       cessful "non_smtp_command" SMTP protocol	test. During  this  time,  the
       client  IP  address is excluded from this test. The default is long be-
       cause a client must disconnect after it passes the test,	before it  can
       talk to a real Postfix SMTP server.

       Specify	a  non-zero  time  value  (an  integral	value plus an optional
       one-letter suffix that specifies	the time unit).	 Time units:  s	 (sec-
       onds),  m  (minutes), h (hours),	d (days), w (weeks).  The default time
       unit is d (days).

       This feature is available in Postfix 2.8.

postscreen_pipelining_action (default: enforce)
       The action that postscreen(8) takes when	a  remote  SMTP	 client	 sends
       multiple	 commands  instead  of sending one command and waiting for the
       server to respond.  Specify one of the following:

       ignore Ignore the failure of this test. Allow other tests to  complete.
	      Do  not  repeat this test	before the result from some other test
	      expires.	This option is useful for testing and collecting  sta-
	      tistics without blocking mail permanently.

       enforce
	      Allow  other  tests to complete. Reject attempts to deliver mail
	      with a 550 SMTP reply, and log the helo/sender/recipient	infor-
	      mation.  Repeat this test	the next time the client connects.

       drop   Drop  the	 connection  immediately with a	521 SMTP reply.	Repeat
	      this test	the next time the client connects.

       This feature is available in Postfix 2.8.

postscreen_pipelining_enable (default: no)
       Enable "pipelining" SMTP	protocol tests in  the	postscreen(8)  server.
       These  tests  are  expensive:  a	 good  client must disconnect after it
       passes the test,	before it can talk to a	real Postfix SMTP server.

       This feature is available in Postfix 2.8.

postscreen_pipelining_ttl (default: 30d)
       The amount of time that postscreen(8) will use the result from  a  suc-
       cessful	"pipelining"  SMTP protocol test. During this time, the	client
       IP address is excluded from this	test. The default is  long  because  a
       good  client  must  disconnect  after it	passes the test, before	it can
       talk to a real Postfix SMTP server.

       Specify a non-zero time value  (an  integral  value  plus  an  optional
       one-letter  suffix  that	specifies the time unit).  Time	units: s (sec-
       onds), m	(minutes), h (hours), d	(days),	w (weeks).  The	 default  time
       unit is d (days).

       This feature is available in Postfix 2.8.

postscreen_post_queue_limit (default: $default_process_limit)
       The number of clients that can be waiting for service from a real Post-
       fix SMTP	server process.	When this queue	is full, all clients will  re-
       ceive a 421 response.

       This feature is available in Postfix 2.8.

postscreen_pre_queue_limit (default: $default_process_limit)
       The  number  of non-allowlisted clients that can	be waiting for a deci-
       sion whether they will receive service from a real Postfix SMTP	server
       process.	 When this queue is full, all non-allowlisted clients will re-
       ceive a 421 response.

       This feature is available in Postfix 2.8.

postscreen_reject_footer (default: $smtpd_reject_footer)
       Optional	information that is appended after a 4XX or 5XX	 postscreen(8)
       server response.	See smtpd_reject_footer	for further details.

       This feature is available in Postfix 2.8	and later.

postscreen_reject_footer_maps (default:	$smtpd_reject_footer_maps)
       Optional	 lookup	 table for information that is appended	after a	4XX or
       5XX postscreen(8) server	 response.  See	 smtpd_reject_footer_maps  for
       further details.

       This feature is available in Postfix 3.4	and later.

postscreen_tls_security_level (default:	$smtpd_tls_security_level)
       The  SMTP  TLS  security	 level	for  the  postscreen(8)	server;	when a
       non-empty value is specified, this overrides  the  obsolete  parameters
       postscreen_use_tls   and	 postscreen_enforce_tls.  See  smtpd_tls_secu-
       rity_level for details.

       This feature is available in Postfix 2.8	and later.

postscreen_upstream_proxy_protocol (default: empty)
       The name	of the proxy protocol used by  an  optional  before-postscreen
       proxy  agent.  When  a proxy agent is used, this	protocol conveys local
       and  remote  address  and  port	information.  Specify  "postscreen_up-
       stream_proxy_protocol  =	 haproxy" to enable the	haproxy	protocol; ver-
       sion 2 is supported with	Postfix	3.5 and	later.

       This feature is available in Postfix 2.10 and later.

postscreen_upstream_proxy_timeout (default: 5s)
       The time	limit for the proxy protocol specified with the	postscreen_up-
       stream_proxy_protocol parameter.

       This feature is available in Postfix 2.10 and later.

postscreen_use_tls (default: $smtpd_use_tls)
       Opportunistic  TLS:  announce  STARTTLS support to remote SMTP clients,
       but do not require that clients use TLS encryption.

       This feature is available in Postfix 2.8	and  later.   Preferably,  use
       postscreen_tls_security_level instead.

postscreen_watchdog_timeout (default: 10s)
       How  much  time a postscreen(8) process may take	to respond to a	remote
       SMTP client command or to perform a cache operation before it is	termi-
       nated  by  a  built-in watchdog timer.  This is a safety	mechanism that
       prevents	postscreen(8) from becoming non-responsive due	to  a  bug  in
       Postfix itself or in system software.  To avoid false alarms and	unnec-
       essary cache corruption this limit cannot be set	under 10s.

       Specify a non-zero time value  (an  integral  value  plus  an  optional
       one-letter  suffix  that	specifies the time unit).  Time	units: s (sec-
       onds), m	(minutes), h (hours), d	(days),	w (weeks).  The	 default  time
       unit is s (seconds).

       This feature is available in Postfix 2.8.

postscreen_whitelist_interfaces	(default: static:all)
       Renamed to postscreen_allowlist_interfaces in Postfix 3.6.

       This feature is available in Postfix 2.9	- 3.5.

prepend_delivered_header (default: command, file, forward)
       The message delivery contexts where the Postfix local(8)	delivery agent
       prepends	a Delivered-To:	 message header	with the address that the mail
       was  delivered  to. This	information is used for	mail delivery loop de-
       tection.

       By default, the Postfix local delivery agent prepends  a	 Delivered-To:
       header  when  forwarding	mail and when delivering to file (mailbox) and
       command.	Turning	off the	Delivered-To: header when forwarding  mail  is
       not recommended.

       Specify zero or more of forward,	file, or command.

       Example:

       prepend_delivered_header	= forward

process_id (read-only)
       The process ID of a Postfix command or daemon process.

process_id_directory (default: pid)
       The  location  of Postfix PID files relative to $queue_directory.  This
       is a read-only parameter.

process_name (read-only)
       The process name	of a Postfix command or	daemon process.

propagate_unmatched_extensions (default: canonical, virtual)
       What address lookup tables copy an address extension  from  the	lookup
       key to the lookup result.

       For   example,	with  a	 virtual(5)  mapping  of  "joe@example.com  =_
       joe.user@example.net", the address "joe+foo@example.com"	would  rewrite
       to "joe.user+foo@example.net".

       Specify	zero or	more of	canonical, virtual, alias, forward, include or
       generic.	These cause address extension propagation  with	 canonical(5),
       virtual(5),  and	 aliases(5) maps, with local(8)	.forward and :include:
       file lookups, and with smtp(8) generic maps, respectively.

       Note: enabling this feature for types other than	canonical and  virtual
       is  likely to cause problems when mail is forwarded to other sites, es-
       pecially	with mail that is sent to a mailing list exploder address.

       Examples:

       propagate_unmatched_extensions =	canonical, virtual, alias,
	       forward,	include
       propagate_unmatched_extensions =	canonical, virtual

proxy_interfaces (default: empty)
       The network interface addresses that this mail system receives mail  on
       by way of a proxy or network address translation	unit.

       This feature is available in Postfix 2.0	and later.

       You must	specify	your "outside" proxy/NAT addresses when	your system is
       a backup	MX host	for other domains, otherwise mail delivery loops  will
       happen when the primary MX host is down.

       Example:

       proxy_interfaces	= 1.2.3.4

proxy_read_maps	(default: see postconf -d output)
       The  lookup tables that the proxymap(8) server is allowed to access for
       the read-only service.

       Specify zero or more "type:name"	lookup tables, separated by whitespace
       or comma.  Table	references that	don't begin with proxy:	are ignored.

       This feature is available in Postfix 2.0	and later.

proxy_write_maps (default: see postconf	-d output)
       The  lookup tables that the proxymap(8) server is allowed to access for
       the read-write service. Postfix-owned local database  files  should  be
       stored  under  the Postfix-owned	data_directory.	 Table references that
       don't begin with	proxy: are ignored.

       This feature is available in Postfix 2.5	and later.

proxymap_service_name (default:	proxymap)
       The name	of the proxymap	read-only table	lookup service.	 This  service
       is normally implemented by the proxymap(8) daemon.

       This feature is available in Postfix 2.6	and later.

proxywrite_service_name	(default: proxywrite)
       The  name of the	proxywrite read-write table lookup service.  This ser-
       vice is normally	implemented by the proxymap(8) daemon.

       This feature is available in Postfix 2.6	and later.

qmgr_clog_warn_time (default: 300s)
       The minimal delay between warnings that a specific destination is clog-
       ging up the Postfix active queue. Specify 0 to disable.

       Specify	a  non-negative	time value (an integral	value plus an optional
       one-letter suffix that specifies	the time unit).	 Time units:  s	 (sec-
       onds),  m  (minutes), h (hours),	d (days), w (weeks).  The default time
       unit is s (seconds).

       This feature is enabled with the	helpful_warnings parameter.

       This feature is available in Postfix 2.0	and later.

qmgr_daemon_timeout (default: 1000s)
       How much	time a Postfix queue manager process may take to handle	a  re-
       quest before it is terminated by	a built-in watchdog timer.

       Specify	a  non-zero  time  value  (an  integral	value plus an optional
       one-letter suffix that specifies	the time unit).	 Time units:  s	 (sec-
       onds),  m  (minutes), h (hours),	d (days), w (weeks).  The default time
       unit is s (seconds).

       This feature is available in Postfix 2.8	and later.

qmgr_fudge_factor (default: 100)
       Obsolete	feature: the percentage	of delivery resources that a busy mail
       system will use up for delivery of a large mailing  list	message.

       This feature exists only	in the oqmgr(8)	old queue manager. The current
       queue manager solves the	problem	in a better way.

qmgr_ipc_timeout (default: 60s)
       The time	limit for the queue manager to	send  or  receive  information
       over an internal	communication channel.	The purpose is to break	out of
       deadlock	situations. If the time	limit is exceeded the software	either
       retries or aborts the operation.

       Specify	a  non-zero  time  value  (an  integral	value plus an optional
       one-letter suffix that specifies	the time unit).	 Time units:  s	 (sec-
       onds),  m  (minutes), h (hours),	d (days), w (weeks).  The default time
       unit is s (seconds).

       This feature is available in Postfix 2.8	and later.

qmgr_message_active_limit (default: 20000)
       The maximal number of messages in the active queue.

qmgr_message_recipient_limit (default: 20000)
       The maximal number of recipients	held in	memory by  the	Postfix	 queue
       manager,	 and the maximal size of the short-term, in-memory "dead" des-
       tination	status cache.

qmgr_message_recipient_minimum (default: 10)
       The minimal number of in-memory recipients for any message. This	 takes
       priority	 over  any  other in-memory recipient limits (i.e., the	global
       qmgr_message_recipient_limit and	the per	transport _recipient_limit) if
       necessary. The minimum value allowed for	this parameter is 1.

qmqpd_authorized_clients (default: empty)
       What  remote  QMQP  clients  are	allowed	to connect to the Postfix QMQP
       server port.

       By default, no client is	allowed	to use the service.  This  is  because
       the QMQP	server will relay mail to any destination.

       Specify	a  list	 of  client  patterns. A list pattern specifies	a host
       name, a domain name, an internet	address, or  a	network/mask  pattern,
       where  the mask specifies the number of bits in the network part.  When
       a pattern specifies a file name,	its contents are substituted  for  the
       file  name; when	a pattern is a "type:table" table specification, table
       lookup is used instead.

       Patterns	are separated by whitespace and/or commas. In order to reverse
       the  result,  precede a pattern with an exclamation point (!). The form
       "!/file/name" is	supported only in Postfix version 2.4 and later.

       Pattern matching	of domain names	is controlled by the presence  or  ab-
       sence of	"qmqpd_authorized_clients" in the parent_domain_matches_subdo-
       mains parameter value.

       Example:

       qmqpd_authorized_clients	= !192.168.0.1,	192.168.0.0/24

qmqpd_client_port_logging (default: no)
       Enable logging of the remote QMQP client	port in	addition to the	 host-
       name and	IP address. The	logging	format is "host[address]:port".

       This feature is available in Postfix 2.5	and later.

qmqpd_error_delay (default: 1s)
       How  long  the Postfix QMQP server will pause before sending a negative
       reply to	the remote QMQP	client.	The purpose is to slow	down  confused
       or malicious clients.

       Specify	a  non-negative	time value (an integral	value plus an optional
       one-letter suffix that specifies	the time unit).	 Time units:  s	 (sec-
       onds),  m  (minutes), h (hours),	d (days), w (weeks).  The default time
       unit is s (seconds).

qmqpd_timeout (default:	300s)
       The time	limit for sending or receiving information over	 the  network.
       If  a  read or write operation blocks for more than $qmqpd_timeout sec-
       onds the	Postfix	QMQP server gives up and disconnects.

       Specify a non-zero time value  (an  integral  value  plus  an  optional
       one-letter  suffix  that	specifies the time unit).  Time	units: s (sec-
       onds), m	(minutes), h (hours), d	(days),	w (weeks).  The	 default  time
       unit is s (seconds).

queue_directory	(default: see postconf -d output)
       The location of the Postfix top-level queue directory. This is the root
       directory of Postfix daemon processes that run chrooted.

queue_file_attribute_count_limit (default: 100)
       The maximal number of (name=value) attributes that may be stored	 in  a
       Postfix queue file. The limit is	enforced by the	cleanup(8) server.

       This feature is available in Postfix 2.0	and later.

queue_minfree (default:	0)
       The minimal amount of free space	in bytes in the	queue file system that
       is needed to receive mail.  This	is currently used by the Postfix  SMTP
       server to decide	if it will accept any mail at all.

       By default, the Postfix SMTP server rejects MAIL	FROM commands when the
       amount of free space is less than 1.5*$message_size_limit (Postfix ver-
       sion  2.1  and  later).	 To specify a higher minimum free space	limit,
       specify a queue_minfree value that is at	least 1.5*$message_size_limit.

       With Postfix versions 2.0 and earlier, a	queue_minfree  value  of  zero
       means there is no minimum required amount of free space.

queue_run_delay	(default: 300s)
       The  time  between  deferred queue scans	by the queue manager; prior to
       Postfix 2.4 the default value was 1000s.

       This parameter should be	set  less  than	 or  equal  to	$minimal_back-
       off_time. See also $maximal_backoff_time.

       Specify	a  non-zero  time  value  (an  integral	value plus an optional
       one-letter suffix that specifies	the time unit).	 Time units:  s	 (sec-
       onds),  m  (minutes), h (hours),	d (days), w (weeks).  The default time
       unit is s (seconds).

queue_service_name (default: qmgr)
       The name	of the qmgr(8) service.	This service manages the Postfix queue
       and schedules delivery requests.

       This feature is available in Postfix 2.0	and later.

rbl_reply_maps (default: empty)
       Optional	 lookup	tables with RBL	response templates. The	tables are in-
       dexed by	the RBL	domain name. By	default, Postfix uses the default tem-
       plate  as specified with	the default_rbl_reply configuration parameter.
       See there for a discussion of the syntax	of RBL reply templates.

       This feature is available in Postfix 2.0	and later.

readme_directory (default: see postconf	-d output)
       The location of Postfix README files that describe how to  build,  con-
       figure or operate a specific Postfix subsystem or feature.

receive_override_options (default: empty)
       Enable  or disable recipient validation,	built-in content filtering, or
       address mapping.	Typically, these are specified in  master.cf  as  com-
       mand-line arguments for the smtpd(8), qmqpd(8) or pickup(8) daemons.

       Specify	zero  or  more of the following	options.  The options override
       main.cf settings	and are	either implemented by smtpd(8),	 qmqpd(8),  or
       pickup(8) themselves, or	they are forwarded to the cleanup server.

       no_unknown_recipient_checks
	      Do  not  try  to	reject	unknown	recipients (SMTP server	only).
	      This is typically	specified AFTER	an external content filter.

       no_address_mappings
	      Disable canonical	address	mapping, virtual alias map  expansion,
	      address  masquerading, and automatic BCC (blind carbon-copy) re-
	      cipients.	This is	typically specified BEFORE an external content
	      filter.

       no_header_body_checks
	      Disable header/body_checks. This is typically specified AFTER an
	      external content filter.

       no_milters
	      Disable Milter (mail filter)  applications.  This	 is  typically
	      specified	AFTER an external content filter.

       Note: when the "BEFORE content filter" receive_override_options setting
       is specified in the main.cf file, specify the  "AFTER  content  filter"
       receive_override_options	setting	in master.cf (and vice versa).

       Examples:

       receive_override_options	=
	   no_unknown_recipient_checks,	no_header_body_checks
       receive_override_options	= no_address_mappings

       This feature is available in Postfix 2.1	and later.

recipient_bcc_maps (default: empty)
       Optional	 BCC (blind carbon-copy) address lookup	tables,	indexed	by re-
       cipient address.	 The BCC address (multiple results are not  supported)
       is added	when mail enters from outside of Postfix.

       Specify zero or more "type:name"	lookup tables, separated by whitespace
       or comma. Tables	will be	searched in the	specified order	until a	 match
       is found.

       The table search	order is as follows:

       o      Look  up	the  "user+extension@domain.tld" address including the
	      optional address extension.

       o      Look up the "user@domain.tld" address without the	 optional  ad-
	      dress extension.

       o      Look up the "user+extension" address local part when the recipi-
	      ent domain equals	$myorigin, $mydestination, $inet_interfaces or
	      $proxy_interfaces.

       o      Look  up the "user" address local	part when the recipient	domain
	      equals $myorigin,	$mydestination,	$inet_interfaces or $proxy_in-
	      terfaces.

       o      Look up the "@domain.tld"	part.

       Note:  with Postfix 2.3 and later the BCC address is added as if	it was
       specified with NOTIFY=NONE. The sender will not be  notified  when  the
       BCC  address  is	undeliverable, as long as all down-stream software im-
       plements	RFC 3461.

       Note: with Postfix 2.2 and earlier the sender will  unconditionally  be
       notified	when the BCC address is	undeliverable.

       Note:  automatic	 BCC  recipients  are  produced	only for new mail.  To
       avoid mailer loops, automatic BCC recipients are	 not  generated	 after
       Postfix	forwards  mail internally, or after Postfix generates mail it-
       self.

       Example:

       recipient_bcc_maps = hash:$config_directory/recipient_bcc

       After a change, run "postmap /usr/local/etc/postfix/recipient_bcc".

       This feature is available in Postfix 2.1	and later.

recipient_canonical_classes (default: envelope_recipient, header_recipient)
       What addresses are subject to recipient_canonical_maps address mapping.
       By  default, recipient_canonical_maps address mapping is	applied	to en-
       velope recipient	addresses, and to header recipient addresses.

       Specify one or more of: envelope_recipient, header_recipient

       This feature is available in Postfix 2.2	and later.

recipient_canonical_maps (default: empty)
       Optional	address	mapping	lookup tables for envelope and header  recipi-
       ent  addresses.	The table format and lookups are documented in canoni-
       cal(5).

       Note: $recipient_canonical_maps is processed before $canonical_maps.

       Example:

       recipient_canonical_maps	= hash:$config_directory/recipient_canonical

recipient_delimiter (default: empty)
       The set of characters that can separate	an  email  address  localpart,
       user  name,  or	a .forward file	name from its extension.  For example,
       with "recipient_delimiter = +", the software tries user+foo@example.com
       before  trying user@example.com,	user+foo before	trying user, and .for-
       ward+foo	before trying .forward.

       More formally, an email address localpart or  user  name	 is  separated
       from  its  extension  by	 the  first character that matches the recipi-
       ent_delimiter set. The delimiter	character and extension	 may  then  be
       used  to	 generate  an extended .forward	file name. This	implementation
       recognizes one delimiter	character and one extension per	email  address
       localpart  or email address. With Postfix 2.10 and earlier, the recipi-
       ent_delimiter specifies a single	character.

       See canonical(5), local(8), relocated(5)	and virtual(5) for the effects
       of  recipient_delimiter	on lookups in aliases, canonical, virtual, and
       relocated maps, and see	the  propagate_unmatched_extensions  parameter
       for propagating an extension from one email address to another.

       When used in command_execution_directory, forward_path, or luser_relay,
       ${recipient_delimiter} is replaced with the actual recipient  delimiter
       that was	found in the recipient email address (Postfix 2.11 and later),
       or it is	replaced with the main.cf recipient_delimiter parameter	 value
       (Postfix	2.10 and earlier).

       The  recipient_delimiter	 is  not applied to the	mailer-daemon address,
       the postmaster address, or the double-bounce address. With the  default
       "owner_request_special  = yes" setting, the recipient_delimiter is also
       not applied to addresses	with the special "owner-" prefix or  the  spe-
       cial "-request" suffix.

       Examples:

       # Handle	Postfix-style extensions.
       recipient_delimiter = +

       # Handle	both Postfix and qmail extensions (Postfix 2.11	and later).
       recipient_delimiter = +-

       # Use .forward for mail without address extension, and for mail with
       # an unrecognized address extension.
       forward_path = $home/.forward${recipient_delimiter}${extension},
	   $home/.forward

reject_code (default: 554)
       The  numerical  Postfix	SMTP  server  response code when a remote SMTP
       client request is rejected by the "reject" restriction.

       Do not change this unless you have  a  complete	understanding  of  RFC
       5321.

reject_tempfail_action (default: defer_if_permit)
       The  Postfix  SMTP server's action when a reject-type restriction fails
       due to a	temporary error	condition. Specify "defer" to defer the	remote
       SMTP client request immediately.	With the default "defer_if_permit" ac-
       tion, the Postfix SMTP server continues to look	for  opportunities  to
       reject  mail,  and defers the client request only if it would otherwise
       be accepted.

       For finer control, see:	unverified_recipient_tempfail_action,  unveri-
       fied_sender_tempfail_action,  unknown_address_tempfail_action,  and un-
       known_helo_hostname_tempfail_action.

       This feature is available in Postfix 2.6	and later.

relay_clientcerts (default: empty)
       List of tables with remote SMTP client-certificate fingerprints or pub-
       lic key fingerprints (Postfix 2.9 and later) for	which the Postfix SMTP
       server will allow access	with the permit_tls_clientcerts	feature.   The
       fingerprint  digest algorithm is	configurable via the smtpd_tls_finger-
       print_digest parameter (hard-coded as  md5  prior  to  Postfix  version
       2.5).

       The default algorithm is	sha256 with Postfix >= 3.6 and the compatibil-
       ity_level set to	3.6 or higher. With Postfix <= 3.5, the	default	 algo-
       rithm  is  md5.	 The best-practice algorithm is	now sha256. Recent ad-
       vances in hash function cryptanalysis have led to md5  and  sha1	 being
       deprecated  in favor of sha256.	However, as long as there are no known
       "second pre-image" attacks against the older algorithms,	their  use  in
       this context, though not	recommended, is	still likely safe.

       Postfix	lookup tables are in the form of (key, value) pairs.  Since we
       only need the key, the value can	be chosen freely, e.g.	 the  name  of
       the   user   or	host:  D7:04:2F:A7:0B:8C:A5:21:FA:31:77:E1:41:8A:EE:80
       lutzpc.at.home

       Example:

       relay_clientcerts = hash:$config_directory/relay_clientcerts

       For more	fine-grained control, use check_ccert_access to	select an  ap-
       propriate   access(5)   policy	for   each   client.	See   RESTRIC-
       TION_CLASS_README.

       This feature is available with Postfix version 2.2.

relay_destination_concurrency_limit   (default:	  $default_destination_concur-
       rency_limit)
       The  maximal  number of parallel	deliveries to the same destination via
       the relay message delivery transport. This limit	 is  enforced  by  the
       queue  manager.	The message delivery transport name is the first field
       in the entry in the master.cf file.

       This feature is available in Postfix 2.0	and later.

relay_destination_recipient_limit    (default:	  $default_destination_recipi-
       ent_limit)
       The  maximal number of recipients per message for the relay message de-
       livery transport. This limit is enforced	by the queue manager. The mes-
       sage  delivery  transport  name	is the first field in the entry	in the
       master.cf file.

       Setting this parameter to a value of  1	changes	 the  meaning  of  re-
       lay_destination_concurrency_limit from concurrency per domain into con-
       currency	per recipient.

       This feature is available in Postfix 2.0	and later.

relay_domains (default:	Postfix	>= 3.0:	empty, Postfix < 3.0: $mydestination)
       What destination	domains	(and subdomains	thereof) this system will  re-
       lay mail	to. For	details	about how the relay_domains value is used, see
       the description of the permit_auth_destination and reject_unauth_desti-
       nation SMTP recipient restrictions.

       Domains	that match $relay_domains are delivered	with the $relay_trans-
       port mail delivery transport. The SMTP server validates	recipient  ad-
       dresses with $relay_recipient_maps and rejects non-existent recipients.
       See also	the relay domains address class	 in  the  ADDRESS_CLASS_README
       file.

       Note: Postfix will not automatically forward mail for domains that list
       this  system  as	 their	primary	 or  backup  MX	 host.	See  the  per-
       mit_mx_backup restriction in the	postconf(5) manual page.

       Specify	a  list	 of  host  or  domain  names, "/file/name" patterns or
       "type:table" lookup tables,  separated  by  commas  and/or  whitespace.
       Continue	 long  lines  by  starting  the	 next  line with whitespace. A
       "/file/name" pattern is replaced	by its contents; a "type:table"	lookup
       table  is matched when a	(parent) domain	appears	as lookup key. Specify
       "!pattern" to exclude a domain from the list. The form "!/file/name" is
       supported only in Postfix version 2.4 and later.

       Pattern	matching  of domain names is controlled	by the presence	or ab-
       sence of	"relay_domains"	in the parent_domain_matches_subdomains	param-
       eter value.

relay_domains_reject_code (default: 554)
       The  numerical  Postfix SMTP server response code when a	client request
       is rejected by the reject_unauth_destination recipient restriction.

       Do not change this unless you have  a  complete	understanding  of  RFC
       5321.

relay_recipient_maps (default: empty)
       Optional	 lookup	 tables	 with  all valid addresses in the domains that
       match $relay_domains. Specify @domain as	a wild-card for	 domains  that
       have  no	valid recipient	list, and become a source of backscatter mail:
       Postfix accepts spam for	non-existent recipients	and then floods	 inno-
       cent  people  with undeliverable	mail.  Technically, tables listed with
       $relay_recipient_maps are used as lists:	Postfix	needs to know only  if
       a  lookup  string  is found or not, but it does not use the result from
       the table lookup.

       Specify zero or more "type:name"	lookup tables, separated by whitespace
       or  comma. Tables will be searched in the specified order until a match
       is found.

       If this parameter is non-empty, then the	Postfix	SMTP server  will  re-
       ject mail to unknown relay users. This feature is off by	default.

       See  also  the  relay domains address class in the ADDRESS_CLASS_README
       file.

       Example:

       relay_recipient_maps = hash:$config_directory/relay_recipients

       This feature is available in Postfix 2.0	and later.

relay_transport	(default: relay)
       The default mail	delivery transport and next-hop	destination for	remote
       delivery	 to domains listed with	$relay_domains.	In order of decreasing
       precedence, the nexthop destination  is	taken  from  $relay_transport,
       $sender_dependent_relayhost_maps, $relayhost, or	from the recipient do-
       main. This information can be overruled with the	transport(5) table.

       Specify a string	of the form transport:nexthop, where transport is  the
       name  of	 a mail	delivery transport defined in master.cf.  The :nexthop
       destination is optional;	its syntax is documented in the	manual page of
       the corresponding delivery agent.

       See  also  the  relay domains address class in the ADDRESS_CLASS_README
       file.

       This feature is available in Postfix 2.0	and later.

relayhost (default: empty)
       The next-hop destination(s) for non-local mail; overrides non-local do-
       mains  in  recipient  addresses.	This information is overruled with re-
       lay_transport, sender_dependent_default_transport_maps,	default_trans-
       port, sender_dependent_relayhost_maps and with the transport(5) table.

       On  an intranet,	specify	the organizational domain name.	If your	inter-
       nal DNS uses no MX records, specify the name of	the  intranet  gateway
       host instead.

       In  the case of SMTP or LMTP delivery, specify one or more destinations
       in the form of a	domain name, hostname, hostname:port, [hostname]:port,
       [hostaddress]  or [hostaddress]:port, separated by comma	or whitespace.
       The form	[hostname] turns off MX	 lookups.  Multiple  destinations  are
       supported in Postfix 3.5	and later.

       If  you're  connected via UUCP, see the UUCP_README file	for useful in-
       formation.

       Examples:

       relayhost = $mydomain
       relayhost = [gateway.example.com]
       relayhost = mail1.example:587, mail2.example:587
       relayhost = [an.ip.add.ress]

relocated_maps (default: empty)
       Optional	lookup tables with new contact information for	users  or  do-
       mains  that  no	longer	exist.	The table format and lookups are docu-
       mented in relocated(5).

       Specify zero or more "type:name"	lookup tables, separated by whitespace
       or  comma. Tables will be searched in the specified order until a match
       is found.

       If you use this feature,	run "postmap /usr/local/etc/postfix/relocated"
       to  build  the  necessary  DBM  or  DB file after change, then "postfix
       reload" to make the changes visible.

       Examples:

       relocated_maps =	dbm:$config_directory/relocated
       relocated_maps =	hash:$config_directory/relocated

remote_header_rewrite_domain (default: empty)
       Don't rewrite message headers from remote clients at all	when this  pa-
       rameter	is  empty;  otherwise,	rewrite	message	headers	and append the
       specified domain	name to	incomplete  addresses.	 The  local_header_re-
       write_clients parameter controls	what clients Postfix considers local.

       Examples:

       The  safe  setting:  append  "domain.invalid"  to incomplete header ad-
       dresses from remote SMTP	clients, so that  those	 addresses  cannot  be
       confused	with local addresses.

	   remote_header_rewrite_domain	= domain.invalid

       The default, purist, setting: don't rewrite headers from	remote clients
       at all.

	   remote_header_rewrite_domain	=

require_home_directory (default: no)
       Require that a local(8) recipient's home	directory exists  before  mail
       delivery	 is  attempted.	 By  default this test is disabled.  It	can be
       useful for environments that import home	directories to the mail	server
       (IMPORTING HOME DIRECTORIES IS NOT RECOMMENDED).

reset_owner_alias (default: no)
       Reset  the local(8) delivery agent's idea of the	owner-alias attribute,
       when delivering mail to a child alias that does not have	its own	 owner
       alias.

       This  feature is	available in Postfix 2.8 and later. With older Postfix
       releases, the behavior is as if this parameter is set to	"yes".

       As documented in	aliases(5), when an alias name has a  companion	 alias
       named  owner-name,  this	 will  replace the envelope sender address, so
       that delivery errors will be reported to	the owner alias	instead	of the
       sender. This configuration is recommended for mailing lists.

       A less known property of	the owner alias	is that	it also	forces the lo-
       cal(8) delivery agent to	write local and	remote	addresses  from	 alias
       expansion to a new queue	file, instead of attempting to deliver mail to
       local addresses as soon as they come out	of alias expansion.

       Writing local addresses from alias expansion to a new queue file	allows
       for robust handling of temporary	delivery errors: errors	with one local
       member have no effect on	deliveries to other members of the  list.   On
       the other hand, delivery	to local addresses as soon as they come	out of
       alias expansion is fragile: a temporary error with  one	local  address
       from alias expansion will cause the entire alias	to be expanded repeat-
       edly until the error goes away, or until	the  message  expires  in  the
       queue.	In that	case, a	problem	with one list member results in	multi-
       ple message deliveries to other list members.

       The  default  behavior  of  Postfix  2.8	 and  later  is	 to  keep  the
       owner-alias  attribute  of  the parent alias, when delivering mail to a
       child alias that	does not have its own owner  alias.  Then,  local  ad-
       dresses	from that child	alias will be written to a new queue file, and
       a temporary error with one local	address	will not  affect  delivery  to
       other mailing list members.

       Unfortunately,  older  Postfix releases reset the owner-alias attribute
       when delivering mail to a child alias that does not have	its own	 owner
       alias.  To  be  precise,	 this resets only the decision to create a new
       queue file, not the decision to override	the envelope  sender  address.
       The local(8) delivery agent then	attempts to deliver local addresses as
       soon as they come out of	child alias expansion.	If delivery to any ad-
       dress  from  child  alias expansion fails with a	temporary error	condi-
       tion, the entire	mailing	list may be expanded repeatedly	until the mail
       expires in the queue, resulting in multiple deliveries of the same mes-
       sage to mailing list members.

resolve_dequoted_address (default: yes)
       Resolve a recipient address safely instead of correctly,	by looking in-
       side quotes.

       By default, the Postfix address resolver	does not quote the address lo-
       calpart as per RFC 822, so that additional @ or % or !	operators  re-
       main  visible.  This behavior is	safe but it is also technically	incor-
       rect.

       If you specify "resolve_dequoted_address	= no", then  the  Postfix  re-
       solver  will  not know about additional @ etc. operators	in the address
       localpart. This opens opportunities for obscure mail relay attacks with
       user@domain@domain  addresses  when  Postfix provides backup MX service
       for Sendmail systems.

resolve_null_domain (default: no)
       Resolve an address that ends in the "@" null domain  as	if  the	 local
       hostname	were specified,	instead	of rejecting the address as invalid.

       This  feature  is available in Postfix 2.1 and later.  Earlier versions
       always resolve the null domain as the local hostname.

       The Postfix SMTP	server uses this feature to reject mail	from or	to ad-
       dresses	that  end  in the "@" null domain, and from addresses that re-
       write into a form that ends in the "@" null domain.

resolve_numeric_domain (default: no)
       Resolve "user@ipaddress"	as "user@[ipaddress]",	instead	 of  rejecting
       the address as invalid.

       This feature is available in Postfix 2.3	and later.

respectful_logging (default: see 'postconf -d' output)
       Avoid logging that implies white	is better than black. Instead use 'al-
       lowlist', 'denylist', and variations of those words.

       This feature is available in Postfix 3.6	and later.

rewrite_service_name (default: rewrite)
       The name	of the address rewriting service. This	service	 rewrites  ad-
       dresses	to  standard  form  and	 resolves  them	to a (delivery method,
       next-hop	host, recipient) triple.

       This feature is available in Postfix 2.0	and later.

sample_directory (default: /usr/local/etc/postfix)
       The name	of the directory with  example	Postfix	 configuration	files.
       Starting	 with  Postfix	2.1,  these  files have	been replaced with the
       postconf(5) manual page.

send_cyrus_sasl_authzid	(default: no)
       When authenticating to a	remote SMTP or LMTP server  with  the  default
       setting	"no",  send  no	SASL authoriZation ID (authzid); send only the
       SASL authentiCation ID (authcid)	plus the authcid's password.

       The non-default setting "yes" enables the  behavior  of	older  Postfix
       versions.   These  always send a	SASL authzid that is equal to the SASL
       authcid,	but this  causes  interoperability  problems  with  some  SMTP
       servers.

       This feature is available in Postfix 2.4.4 and later.

sender_based_routing (default: no)
       This  parameter	should	not  be	used. It was replaced by sender_depen-
       dent_relayhost_maps in Postfix version 2.3.

sender_bcc_maps	(default: empty)
       Optional	BCC (blind carbon-copy)	 address  lookup  tables,  indexed  by
       sender  address.	  The BCC address (multiple results are	not supported)
       is added	when mail enters from outside of Postfix.

       Specify zero or more "type:name"	lookup tables, separated by whitespace
       or  comma. Tables will be searched in the specified order until a match
       is found.

       The table search	order is as follows:

       o      Look up the "user+extension@domain.tld"  address	including  the
	      optional address extension.

       o      Look  up	the "user@domain.tld" address without the optional ad-
	      dress extension.

       o      Look up the "user+extension" address local part when the	sender
	      domain  equals  $myorigin,  $mydestination,  $inet_interfaces or
	      $proxy_interfaces.

       o      Look up the "user" address local part  when  the	sender	domain
	      equals $myorigin,	$mydestination,	$inet_interfaces or $proxy_in-
	      terfaces.

       o      Look up the "@domain.tld"	part.

       Note: with Postfix 2.3 and later	the BCC	address	is added as if it  was
       specified  with	NOTIFY=NONE.  The sender will not be notified when the
       BCC address is undeliverable, as	long as	all down-stream	 software  im-
       plements	RFC 3461.

       Note: with Postfix 2.2 and earlier the sender will be notified when the
       BCC address is undeliverable.

       Note: automatic BCC recipients are produced  only  for  new  mail.   To
       avoid  mailer  loops,  automatic	BCC recipients are not generated after
       Postfix forwards	mail internally, or after Postfix generates  mail  it-
       self.

       Example:

       sender_bcc_maps = hash:$config_directory/sender_bcc

       After a change, run "postmap /usr/local/etc/postfix/sender_bcc".

       This feature is available in Postfix 2.1	and later.

sender_canonical_classes (default: envelope_sender, header_sender)
       What  addresses	are  subject to	sender_canonical_maps address mapping.
       By default, sender_canonical_maps address mapping is applied  to	 enve-
       lope sender addresses, and to header sender addresses.

       Specify one or more of: envelope_sender,	header_sender

       This feature is available in Postfix 2.2	and later.

sender_canonical_maps (default:	empty)
       Optional	 address  mapping lookup tables	for envelope and header	sender
       addresses.  The table format and	 lookups  are  documented  in  canoni-
       cal(5).

       Example:	 you  want to rewrite the SENDER address "user@ugly.domain" to
       "user@pretty.domain", while still being able to send mail to the	RECIP-
       IENT address "user@ugly.domain".

       Note: $sender_canonical_maps is processed before	$canonical_maps.

       Example:

       sender_canonical_maps = hash:$config_directory/sender_canonical

sender_dependent_default_transport_maps	(default: empty)
       A  sender-dependent override for	the global default_transport parameter
       setting.	The tables are searched	by the	envelope  sender  address  and
       @domain.	 A  lookup result of DUNNO terminates the search without over-
       riding the global default_transport parameter setting.	This  informa-
       tion is overruled with the transport(5) table.

       Specify zero or more "type:name"	lookup tables, separated by whitespace
       or comma. Tables	will be	searched in the	specified order	until a	 match
       is found.

       Note:  this overrides default_transport,	not transport_maps, and	there-
       fore the	expected syntax	is that	of default_transport, not  the	syntax
       of  transport_maps.   Specifically,  this  does	not support the	trans-
       port_maps syntax	for null transport, null nexthop, or  null  email  ad-
       dresses.

       For  safety  reasons, this feature does not allow $number substitutions
       in regular expression maps.

       This feature is available in Postfix 2.7	and later.

sender_dependent_relayhost_maps	(default: empty)
       A sender-dependent override for the global relayhost parameter setting.
       The  tables  are	searched by the	envelope sender	address	and @domain. A
       lookup result of	DUNNO terminates the  search  without  overriding  the
       global relayhost	parameter setting (Postfix 2.6 and later). This	infor-
       mation  is   overruled	with   relay_transport,	  sender_dependent_de-
       fault_transport_maps,  default_transport	 and with the transport(5) ta-
       ble.

       Specify zero or more "type:name"	lookup tables, separated by whitespace
       or  comma. Tables will be searched in the specified order until a match
       is found.

       For safety reasons, this	feature	does not allow	$number	 substitutions
       in regular expression maps.

       This feature is available in Postfix 2.3	and later.

sendmail_fix_line_endings (default: always)
       Controls	 how  the Postfix sendmail command converts email message line
       endings from <CR><LF> into UNIX format (<LF>).

       always Always convert message lines ending in <CR><LF>. This setting is
	      the default with Postfix 2.9 and later.

       strict Convert message lines ending in <CR><LF> only if the first input
	      line ends	in <CR><LF>. This setting is backwards-compatible with
	      Postfix 2.8 and earlier.

       never  Never convert message lines ending in <CR><LF>. This setting ex-
	      ists for completeness only.

       This feature is available in Postfix 2.9	and later.

sendmail_path (default:	see postconf -d	output)
       A Sendmail compatibility	feature	that specifies	the  location  of  the
       Postfix	sendmail(1)  command.  This command can	be used	to submit mail
       into the	Postfix	queue.

service_name (read-only)
       The master.cf service name of a Postfix daemon  process.	 This  can  be
       used  to	 distinguish  the logging from different services that use the
       same program name.

       Example master.cf entries:

       # Distinguish inbound MTA logging from submission and smtps logging.
       smtp	 inet  n       -       n       -       -       smtpd
       submission inet n       -       n       -       -       smtpd
	   -o syslog_name=postfix/$service_name
       smtps	 inet  n       -       n       -       -       smtpd
	   -o syslog_name=postfix/$service_name

       # Distinguish outbound MTA logging from inbound relay logging.
       smtp	 unix  -       -       n       -       -       smtp
       relay	 unix  -       -       n       -       -       smtp
	   -o syslog_name=postfix/$service_name

service_throttle_time (default:	60s)
       How long	the Postfix master(8) waits before forking a server  that  ap-
       pears to	be malfunctioning.

       Specify	a  non-zero  time  value  (an  integral	value plus an optional
       one-letter suffix that specifies	the time unit).	 Time units:  s	 (sec-
       onds),  m  (minutes), h (hours),	d (days), w (weeks).  The default time
       unit is s (seconds).

setgid_group (default: postdrop)
       The group ownership of set-gid Postfix commands and  of	group-writable
       Postfix	directories.  When this	parameter value	is changed you need to
       re-run "postfix set-permissions"	(with Postfix version 2.0 and earlier:
       "/usr/local/etc/postfix/post-install set-permissions".

shlib_directory	(default: see 'postconf	-d' output)
       The location of Postfix dynamically-linked libraries (libpostfix-*.so),
       and the default location	of  Postfix  database  plugins	(postfix-*.so)
       that  have  a  relative	pathname  in  the  dynamicmaps.cf  file.   The
       shlib_directory	parameter  defaults  to	 "no"  when  Postfix   dynami-
       cally-linked  libraries	and  database  plugins are disabled at compile
       time, otherwise it typically defaults to	/usr/lib/postfix  or  /usr/lo-
       cal/lib/postfix.

       Notes:

       o      The directory specified with shlib_directory should contain only
	      Postfix-related files. Postfix dynamically-linked	libraries  and
	      database	plugins	 should	 not be	installed in a "public"	system
	      directory	such as	/usr/lib or  /usr/local/lib.  Linking  Postfix
	      dynamically-linked   library  files  or  database	 plugins  into
	      non-Postfix  programs  is	 not   supported.    Postfix   dynami-
	      cally-linked  libraries  and  database plugins implement a Post-
	      fix-internal API that changes without maintaining	compatibility.

       o      You can change the shlib_directory value after Postfix is	built.
	      However,	you  may have to run ldconfig or equivalent to prevent
	      Postfix programs from failing because the	libpostfix-*.so	 files
	      are  not	found.	 No ldconfig command is	needed if you keep the
	      libpostfix-*.so files in the compiled-in	default	 $shlib_direc-
	      tory location.

       This feature is available in Postfix 3.0	and later.

show_user_unknown_table_name (default: yes)
       Display	the  name  of  the  recipient  table in	the "User unknown" re-
       sponses.	 The extra detail makes	troubleshooting	easier	but  also  re-
       veals information that is nobody	else's business.

       This feature is available in Postfix 2.0	and later.

showq_service_name (default: showq)
       The name	of the showq(8)	service. This service produces mail queue sta-
       tus reports.

       This feature is available in Postfix 2.0	and later.

smtp_address_preference	(default: any)
       The address type	("ipv6", "ipv4"	or "any") that the Postfix SMTP	client
       will  try  first,  when	a destination has IPv6 and IPv4	addresses with
       equal MX	preference. This feature has no	effect unless the  inet_proto-
       cols setting enables both IPv4 and IPv6.

       Postfix	SMTP  client  address preference has evolved. With Postfix 2.8
       the default is "ipv6"; earlier implementations are hard-coded to	prefer
       IPv6 over IPv4.

       Notes for mail delivery between sites that have both IPv4 and IPv6 con-
       nectivity:

       o      The setting "smtp_address_preference = ipv6" is unsafe.  It  can
	      fail  to deliver mail when there is an outage that affects IPv6,
	      while the	destination is still reachable over IPv4.

       o      The setting "smtp_address_preference = any" is safe. With	 this,
	      mail  will  eventually  be  delivered even if there is an	outage
	      that affects IPv6	or IPv4, as long as it does not	affect both.

       This feature is available in Postfix 2.8	and later.

smtp_address_verify_target (default: rcpt)
       In the context of email address verification, the SMTP  protocol	 stage
       that  determines	 whether an email address is deliverable.  Specify one
       of "rcpt" or "data".  The latter	is needed  with	 remote	 SMTP  servers
       that  reject  recipients	 after the DATA	command. Use transport_maps to
       apply this feature selectively:

	   /usr/local/etc/postfix/main.cf:
	       transport_maps =	hash:$config_directory/transport

	   /usr/local/etc/postfix/transport:
	       smtp-domain-that-verifies-after-data    smtp-data-target:
	       lmtp-domain-that-verifies-after-data    lmtp-data-target:

	   /usr/local/etc/postfix/master.cf:
	       smtp-data-target	   unix	   -	-    n	  -    -    smtp
		   -o smtp_address_verify_target=data
	       lmtp-data-target	   unix	   -	-    n	  -    -    lmtp
		   -o lmtp_address_verify_target=data

       Unselective use of the "data" target does no harm, but will  result  in
       unnecessary  "lost  connection  after  DATA" events at remote SMTP/LMTP
       servers.

       This feature is available in Postfix 3.0	and later.

smtp_always_send_ehlo (default:	yes)
       Always send EHLO	at the start of	an SMTP	session.

       With "smtp_always_send_ehlo = no", the Postfix SMTP client  sends  EHLO
       only when the word "ESMTP" appears in the server	greeting banner	(exam-
       ple: 220	spike.porcupine.org ESMTP Postfix).

smtp_balance_inet_protocols (default: yes)
       When a remote destination resolves to a combination of  IPv4  and  IPv6
       addresses,  ensure  that	 the  Postfix SMTP client can try both address
       types before it runs into the smtp_mx_address_limit.

       This avoids an interoperability problem when a destination resolves  to
       primarily  IPv6	addresses,  the	 smtp_address_limit feature eliminates
       most or all IPv4	addresses, and the destination is not  reachable  over
       IPv6.

       This feature is available in Postfix 3.3	and later.

smtp_bind_address (default: empty)
       An  optional  numerical	network	 address  that the Postfix SMTP	client
       should bind to when making an IPv4 connection.

       This can	be specified in	the main.cf file for all SMTP clients,	or  it
       can be specified	in the master.cf file for a specific client, for exam-
       ple:

	   /usr/local/etc/postfix/master.cf:
	       smtp ...	smtp -o	smtp_bind_address=11.22.33.44

       See smtp_bind_address_enforce for  how  Postfix	should	handle	errors
       (Postfix	3.7 and	later).

       Note  1:	 when inet_interfaces specifies	no more	than one IPv4 address,
       and that	address	is a non-loopback address, it is automatically used as
       the  smtp_bind_address.	This supports virtual IP hosting, but can be a
       problem on multi-homed firewalls. See the inet_interfaces documentation
       for more	detail.

       Note 2: address information may be enclosed inside [], but this form is
       not required here.

smtp_bind_address6 (default: empty)
       An optional numerical network address  that  the	 Postfix  SMTP	client
       should bind to when making an IPv6 connection.

       This feature is available in Postfix 2.2	and later.

       This  can  be specified in the main.cf file for all SMTP	clients, or it
       can be specified	in the master.cf file for a specific client, for exam-
       ple:

	   /usr/local/etc/postfix/master.cf:
	       smtp ...	smtp -o	smtp_bind_address6=1:2:3:4:5:6:7:8

       See  smtp_bind_address_enforce  for  how	 Postfix  should handle	errors
       (Postfix	3.7 and	later).

       Note 1: when inet_interfaces specifies no more than one	IPv6  address,
       and that	address	is a non-loopback address, it is automatically used as
       the smtp_bind_address6.	This supports virtual IP hosting, but can be a
       problem on multi-homed firewalls. See the inet_interfaces documentation
       for more	detail.

       Note 2: address information may be enclosed inside [], but this form is
       not recommended here.

smtp_bind_address_enforce (default: no)
       Defer   delivery	  when	the  Postfix  SMTP  client  cannot  apply  the
       smtp_bind_address or smtp_bind_address6 setting.	By default, the	 Post-
       fix SMTP	client will continue delivery after logging a warning.

       This feature is available in Postfix 3.7	and later.

smtp_body_checks (default: empty)
       Restricted  body_checks(5)  tables  for the Postfix SMTP	client.	 These
       tables are searched while mail is being delivered.  Actions that	change
       the delivery time or destination	are not	available.

       This feature is available in Postfix 2.5	and later.

smtp_cname_overrides_servername	(default: version dependent)
       When  the remote	SMTP servername	is a DNS CNAME,	replace	the servername
       with the	result from CNAME expansion for	the purpose of	logging,  SASL
       password	lookup,	TLS policy decisions, or TLS certificate verification.
       The value "no" hardens Postfix smtp_tls_per_site	 hostname-based	 poli-
       cies against false hostname information in DNS CNAME records, and makes
       SASL password file lookups more predictable. This is the	 default  set-
       ting as of Postfix 2.3.

       When   DNS   CNAME  records  are	 validated  with  secure  DNS  lookups
       (smtp_dns_support_level = dnssec), they are always allowed to  override
       the above servername (Postfix 2.11 and later).

       This feature is available in Postfix 2.2.9 and later.

smtp_connect_timeout (default: 30s)
       The  Postfix SMTP client	time limit for completing a TCP	connection, or
       zero (use the operating system built-in time limit).

       When no connection can be made within the deadline,  the	 Postfix  SMTP
       client  tries the next address on the mail exchanger list. Specify 0 to
       disable the time	limit (i.e. use	whatever timeout is implemented	by the
       operating system).

       Specify	a  non-negative	time value (an integral	value plus an optional
       one-letter suffix that specifies	the time unit).	 Time units:  s	 (sec-
       onds),  m  (minutes), h (hours),	d (days), w (weeks).  The default time
       unit is s (seconds).

smtp_connection_cache_destinations (default: empty)
       Permanently enable SMTP connection caching for the  specified  destina-
       tions.	With SMTP connection caching, a	connection is not closed imme-
       diately after completion	of a mail transaction.	Instead,  the  connec-
       tion  is	kept open for up to $smtp_connection_cache_time_limit seconds.
       This allows connections to be reused for	other deliveries, and can  im-
       prove mail delivery performance.

       Specify	a  comma  or  white  space  separated  list of destinations or
       pseudo-destinations:

       o      if mail is sent  without	a  relay  host:	 a  domain  name  (the
	      right-hand side of an email address, without the [] around a nu-
	      meric IP address),

       o      if mail is sent via a relay host:	a relay	host name (without  []
	      or  non-default  TCP  port),  as	specified in main.cf or	in the
	      transport	map,

       o      if mail is sent via a UNIX-domain	socket:	 a  pathname  (without
	      the unix:	prefix),

       o      a	 /file/name  with  domain names	and/or relay host names	as de-
	      fined above,

       o      a	"type:table" with domain names and/or relay host names on  the
	      left-hand	 side.	 The  right-hand side result from "type:table"
	      lookups is ignored.

       This feature is available in Postfix 2.2	and later.

smtp_connection_cache_on_demand	(default: yes)
       Temporarily enable SMTP connection caching while	a  destination	has  a
       high volume of mail in the active queue.	 With SMTP connection caching,
       a connection is not closed  immediately	after  completion  of  a  mail
       transaction.  Instead, the connection is	kept open for up to $smtp_con-
       nection_cache_time_limit	seconds.  This allows connections to be	reused
       for other deliveries, and can improve mail delivery performance.

       This feature is available in Postfix 2.2	and later.

smtp_connection_cache_time_limit (default: 2s)
       When SMTP connection caching is enabled,	the amount of time that	an un-
       used SMTP client	socket is kept open before it is closed.  Do not spec-
       ify larger values without permission from the remote sites.

       This feature is available in Postfix 2.2	and later.

smtp_connection_reuse_count_limit (default: 0)
       When  SMTP  connection  caching is enabled, the number of times that an
       SMTP session may	be reused before it is closed,	or  zero  (no  limit).
       With a reuse count limit	of N, a	connection is used up to N+1 times.

       NOTE: This feature is unsafe. When a high-volume	destination has	multi-
       ple inbound MTAs, then the slowest inbound MTA will  attract  the  most
       connections  to	that destination.  This	limitation does	not exist with
       the smtp_connection_reuse_time_limit feature.

       This feature is available in Postfix 2.11.

smtp_connection_reuse_time_limit (default: 300s)
       The amount of time during which Postfix will use	an SMTP	connection re-
       peatedly.   The	timer starts when the connection is initiated (i.e. it
       includes	the connect, greeting and helo latency,	in addition to the la-
       tencies of subsequent mail delivery transactions).

       This feature addresses a	performance stability problem with remote SMTP
       servers.	This problem is	not specific to	Postfix: it  can  happen  when
       any  MTA	 sends large amounts of	SMTP email to a	site that has multiple
       MX hosts.

       The problem starts when one of a	set of MX hosts	 becomes  slower  than
       the  rest.   Even though	SMTP clients connect to	fast and slow MX hosts
       with equal probability, the slow	MX host	ends up	with more simultaneous
       inbound	connections than the faster MX hosts, because the slow MX host
       needs more time to serve	each client request.

       The slow	MX host	becomes	a connection attractor.	 If one	 MX  host  be-
       comes  N	times slower than the rest, it dominates mail delivery latency
       unless there are	more than N fast MX hosts to counter the  effect.  And
       if  the number of MX hosts is smaller than N, the mail delivery latency
       becomes effectively that	of the slowest MX host divided	by  the	 total
       number of MX hosts.

       The solution uses connection caching in a way that differs from Postfix
       version 2.2.  By	limiting the amount of time during which a  connection
       can  be	used  repeatedly (instead of limiting the number of deliveries
       over that connection), Postfix not only restores	fairness in  the  dis-
       tribution of simultaneous connections across a set of MX	hosts, it also
       favors deliveries over connections that perform well, which is  exactly
       what we want.

       The  default  reuse time	limit, 300s, is	comparable to the various smtp
       transaction timeouts which are fair estimates of	maximum	excess latency
       for  a slow delivery.  Note that	hosts may accept thousands of messages
       over a single connection	 within	 the  default  connection  reuse  time
       limit.  This number is much larger than the default Postfix version 2.2
       limit of	10 messages per	cached connection. It may prove	 necessary  to
       lower the limit to avoid	interoperability issues	with MTAs that exhibit
       bugs when many messages are delivered via a single connection.  A lower
       reuse  time limit risks losing the benefit of connection	reuse when the
       average connection and mail delivery latency  exceeds  the  reuse  time
       limit.

       This feature is available in Postfix 2.3	and later.

smtp_data_done_timeout (default: 600s)
       The  Postfix  SMTP  client time limit for sending the SMTP ".", and for
       receiving the remote SMTP server	response.

       When no response	is received within the deadline, a warning  is	logged
       that the	mail may be delivered multiple times.

       Specify	a  non-zero  time  value  (an  integral	value plus an optional
       one-letter suffix that specifies	the time unit).	 Time units:  s	 (sec-
       onds),  m  (minutes), h (hours),	d (days), w (weeks).  The default time
       unit is s (seconds).

smtp_data_init_timeout (default: 120s)
       The Postfix SMTP	client time limit for sending the SMTP	DATA  command,
       and for receiving the remote SMTP server	response.

       Time  units:  s (seconds), m (minutes), h (hours), d (days), w (weeks).
       The default time	unit is	s (seconds).

smtp_data_xfer_timeout (default: 180s)
       The Postfix SMTP	client time limit for sending the  SMTP	 message  con-
       tent.	When   the   connection	  makes	 no  progress  for  more  than
       $smtp_data_xfer_timeout seconds the Postfix SMTP	client terminates  the
       transfer.

       Time  units:  s (seconds), m (minutes), h (hours), d (days), w (weeks).
       The default time	unit is	s (seconds).

smtp_defer_if_no_mx_address_found (default: no)
       Defer mail delivery when	no MX record resolves to an IP address.

       The default (no)	is to return the mail  as  undeliverable.  With	 older
       Postfix versions	the default was	to keep	trying to deliver the mail un-
       til someone fixed the MX	record or until	the mail was too old.

       Note: the Postfix SMTP client always ignores MX records with  equal  or
       worse preference	than the local MTA itself.

       This feature is available in Postfix 2.1	and later.

smtp_delivery_status_filter (default: $default_delivery_status_filter)
       Optional	 filter	 for the smtp(8) delivery agent	to change the delivery
       status code or explanatory text of successful or	unsuccessful  deliver-
       ies.  See default_delivery_status_filter	for details.

       NOTE: This feature modifies Postfix SMTP	client error or	non-error mes-
       sages that may or may not be derived from remote	SMTP server responses.
       In  contrast, the smtp_reply_filter feature modifies remote SMTP	server
       responses only.

smtp_destination_concurrency_limit   (default:	  $default_destination_concur-
       rency_limit)
       The  maximal  number of parallel	deliveries to the same destination via
       the smtp	message	delivery transport. This  limit	 is  enforced  by  the
       queue  manager.	The message delivery transport name is the first field
       in the entry in the master.cf file.

smtp_destination_recipient_limit    (default:	  $default_destination_recipi-
       ent_limit)
       The  maximal  number of recipients per message for the smtp message de-
       livery transport. This limit is enforced	by the queue manager. The mes-
       sage  delivery  transport  name	is the first field in the entry	in the
       master.cf file.

       Setting this parameter to a value of 1 changes the meaning of smtp_des-
       tination_concurrency_limit from concurrency per domain into concurrency
       per recipient.

smtp_discard_ehlo_keyword_address_maps (default: empty)
       Lookup tables, indexed by the remote SMTP server	address, with case in-
       sensitive  lists	 of  EHLO  keywords (pipelining, starttls, auth, etc.)
       that the	Postfix	SMTP client will ignore	in the EHLO  response  from  a
       remote SMTP server. See smtp_discard_ehlo_keywords for details. The ta-
       ble  is	not  indexed  by  hostname  for	 consistency  with  smtpd_dis-
       card_ehlo_keyword_address_maps.

       Specify zero or more "type:name"	lookup tables, separated by whitespace
       or comma. Tables	will be	searched in the	specified order	until a	 match
       is found.

       This feature is available in Postfix 2.2	and later.

smtp_discard_ehlo_keywords (default: empty)
       A  case	insensitive list of EHLO keywords (pipelining, starttls, auth,
       etc.) that the Postfix SMTP client will ignore  in  the	EHLO  response
       from a remote SMTP server.

       This feature is available in Postfix 2.2	and later.

       Notes:

       o      Specify the silent-discard pseudo	keyword	to prevent this	action
	      from being logged.

       o      Use the smtp_discard_ehlo_keyword_address_maps feature  to  dis-
	      card EHLO	keywords selectively.

smtp_dns_reply_filter (default:	empty)
       Optional	 filter	 for  Postfix SMTP client DNS lookup results.  Specify
       zero or more lookup tables.  The	lookup	tables	are  searched  in  the
       given  order  for  a match with the DNS lookup result, converted	to the
       following form:

	   name	ttl class type preference value

       The class field is always "IN", the preference field exists only	for MX
       records,	the names of hosts, domains, etc.  end in ".", and those names
       are in ASCII form (xn--mumble form in the case of UTF8 names).

       When a match is found, the table	lookup result specifies	an action.  By
       default,	 the  table  query  and	 the action name are case-insensitive.
       Currently, only the IGNORE action is implemented.

       Notes:

       o      Postfix DNS reply	filters	have no	effect on implicit DNS lookups
	      through nsswitch.conf or equivalent mechanisms.

       o      The  Postfix  SMTP/LMTP  client  uses  smtp_dns_reply_filter and
	      lmtp_dns_reply_filter only to discover a	remote	SMTP  or  LMTP
	      service (record types MX,	A, AAAA, and TLSA).  These lookups are
	      also made	to implement the features reject_unverified_sender and
	      reject_unverified_recipient.

       o      The  Postfix SMTP/LMTP client defers mail	delivery when a	filter
	      removes all lookup results from a	successful query.

       o      Postfix SMTP server uses smtpd_dns_reply_filter only to look  up
	      MX,  A,  AAAA,  and  TXT	records	 to implement the features re-
	      ject_unknown_helo_hostname,  reject_unknown_sender_domain,   re-
	      ject_unknown_recipient_domain, reject_rbl_*, and reject_rhsbl_*.

       o      The  Postfix  SMTP server	logs a warning or defers mail delivery
	      when a filter removes  all  lookup  results  from	 a  successful
	      query.

       Example:	ignore Google AAAA records in Postfix SMTP client DNS lookups,
       because Google sometimes	hard-rejects mail from IPv6 clients with valid
       PTR etc.	records.

       /usr/local/etc/postfix/main.cf:
	   smtp_dns_reply_filter = pcre:$config_directory/smtp_dns_reply_filter

       /usr/local/etc/postfix/smtp_dns_reply_filter:
	   # /domain ttl IN AAAA address/ action, all case-insensitive.
	   # Note: the domain name ends	in ".".
	   /^\S+\.google\.com\.\s+\S+\s+\S+\s+AAAA\s+/ IGNORE

       This feature is available in Postfix 3.0	and later.

smtp_dns_resolver_options (default: empty)
       DNS Resolver options for	the Postfix SMTP client.  Specify zero or more
       of the following	options, separated by  comma  or  whitespace.	Option
       names  are  case-sensitive. Some	options	refer to domain	names that are
       specified in the	file /etc/resolv.conf or equivalent.

       res_defnames
	      Append the current domain	name to	single-component names	(those
	      that do not contain a "."	character). This can produce incorrect
	      results, and is the hard-coded behavior prior to Postfix 2.8.

       res_dnsrch
	      Search for host names in the current domain and  in  parent  do-
	      mains.  This  can	produce	incorrect results and is therefore not
	      recommended.

       This feature is available in Postfix 2.8	and later.

smtp_dns_support_level (default: empty)
       Level of	DNS support in the Postfix SMTP	client.	  With	"smtp_dns_sup-
       port_level"   left  at  its  empty  default  value,  the	 legacy	 "dis-
       able_dns_lookups" parameter controls whether  DNS  is  enabled  in  the
       Postfix SMTP client, otherwise the legacy parameter is ignored.

       Specify one of the following:

       disabled
	      Disable  DNS  lookups.  No MX lookups are	performed and hostname
	      to address lookups are unconditionally "native".	 This  setting
	      is not appropriate for hosts that	deliver	mail to	the public In-
	      ternet.  Some obsolete how-to documents recommend	disabling  DNS
	      lookups in some configurations with content_filters.  This is no
	      longer required and strongly discouraged.

       enabled
	      Enable DNS lookups.  Nexthop destination domains not enclosed in
	      "[]"  will  be subject to	MX lookups.  If	"dns" and "native" are
	      included in the "smtp_host_lookup" parameter value, DNS will  be
	      queried first to resolve MX-host A records, followed by "native"
	      lookups if no answer is found in DNS.

       dnssec Enable DNSSEC lookups.  The "dnssec" setting  differs  from  the
	      "enabled"	setting	above in the following ways:

       o      Any  MX lookups will set RES_USE_DNSSEC and RES_USE_EDNS0	to re-
	      quest  DNSSEC-validated  responses.  If  the  MX	 response   is
	      DNSSEC-validated the corresponding hostnames are considered val-
	      idated.

       o      The address lookups of validated hostnames are  also  validated,
	      (provided	 of  course "smtp_host_lookup" includes	"dns", see be-
	      low).

       o      Temporary	failures in DNSSEC-enabled hostname-to-address resolu-
	      tion  block  any	"native" lookups.  Additional "native" lookups
	      only happen when DNSSEC lookups hard-fail	(NODATA	or NXDOMAIN).

       The  Postfix  SMTP  client  considers  non-MX  "[nexthop]"  and	"[nex-
       thop]:port"  destinations equivalent to statically-validated MX records
       of the form "nexthop.  IN MX 0 nexthop."	 Therefore, with "dnssec" sup-
       port turned on, validated hostname-to-address lookups apply to the nex-
       thop domain of any "[nexthop]" or "[nexthop]:port"  destination.	  This
       is also true for	LMTP "inet:host" and "inet:host:port" destinations, as
       LMTP hostnames are never	subject	to MX lookups.

       The "dnssec" setting is recommended only	if you plan to use the dane or
       dane-only  TLS  security	 level,	 otherwise  enabling DNSSEC support in
       Postfix offers no additional security.  Postfix DNSSEC  support	relies
       on  an  upstream	recursive nameserver that validates DNSSEC signatures.
       Such a DNS server will always filter out	 forged	 DNS  responses,  even
       when Postfix itself is not configured to	use DNSSEC.

       When using Postfix DANE support the "smtp_host_lookup" parameter	should
       include "dns", as DANE is not applicable	to hosts resolved via "native"
       lookups.

       As  mentioned  above, Postfix is	not a validating stub resolver;	it re-
       lies on the system's configured DNSSEC-validating recursive  nameserver
       to perform all DNSSEC validation.  Since	this nameserver's DNSSEC-vali-
       dated responses will be fully trusted, it is strongly recommended  that
       the  MTA	 host  have  a local DNSSEC-validating recursive caching name-
       server listening	on a loopback address, and be configured to  use  only
       this nameserver for all lookups.	 Otherwise, Postfix may	remain subject
       to man-in-the-middle attacks that forge responses  from	the  recursive
       nameserver

       DNSSEC support requires a version of Postfix compiled against a reason-
       ably-modern DNS resolver(3) library that	implements the	RES_USE_DNSSEC
       and RES_USE_EDNS0 resolver options.

       This feature is available in Postfix 2.11 and later.

smtp_enforce_tls (default: no)
       Enforcement  mode: require that remote SMTP servers use TLS encryption,
       and never send mail in the clear.  This also requires that  the	remote
       SMTP  server hostname matches the information in	the remote server cer-
       tificate, and that the remote SMTP server certificate was issued	 by  a
       CA  that	 is  trusted  by  the  Postfix SMTP client. If the certificate
       doesn't verify or the hostname doesn't match, delivery is deferred  and
       mail stays in the queue.

       The  server  hostname is	matched	against	all names provided as dNSNames
       in the SubjectAlternativeName.  If no dNSNames are specified, the  Com-
       monName	is checked.  The behavior may be changed with the smtp_tls_en-
       force_peername option.

       This option is useful only if you are definitely	 sure  that  you  will
       only  connect to	servers	that support RFC 2487 _and_ that provide valid
       server certificates.  Typical use is for	clients	that  send  all	 their
       email to	a dedicated mailhub.

       This  feature  is  available in Postfix 2.2 and later. With Postfix 2.3
       and later use smtp_tls_security_level instead.

smtp_fallback_relay (default: $fallback_relay)
       Optional	list of	relay hosts for	SMTP destinations that can't be	 found
       or that are unreachable.	With Postfix 2.2 and earlier this parameter is
       called fallback_relay.

       By default, mail	is returned to the sender when a  destination  is  not
       found, and delivery is deferred when a destination is unreachable.

       With  bulk  email  deliveries, it can be	beneficial to run the fallback
       relay MTA on the	same host, so that it can reuse	the sender IP address.
       This  speeds up deliveries that are delayed by IP-based reputation sys-
       tems (greylist, etc.).

       The fallback relays must	be SMTP	destinations. Specify a	domain,	 host,
       host:port,  [host]:port,	 [address]  or [address]:port; the form	[host]
       turns off MX lookups.  If you specify multiple SMTP destinations, Post-
       fix will	try them in the	specified order.

       To  prevent  mailer loops between MX hosts and fall-back	hosts, Postfix
       version 2.2 and later will not use the fallback relays for destinations
       that it is MX host for (assuming	DNS lookup is turned on).

smtp_generic_maps (default: empty)
       Optional	 lookup	 tables	 that perform address rewriting	in the Postfix
       SMTP client, typically to transform a  locally  valid  address  into  a
       globally	 valid address when sending mail across	the Internet.  This is
       needed when the local machine does not have  its	 own  Internet	domain
       name, but uses something	like localdomain.local instead.

       Specify zero or more "type:name"	lookup tables, separated by whitespace
       or comma. Tables	will be	searched in the	specified order	until a	 match
       is found.

       The table format	and lookups are	documented in generic(5); examples are
       shown in	the ADDRESS_REWRITING_README and STANDARD_CONFIGURATION_README
       documents.

       This feature is available in Postfix 2.2	and later.

smtp_header_checks (default: empty)
       Restricted  header_checks(5) tables for the Postfix SMTP	client.	 These
       tables are searched while mail is being delivered.  Actions that	change
       the delivery time or destination	are not	available.

       This feature is available in Postfix 2.5	and later.

smtp_helo_name (default: $myhostname)
       The hostname to send in the SMTP	HELO or	EHLO command.

       The  default  value  is	the  machine  hostname.	 Specify a hostname or
       [ip.add.re.ss].

       This information	can be specified in the	 main.cf  file	for  all  SMTP
       clients,	 or  it	 can be	specified in the master.cf file	for a specific
       client, for example:

	   /usr/local/etc/postfix/master.cf:
	       mysmtp ... smtp -o smtp_helo_name=foo.bar.com

       This feature is available in Postfix 2.0	and later.

smtp_helo_timeout (default: 300s)
       The Postfix SMTP	client time limit for sending the HELO	or  EHLO  com-
       mand, and for receiving the initial remote SMTP server response.

       Specify	a  non-zero  time  value  (an  integral	value plus an optional
       one-letter suffix that specifies	the time unit).	 Time units:  s	 (sec-
       onds),  m  (minutes), h (hours),	d (days), w (weeks).  The default time
       unit is s (seconds).

smtp_host_lookup (default: dns)
       What mechanisms the Postfix SMTP	client uses to look up a host's	IP ad-
       dress.	This  parameter	is ignored when	DNS lookups are	disabled (see:
       disable_dns_lookups and smtp_dns_support_level).	 The  "dns"  mechanism
       is always tried before "native" if both are listed.

       Specify one of the following:

       dns    Hosts can	be found in the	DNS (preferred).

       native Use the native naming service only (nsswitch.conf, or equivalent
	      mechanism).

       dns, native
	      Use the native service for hosts not found in the	DNS.

       This feature is available in Postfix 2.1	and later.

smtp_line_length_limit (default: 998)
       The maximal length of message header and	body lines that	 Postfix  will
       send  via  SMTP.	This limit does	not include the	<CR><LF> at the	end of
       each line.  Longer lines	are broken by inserting	"<CR><LF><SPACE>",  to
       minimize	 the  damage  to  MIME formatted mail. Specify zero to disable
       this limit.

       The Postfix limit of 998	characters not including <CR><LF>  is  consis-
       tent  with  the	SMTP limit of 1000 characters including	<CR><LF>.  The
       Postfix limit was 990 with Postfix 2.8 and earlier.

smtp_mail_timeout (default: 300s)
       The Postfix SMTP	client time limit for sending the MAIL	FROM  command,
       and for receiving the remote SMTP server	response.

       Specify	a  non-zero  time  value  (an  integral	value plus an optional
       one-letter suffix that specifies	the time unit).	 Time units:  s	 (sec-
       onds),  m  (minutes), h (hours),	d (days), w (weeks).  The default time
       unit is s (seconds).

smtp_mime_header_checks	(default: empty)
       Restricted mime_header_checks(5)	tables for the	Postfix	 SMTP  client.
       These  tables are searched while	mail is	being delivered.  Actions that
       change the delivery time	or destination are not available.

       This feature is available in Postfix 2.5	and later.

smtp_min_data_rate (default: 500)
       The minimum plaintext data transfer rate	in bytes/second	for  DATA  re-
       quests, when deadlines are enabled with smtp_per_request_deadline.  Af-
       ter a write operation transfers N plaintext message bytes (possibly af-
       ter TLS encryption), and	after the DATA request deadline	is decremented
       by the elapsed time of that write operation, the	DATA request  deadline
       is  incremented by N/smtp_min_data_rate seconds.	 However, the deadline
       will  never  be	incremented  beyond  the  time	limit  specified  with
       smtp_data_xfer_timeout.

       This feature is available in Postfix 3.7	and later.

smtp_mx_address_limit (default:	5)
       The  maximal number of MX (mail exchanger) IP addresses that can	result
       from Postfix SMTP client	mail exchanger lookups,	or  zero  (no  limit).
       Prior to	Postfix	version	2.3, this limit	was disabled by	default.

       This feature is available in Postfix 2.1	and later.

smtp_mx_session_limit (default:	2)
       The  maximal  number  of	 SMTP sessions per delivery request before the
       Postfix SMTP client gives up or delivers	to a fall-back relay host,  or
       zero  (no  limit).  This	restriction ignores sessions that fail to com-
       plete the SMTP initial handshake	(Postfix version 2.2 and  earlier)  or
       that  fail  to complete the EHLO	and TLS	handshake (Postfix version 2.3
       and later).

       This feature is available in Postfix 2.1	and later.

smtp_nested_header_checks (default: empty)
       Restricted nested_header_checks(5) tables for the Postfix SMTP  client.
       These  tables are searched while	mail is	being delivered.  Actions that
       change the delivery time	or destination are not available.

       This feature is available in Postfix 2.5	and later.

smtp_never_send_ehlo (default: no)
       Never send EHLO at the start of an SMTP session.	See also the  smtp_al-
       ways_send_ehlo parameter.

smtp_per_record_deadline (default: no)
       Change  the  behavior  of  the  smtp_*_timeout time limits, from	a time
       limit per read or write system call, to a time limit to send or receive
       a  complete record (an SMTP command line, SMTP response line, SMTP mes-
       sage content line, or TLS protocol message).  This  limits  the	impact
       from hostile peers that trickle data one	byte at	a time.

       Note:  when per-record deadlines	are enabled, a short timeout may cause
       problems	with TLS over very slow	network	connections.  The reasons  are
       that  a	TLS protocol message can be up to 16 kbytes long (with TLSv1),
       and that	an entire TLS protocol message must be sent or received	within
       the per-record deadline.

       This  feature  is  available in Postfix 2.9-3.6.	With older Postfix re-
       leases, the behavior is as if this parameter is set  to	"no".  Postfix
       3.7 and later use smtp_per_request_deadline.

smtp_per_request_deadline (default: no)
       Change  the  behavior  of  the  smtp_*_timeout time limits, from	a time
       limit per plaintext or TLS read or write	call, to a combined time limit
       for  sending  a complete	SMTP request and for receiving a complete SMTP
       response. The deadline limits only the time spent waiting for plaintext
       or  TLS	read or	write calls, not time spent elsewhere. The per-request
       deadline	limits the impact from hostile peers  that  trickle  data  one
       byte at a time.

       See smtp_min_data_rate for how the per-request deadline is managed dur-
       ing the DATA phase.

       Note: when per-request deadlines	are enabled, a short  time  limit  may
       cause  problems with TLS	over very slow network connections. The	reason
       is that a TLS protocol message can  be  up  to  16  kbytes  long	 (with
       TLSv1),	and  that  an  entire TLS protocol message must	be transferred
       within the per-request deadline.

       This feature is available in Postfix 3.7	and later. A  weaker  feature,
       called smtp_per_record_deadline,	is available with Postfix 2.9-3.6.

       This feature is available in Postfix 3.7	and later.

smtp_pix_workaround_delay_time (default: 10s)
       How  long  the Postfix SMTP client pauses before	sending	".<CR><LF>" in
       order to	work around the	PIX firewall "<CR><LF>.<CR><LF>" bug.

       Choosing	too short a time makes this workaround ineffective when	 send-
       ing large messages over slow network connections.

       Specify	a  non-zero  time  value  (an  integral	value plus an optional
       one-letter suffix that specifies	the time unit).	 Time units:  s	 (sec-
       onds),  m  (minutes), h (hours),	d (days), w (weeks).  The default time
       unit is s (seconds).

smtp_pix_workaround_maps (default: empty)
       Lookup tables, indexed by the remote SMTP server	address, with per-des-
       tination	workarounds for	CISCO PIX firewall bugs.  The table is not in-
       dexed by	hostname for  consistency  with	 smtp_discard_ehlo_keyword_ad-
       dress_maps.

       Specify zero or more "type:name"	lookup tables, separated by whitespace
       or comma. Tables	will be	searched in the	specified order	until a	 match
       is found.

       This feature is available in Postfix 2.4	and later.

smtp_pix_workaround_threshold_time (default: 500s)
       How  long a message must	be queued before the Postfix SMTP client turns
       on the PIX firewall "<CR><LF>.<CR><LF>"	bug  workaround	 for  delivery
       through firewalls with "smtp fixup" mode	turned on.

       Specify	a  non-negative	time value (an integral	value plus an optional
       one-letter suffix that specifies	the time unit).	 Time units:  s	 (sec-
       onds),  m  (minutes), h (hours),	d (days), w (weeks).  The default time
       unit is s (seconds).

       By default, the workaround is turned off	for mail that  is  queued  for
       less  than  500	seconds.  In  other  words, the	workaround is normally
       turned off for the first	delivery attempt.

       Specify 0 to enable the PIX firewall "<CR><LF>.<CR><LF>"	bug workaround
       upon the	first delivery attempt.

smtp_pix_workarounds (default: disable_esmtp, delay_dotcrlf)
       A  list	that specifies zero or more workarounds	for CISCO PIX firewall
       bugs. These workarounds are implemented by  the	Postfix	 SMTP  client.
       Workaround names	are separated by comma or space, and are case insensi-
       tive.  This parameter setting can  be  overruled	 with  per-destination
       smtp_pix_workaround_maps	settings.

       delay_dotcrlf
	      Insert  a	 delay before sending ".<CR><LF>" after	the end	of the
	      message content.	The delay is  subject  to  the	smtp_pix_work-
	      around_delay_time	and smtp_pix_workaround_threshold_time parame-
	      ter settings.

       disable_esmtp
	      Disable all extended SMTP	commands: send HELO instead of EHLO.

       This feature is available in Postfix 2.4	and later.  The	 default  set-
       tings are backwards compatible with earlier Postfix versions.

smtp_quit_timeout (default: 300s)
       The  Postfix  SMTP  client time limit for sending the QUIT command, and
       for receiving the remote	SMTP server response.

       Specify a non-zero time value  (an  integral  value  plus  an  optional
       one-letter  suffix  that	specifies the time unit).  Time	units: s (sec-
       onds), m	(minutes), h (hours), d	(days),	w (weeks).  The	 default  time
       unit is s (seconds).

smtp_quote_rfc821_envelope (default: yes)
       Quote  addresses	 in Postfix SMTP client	MAIL FROM and RCPT TO commands
       as required by RFC 5321.	This includes putting quotes around an address
       localpart that ends in ".".

       The  default  is	to comply with RFC 5321. If you	have to	send mail to a
       broken SMTP server, configure a special SMTP client in master.cf:

	   /usr/local/etc/postfix/master.cf:
	       broken-smtp . . . smtp -o smtp_quote_rfc821_envelope=no

       and route mail for the destination in  question	to  the	 "broken-smtp"
       message delivery	with a transport(5) table.

       This feature is available in Postfix 2.1	and later.

smtp_randomize_addresses (default: yes)
       Randomize  the  order of	equal-preference MX host addresses.  This is a
       performance feature of the Postfix SMTP client.

smtp_rcpt_timeout (default: 300s)
       The Postfix SMTP	client time limit for sending the SMTP	RCPT  TO  com-
       mand, and for receiving the remote SMTP server response.

       Specify	a  non-zero  time  value  (an  integral	value plus an optional
       one-letter suffix that specifies	the time unit).	 Time units:  s	 (sec-
       onds),  m  (minutes), h (hours),	d (days), w (weeks).  The default time
       unit is s (seconds).

smtp_reply_filter (default: empty)
       A mechanism to transform	replies	from remote SMTP servers one line at a
       time.   This  is	 a last-resort tool to work around server replies that
       break interoperability with the Postfix SMTP client.   Other  uses  in-
       volve fault injection to	test Postfix's handling	of invalid responses.

       Notes:

       o      In  the case of a	multi-line reply, the Postfix SMTP client uses
	      the final	reply line's numerical SMTP reply  code	 and  enhanced
	      status code.

       o      The  numerical  SMTP  reply code (XYZ) takes precedence over the
	      enhanced status code (X.Y.Z).  When  the	enhanced  status  code
	      initial digit differs from the SMTP reply	code initial digit, or
	      when no enhanced status code is present, the Postfix SMTP	client
	      uses a generic enhanced status code (X.0.0) instead.

       Specify the name	of a "type:table" lookup table.	The search string is a
       single SMTP reply line as received from the remote SMTP server,	except
       that  the trailing <CR><LF> are removed.	 When the lookup succeeds, the
       result replaces the single SMTP reply line.

       Examples:

       /usr/local/etc/postfix/main.cf:
	   smtp_reply_filter = pcre:$config_directory/reply_filter

       /usr/local/etc/postfix/reply_filter:
	   # Transform garbage into "250-filler..." so that it looks like
	   # one line from a multi-line	reply. It does not matter what we
	   # substitute	here as	long it	has the	right syntax.  The Postfix
	   # SMTP client will use the final line's numerical SMTP reply
	   # code and enhanced status code.
	   !/^([2-5][0-9][0-9]($|[- ]))/ 250-filler for	garbage

       This feature is available in Postfix 2.7.

smtp_rset_timeout (default: 20s)
       The Postfix SMTP	client time limit for sending the  RSET	 command,  and
       for  receiving  the  remote SMTP	server response. The SMTP client sends
       RSET in order to	finish a recipient address probe, or to	verify that  a
       cached session is still usable.

       Specify	a  non-zero  time  value  (an  integral	value plus an optional
       one-letter suffix that specifies	the time unit).	 Time units:  s	 (sec-
       onds),  m  (minutes), h (hours),	d (days), w (weeks).  The default time
       unit is s (seconds).

       This feature is available in Postfix 2.1	and later.

smtp_sasl_auth_cache_name (default: empty)
       An optional table to prevent repeated SASL authentication failures with
       the same	remote SMTP server hostname, username and password. Each table
       (key, value) pair contains a server name, a username and	password,  and
       the full	server response. This information is stored when a remote SMTP
       server rejects an authentication	attempt	with a	535  reply  code.   As
       long as the smtp_sasl_password_maps information does not	change,	and as
       long as the smtp_sasl_auth_cache_name information does not expire  (see
       smtp_sasl_auth_cache_time)  the Postfix SMTP client avoids SASL authen-
       tication	attempts with the same server, username	and password, and  in-
       stead	bounces	   or	 defers	   mail	  as   controlled   with   the
       smtp_sasl_auth_soft_bounce configuration	parameter.

       Use  a  per-destination	delivery  concurrency  of  1   (for   example,
       "smtp_destination_concurrency_limit  =  1",  "relay_destination_concur-
       rency_limit = 1", etc.),	otherwise multiple delivery agents may experi-
       ence a login failure at the same	time.

       The  table  must	 be  accessed via the proxywrite service, i.e. the map
       name must start with "proxy:". The table	should be stored under the di-
       rectory specified with the data_directory parameter.

       This  feature  uses  cryptographic  hashing to protect plain-text pass-
       words, and requires that	Postfix	is compiled with TLS support.

       Example:

       smtp_sasl_auth_cache_name = proxy:btree:/var/lib/postfix/sasl_auth_cache

       This feature is available in Postfix 2.5	and later.

smtp_sasl_auth_cache_time (default: 90d)
       The maximal age of an smtp_sasl_auth_cache_name entry before it is  re-
       moved.

       Specify	a  non-negative	time value (an integral	value plus an optional
       one-letter suffix that specifies	the time unit).	 Time units:  s	 (sec-
       onds),  m  (minutes), h (hours),	d (days), w (weeks).  The default time
       unit is d (days).

       This feature is available in Postfix 2.5	and later.

smtp_sasl_auth_enable (default:	no)
       Enable SASL authentication in the Postfix SMTP client.  By default, the
       Postfix SMTP client uses	no authentication.

       Example:

       smtp_sasl_auth_enable = yes

smtp_sasl_auth_soft_bounce (default: yes)
       When  a remote SMTP server rejects a SASL authentication	request	with a
       535 reply code, defer mail delivery instead of returning	mail as	 unde-
       liverable.  The latter behavior was hard-coded prior to Postfix version
       2.5.

       Note: the setting "yes" overrides the global soft_bounce	parameter, but
       the setting "no"	does not.

       Example:

       # Default as of Postfix 2.5
       smtp_sasl_auth_soft_bounce = yes
       # The old hard-coded default
       smtp_sasl_auth_soft_bounce = no

       This feature is available in Postfix 2.5	and later.

smtp_sasl_mechanism_filter (default: empty)
       If non-empty, a Postfix SMTP client filter for the remote SMTP server's
       list of offered SASL mechanisms.	 Different client and server implemen-
       tations	may support different mechanism	lists; by default, the Postfix
       SMTP client will	use the	 intersection  of  the	two.  smtp_sasl_mecha-
       nism_filter  specifies  an  optional  third mechanism list to intersect
       with.

       Specify mechanism names,	"/file/name" patterns or  "type:table"	lookup
       tables.	The  right-hand	 side  result from "type:table"	lookups	is ig-
       nored. Specify "!pattern" to exclude a mechanism	name  from  the	 list.
       The  form  "!/file/name"	 is  supported only in Postfix version 2.4 and
       later.

       This feature is available in Postfix 2.2	and later.

       Examples:

       smtp_sasl_mechanism_filter = plain, login
       smtp_sasl_mechanism_filter = $config_directory/smtp_mechs
       smtp_sasl_mechanism_filter = !gssapi, !login, static:rest

smtp_sasl_password_maps	(default: empty)
       Optional	Postfix	SMTP client lookup tables with	one  username:password
       entry per sender, remote	hostname or next-hop domain. Per-sender	lookup
       is done only when sender-dependent authentication is  enabled.	If  no
       username:password entry is found, then the Postfix SMTP client will not
       attempt to authenticate to the remote host.

       The Postfix SMTP	client opens the lookup	table before going  to	chroot
       jail, so	you can	leave the password file	in /usr/local/etc/postfix.

       Specify zero or more "type:name"	lookup tables, separated by whitespace
       or comma. Tables	will be	searched in the	specified order	until a	 match
       is found.

smtp_sasl_path (default: empty)
       Implementation-specific information that	the Postfix SMTP client	passes
       through to the  SASL  plug-in  implementation  that  is	selected  with
       smtp_sasl_type.	 Typically  this specifies the name of a configuration
       file or rendezvous point.

       This feature is available in Postfix 2.3	and later.

smtp_sasl_security_options (default: noplaintext, noanonymous)
       Postfix SMTP client SASL	security options; as of	Postfix	2.3  the  list
       of available features depends on	the SASL client	implementation that is
       selected	with smtp_sasl_type.

       The following security features are defined for the cyrus  client  SASL
       implementation:

       Specify zero or more of the following:

       noplaintext
	      Disallow methods that use	plaintext passwords.

       noactive
	      Disallow methods subject to active (non-dictionary) attack.

       nodictionary
	      Disallow methods subject to passive (dictionary) attack.

       noanonymous
	      Disallow methods that allow anonymous authentication.

       mutual_auth
	      Only  allow  methods  that  provide  mutual  authentication (not
	      available	with SASL version 1).

       Example:

       smtp_sasl_security_options = noplaintext

smtp_sasl_tls_security_options (default: $smtp_sasl_security_options)
       The SASL	authentication security	options	that the Postfix  SMTP	client
       uses for	TLS encrypted SMTP sessions.

       This feature is available in Postfix 2.2	and later.

smtp_sasl_tls_verified_security_options	 (default: $smtp_sasl_tls_security_op-
       tions)
       The SASL	authentication security	options	that the Postfix  SMTP	client
       uses  for  TLS  encrypted SMTP sessions with a verified server certifi-
       cate.

       When mail is sent to the	public MX host	for  the  recipient's  domain,
       server certificates are by default optional, and	delivery proceeds even
       if certificate verification fails. For delivery via a  submission  ser-
       vice  that  requires SASL authentication, it may	be appropriate to send
       plaintext passwords only	when the connection to the server is  strongly
       encrypted and the server	identity is verified.

       The smtp_sasl_tls_verified_security_options parameter makes it possible
       to only enable plaintext	mechanisms when	a  secure  connection  to  the
       server is available. Submission servers subject to this policy must ei-
       ther have verifiable certificates or offer suitable non-plaintext  SASL
       mechanisms.

       This feature is available in Postfix 2.6	and later.

smtp_sasl_type (default: cyrus)
       The  SASL  plug-in type that the	Postfix	SMTP client should use for au-
       thentication.  The available types are listed with  the	"postconf  -A"
       command.

       This feature is available in Postfix 2.3	and later.

smtp_send_dummy_mail_auth (default: no)
       Whether	or not to append the "AUTH=<>" option to the MAIL FROM command
       in SASL-authenticated SMTP sessions. The	default	is not to  send	 this,
       to  avoid problems with broken remote SMTP servers.  Before Postfix 2.9
       the behavior is as if "smtp_send_dummy_mail_auth	= yes".

       This feature is available in Postfix 2.9	and later.

smtp_send_xforward_command (default: no)
       Send the	non-standard XFORWARD command when  the	 Postfix  SMTP	server
       EHLO response announces XFORWARD	support.

       This allows a Postfix SMTP delivery agent, used for injecting mail into
       a content filter, to forward the	name, address, protocol	and HELO  name
       of  the	original  client  to the content filter	and downstream queuing
       SMTP  server.  This  can	 produce  more	useful	logging	 than	local-
       host[127.0.0.1] etc.

       This feature is available in Postfix 2.1	and later.

smtp_sender_dependent_authentication (default: no)
       Enable sender-dependent authentication in the Postfix SMTP client; this
       is available only with SASL authentication, and disables	 SMTP  connec-
       tion  caching  to  ensure that mail from	different senders will use the
       appropriate credentials.

       This feature is available in Postfix 2.3	and later.

smtp_skip_4xx_greeting (default: yes)
       Skip SMTP servers that greet with a 4XX status code (go away, try again
       later).

       By  default,  the Postfix SMTP client moves on the next mail exchanger.
       Specify "smtp_skip_4xx_greeting = no" if	Postfix	should defer  delivery
       immediately.

       This  feature  is  available in Postfix 2.0 and earlier.	 Later Postfix
       versions	always skip remote SMTP	servers	that greet with	a  4XX	status
       code.

smtp_skip_5xx_greeting (default: yes)
       Skip remote SMTP	servers	that greet with	a 5XX status code.

       By  default,  the Postfix SMTP client moves on the next mail exchanger.
       Specify "smtp_skip_5xx_greeting = no" if	Postfix	should bounce the mail
       immediately.  Caution:  the  latter  behavior appears to	contradict RFC
       2821.

smtp_skip_quit_response	(default: yes)
       Do not wait for the response to the SMTP	QUIT command.

smtp_starttls_timeout (default:	300s)
       Time limit for Postfix SMTP client write	and read operations during TLS
       startup and shutdown handshake procedures.

       Specify	a  non-zero  time  value  (an  integral	value plus an optional
       one-letter suffix that specifies	the time unit).	 Time units:  s	 (sec-
       onds),  m  (minutes), h (hours),	d (days), w (weeks).  The default time
       unit is s (seconds).

       This feature is available in Postfix 2.2	and later.

smtp_tcp_port (default:	smtp)
       The default TCP port that the Postfix SMTP client connects to.  Specify
       a symbolic name (see services(5)) or a numeric port.

smtp_tls_CAfile	(default: empty)
       A  file	containing  CA certificates of root CAs	trusted	to sign	either
       remote SMTP server certificates or intermediate CA certificates.	 These
       are  loaded  into  memory  before  the smtp(8) client enters the	chroot
       jail.  If  the  number  of  trusted  roots  is  large,  consider	 using
       smtp_tls_CApath	instead,  but  note  that the latter directory must be
       present in the chroot jail if the smtp(8) client	is chrooted. This file
       may  also be used to augment the	client certificate trust chain,	but it
       is  best	 to  include  all  the	required  certificates	 directly   in
       $smtp_tls_cert_file (or,	Postfix	>= 3.4 $smtp_tls_chain_files).

       Specify	"smtp_tls_CAfile  =  /path/to/system_CA_file"  to use ONLY the
       system-supplied default Certification Authority certificates.

       Specify "tls_append_default_CA =	no" to prevent Postfix from  appending
       the system-supplied default CAs and trusting third-party	certificates.

       Example:

       smtp_tls_CAfile = $config_directory/CAcert.pem

       This feature is available in Postfix 2.2	and later.

smtp_tls_CApath	(default: empty)
       Directory with PEM format Certification Authority certificates that the
       Postfix SMTP client uses	to verify a remote  SMTP  server  certificate.
       Don't  forget  to  create the necessary "hash" links with, for example,
       "$OPENSSL_HOME/bin/c_rehash /usr/local/etc/postfix/certs".

       To use this option in chroot mode, this directory (or a copy)  must  be
       inside the chroot jail.

       Specify	"smtp_tls_CApath  =  /path/to/system_CA_directory" to use ONLY
       the system-supplied default Certification Authority certificates.

       Specify "tls_append_default_CA =	no" to prevent Postfix from  appending
       the system-supplied default CAs and trusting third-party	certificates.

       Example:

       smtp_tls_CApath = $config_directory/certs

       This feature is available in Postfix 2.2	and later.

smtp_tls_block_early_mail_reply	(default: no)
       Try  to detect a	mail hijacking attack based on a TLS protocol vulnera-
       bility (CVE-2009-3555), where  an  attacker  prepends  malicious	 HELO,
       MAIL,  RCPT,  DATA  commands to a Postfix SMTP client TLS session.  The
       attack would succeed with non-Postfix SMTP servers that	reply  to  the
       malicious HELO, MAIL, RCPT, DATA	commands after negotiating the Postfix
       SMTP client TLS session.

       This feature is available in Postfix 2.7.

smtp_tls_cert_file (default: empty)
       File with the Postfix SMTP client RSA certificate in PEM	format.	  This
       file  may  also	contain	 the  Postfix SMTP client private RSA key, and
       these may be the	same as	the Postfix SMTP server	 RSA  certificate  and
       key  file.   With  Postfix >= 3.4 the preferred way to configure	client
       keys and	certificates is	via the	"smtp_tls_chain_files" parameter.

       Do not configure	client certificates unless you must present client TLS
       certificates  to	 one or	more servers. Client certificates are not usu-
       ally needed, and	can cause problems in configurations  that  work  well
       without them. The recommended setting is	to let the defaults stand:

	   smtp_tls_cert_file =
	   smtp_tls_key_file =
	   smtp_tls_eccert_file	=
	   smtp_tls_eckey_file =
	   # Obsolete DSA parameters
	   smtp_tls_dcert_file =
	   smtp_tls_dkey_file =
	   # Postfix >=	3.4 interface
	   smtp_tls_chain_files	=

       The  best  way  to use the default settings is to comment out the above
       parameters in main.cf if	present.

       To enable remote	SMTP servers to	verify the Postfix  SMTP  client  cer-
       tificate,  the  issuing	CA  certificates must be made available	to the
       server. You should include the required certificates in the client cer-
       tificate	 file,	the  client  certificate first,	then the issuing CA(s)
       (bottom-up order).

       Example:	the certificate	for "client.example.com" was issued by "inter-
       mediate CA" which itself	has a certificate issued by "root CA".	As the
       "root" super-user create	the client.pem file with:

	   # umask 077
	   # cat client_key.pem	client_cert.pem	intermediate_CA.pem > chain.pem

       If you also want	to verify remote SMTP server  certificates  issued  by
       these  CAs,  you	can add	the CA certificates to the smtp_tls_CAfile, in
       which case it is	not necessary to have them in the  smtp_tls_cert_file,
       smtp_tls_dcert_file (obsolete) or smtp_tls_eccert_file.

       A certificate supplied here must	be usable as an	SSL client certificate
       and hence pass the "openssl verify -purpose sslclient ..." test.

       Example:

       smtp_tls_cert_file = $config_directory/chain.pem

       This feature is available in Postfix 2.2	and later.

smtp_tls_chain_files (default: empty)
       List of one or more PEM files, each holding one or  more	 private  keys
       directly	followed by a corresponding certificate	chain.	The file names
       are separated by	commas and/or whitespace.   This  parameter  obsoletes
       the  legacy algorithm-specific key and certificate file settings.  When
       this parameter is non-empty, the	legacy parameters are ignored,	and  a
       warning is logged if any	are also non-empty.

       With  the proliferation of multiple private key algorithms-which, as of
       OpenSSL 1.1.1, include DSA (obsolete), RSA, ECDSA, Ed25519 and Ed448-it
       is increasingly impractical to use separate parameters to configure the
       key and certificate chain for each algorithm.  Therefore,  Postfix  now
       supports	 storing multiple keys and corresponding certificate chains in
       a single	file or	in a set of files.

       Each key	must appear immediately	before the corresponding  certificate,
       optionally followed by additional issuer	certificates that complete the
       certificate chain for that key.	When  multiple	files  are  specified,
       they  are  equivalent  to a single file that is concatenated from those
       files in	the given order.  Thus,	while a	key must  always  precede  its
       certificate  and	issuer chain, it can be	in a separate file, so long as
       that file is listed immediately before the file that holds  the	corre-
       sponding	 certificate  chain.  Once all the files are concatenated, the
       sequence	of PEM objects must be:	key1, cert1,  [chain1],	 key2,	cert2,
       [chain2], ..., keyN, certN, [chainN].

       Storing	the private key	in the same file as the	corresponding certifi-
       cate is more reliable.  With the	key and	certificate in separate	files,
       there is	a chance that during key rollover a Postfix process might load
       a private key and certificate from separate  files  that	 don't	match.
       Various	operational errors may even result in a	persistent broken con-
       figuration in which the certificate does	not match the private key.

       The file	or files must contain at most one key of each type.   If,  for
       example,	 two or	more RSA keys and corresponding	chains are listed, de-
       pending on the version of OpenSSL either	only the last one will be used
       or  a  configuration  error may be detected.  Note that while "Ed25519"
       and "Ed448" are	considered  separate  algorithms,  the	various	 ECDSA
       curves  (typically  one of prime256v1, secp384r1	or secp521r1) are con-
       sidered as different parameters of a single "ECDSA" algorithm, so it is
       not presently possible to configure keys	for more than one ECDSA	curve.

       Example	(separate  files  for  each  key and corresponding certificate
       chain):

	   /usr/local/etc/postfix/main.cf:
	       smtp_tls_chain_files =
		   ${config_directory}/ed25519.pem,
		   ${config_directory}/ed448.pem,
		   ${config_directory}/rsa.pem

	   /usr/local/etc/postfix/ed25519.pem:
	       -----BEGIN PRIVATE KEY-----
	       MC4CAQAwBQYDK2VwBCIEIEJfbbO4BgBQGBg9NAbIJaDBqZb4bC4cOkjtAH+Efbz3
	       -----END	PRIVATE	KEY-----
	       -----BEGIN CERTIFICATE-----
	       MIIBKzCB3qADAgECAhQaw+rflRreYuUZBp0HuNn/e5rMZDAFBgMrZXAwFDESMBAG
	       ...
	       nC0egv51YPDWxEHom4QA
	       -----END	CERTIFICATE-----

	   /usr/local/etc/postfix/ed448.pem:
	       -----BEGIN PRIVATE KEY-----
	       MEcCAQAwBQYDK2VxBDsEOQf+m0P+G0qi+NZ0RolyeiE5zdlPQR8h8y4jByBifpIe
	       LNler7nzHQJ1SLcOiXFHXlxp/84VZuh32A==
	       -----END	PRIVATE	KEY-----
	       -----BEGIN CERTIFICATE-----
	       MIIBdjCB96ADAgECAhQSv4oP972KypOZPNPF4fmsiQoRHzAFBgMrZXEwFDESMBAG
	       ...
	       pQcWsx+4J29e6YWH3Cy/CdUaexKP4RPCZDrPX7bk5C2BQ+eeYOxyThMA
	       -----END	CERTIFICATE-----

	   /usr/local/etc/postfix/rsa.pem:
	       -----BEGIN PRIVATE KEY-----
	       MIIEvQIBADANBgkqhkiG9w0BAQEFAASCBKcwggSjAgEAAoIBAQDc4QusgkahH9rL
	       ...
	       ahQkZ3+krcaJvDSMgvu0tDc=
	       -----END	PRIVATE	KEY-----
	       -----BEGIN CERTIFICATE-----
	       MIIC+DCCAeCgAwIBAgIUIUkrbk1GAemPCT8i9wKsTGDH7HswDQYJKoZIhvcNAQEL
	       ...
	       Rirz15HGVNTK8wzFd+nulPzwUo6dH2IU8KazmyRi7OGvpyrMlm15TRE2oyE=
	       -----END	CERTIFICATE-----

       Example (all keys and certificates in a single file):

	   /usr/local/etc/postfix/main.cf:
	       smtp_tls_chain_files = ${config_directory}/chains.pem

	   /usr/local/etc/postfix/chains.pem:
	       -----BEGIN PRIVATE KEY-----
	       MC4CAQAwBQYDK2VwBCIEIEJfbbO4BgBQGBg9NAbIJaDBqZb4bC4cOkjtAH+Efbz3
	       -----END	PRIVATE	KEY-----
	       -----BEGIN CERTIFICATE-----
	       MIIBKzCB3qADAgECAhQaw+rflRreYuUZBp0HuNn/e5rMZDAFBgMrZXAwFDESMBAG
	       ...
	       nC0egv51YPDWxEHom4QA
	       -----END	CERTIFICATE-----
	       -----BEGIN PRIVATE KEY-----
	       MEcCAQAwBQYDK2VxBDsEOQf+m0P+G0qi+NZ0RolyeiE5zdlPQR8h8y4jByBifpIe
	       LNler7nzHQJ1SLcOiXFHXlxp/84VZuh32A==
	       -----END	PRIVATE	KEY-----
	       -----BEGIN CERTIFICATE-----
	       MIIBdjCB96ADAgECAhQSv4oP972KypOZPNPF4fmsiQoRHzAFBgMrZXEwFDESMBAG
	       ...
	       pQcWsx+4J29e6YWH3Cy/CdUaexKP4RPCZDrPX7bk5C2BQ+eeYOxyThMA
	       -----END	CERTIFICATE-----
	       -----BEGIN PRIVATE KEY-----
	       MIIEvQIBADANBgkqhkiG9w0BAQEFAASCBKcwggSjAgEAAoIBAQDc4QusgkahH9rL
	       ...
	       ahQkZ3+krcaJvDSMgvu0tDc=
	       -----END	PRIVATE	KEY-----
	       -----BEGIN CERTIFICATE-----
	       MIIC+DCCAeCgAwIBAgIUIUkrbk1GAemPCT8i9wKsTGDH7HswDQYJKoZIhvcNAQEL
	       ...
	       Rirz15HGVNTK8wzFd+nulPzwUo6dH2IU8KazmyRi7OGvpyrMlm15TRE2oyE=
	       -----END	CERTIFICATE-----

       This feature is available in Postfix 3.4	and later.

smtp_tls_cipherlist (default: empty)
       Obsolete	Postfix	< 2.3 control for the Postfix SMTP client  TLS	cipher
       list. As	this feature applies to	all TLS	security levels, it is easy to
       create interoperability problems	by choosing a non-default cipher list.
       Do not use a non-default	TLS cipher list	on hosts that deliver email to
       the public Internet: you	will be	unable to send email to	 servers  that
       only  support  the  ciphers you exclude.	Using a	restricted cipher list
       may be more appropriate for an internal MTA, where one can  exert  some
       control over the	TLS software and settings of the peer servers.

       Note: do	not use	"" quotes around the parameter value.

       This  feature  is available in Postfix version 2.2. It is not used with
       Postfix 2.3 and later; use smtp_tls_mandatory_ciphers instead.

smtp_tls_ciphers (default: medium)
       The minimum TLS cipher grade that the Postfix SMTP client will use with
       opportunistic  TLS  encryption.	Cipher	types  listed  in smtp_tls_ex-
       clude_ciphers are excluded from the base	definition of the selected ci-
       pher  grade.   The default value	is "medium" for	Postfix	releases after
       the middle of 2015, "export" for	older releases.

       When  TLS  is  mandatory	 the  cipher   grade   is   chosen   via   the
       smtp_tls_mandatory_ciphers  configuration parameter, see	there for syn-
       tax details. See	smtp_tls_policy_maps for information on	how to config-
       ure ciphers on a	per-destination	basis.

       This  feature is	available in Postfix 2.6 and later. With earlier Post-
       fix releases only the smtp_tls_mandatory_ciphers	 parameter  is	imple-
       mented, and opportunistic TLS always uses "export" or better (i.e. all)
       ciphers.

smtp_tls_connection_reuse (default: no)
       Try to make multiple deliveries	per  TLS-encrypted  connection.	  This
       uses  the  tlsproxy(8)  service to encrypt an SMTP connection, uses the
       scache(8) service to save that connection, and relies on	hints from the
       qmgr(8) daemon.

       See "Client-side	TLS connection reuse" for background details.

       This feature is available in Postfix 3.4	and later.

smtp_tls_dane_insecure_mx_policy (default: see postconf	-d output)
       The TLS policy for MX hosts with	"secure" TLSA records when the nexthop
       destination security level is dane, but the MX record was found via  an
       "insecure" MX lookup.  The choices are:

       may    The  TLSA	 records will be ignored and TLS will be optional.  If
	      the MX host does not appear to support STARTTLS, or the STARTTLS
	      handshake	fails, mail may	be sent	in the clear.

       encrypt
	      The  TLSA	 records  will signal a	requirement to use TLS.	 While
	      TLS encryption will be required, authentication will not be per-
	      formed.

       dane   The  TLSA	records	will be	used just as with "secure" MX records.
	      TLS encryption will be required, and, if at  least  one  of  the
	      TLSA records is "usable",	authentication will be required.  When
	      authentication succeeds, it will be logged  only	as  "Trusted",
	      not "Verified", because the MX host name could have been forged.
	      The   default   setting  for  Postfix  >=	 3.6  is  "dane"  with
	      "smtp_tls_security_level = dane",	otherwise "may". This behavior
	      was  backported  to  Postfix  versions  3.5.9,  3.4.19,  3.3.16.
	      3.2.21.  With earlier Postfix versions the default  setting  was
	      always "dane".

       Though  with  "insecure"	 MX  records an	active attacker	can compromise
       SMTP transport security by returning forged MX  records,	 such  attacks
       are  "tamper-evident" since any forged MX hostnames will	be recorded in
       the mail	logs.  Attackers who place a high value	on staying hidden  may
       be deterred from	forging	MX records.

       This  feature  is available in Postfix 3.1 and later. The may policy is
       backwards-compatible with earlier Postfix versions.

smtp_tls_dcert_file (default: empty)
       File with the Postfix SMTP client DSA certificate in PEM	format.	  This
       file may	also contain the Postfix SMTP client private DSA key.  The DSA
       algorithm is obsolete and should	not be used.

       See the discussion under	smtp_tls_cert_file for more details.

       Example:

       smtp_tls_dcert_file = $config_directory/client-dsa.pem

       This feature is available in Postfix 2.2	and later.

smtp_tls_dkey_file (default: $smtp_tls_dcert_file)
       File with the Postfix SMTP client DSA private key in PEM	format.	  This
       file  may be combined with the Postfix SMTP client DSA certificate file
       specified with $smtp_tls_dcert_file. The	DSA algorithm is obsolete  and
       should not be used.

       The  private key	must be	accessible without a pass-phrase, i.e. it must
       not be encrypted. File permissions should grant read-only access	to the
       system superuser	account	("root"), and no access	to anyone else.

       This feature is available in Postfix 2.2	and later.

smtp_tls_eccert_file (default: empty)
       File  with  the	Postfix	 SMTP  client ECDSA certificate	in PEM format.
       This file may also contain the Postfix SMTP client ECDSA	 private  key.
       With Postfix >= 3.4 the preferred way to	configure client keys and cer-
       tificates is via	the "smtp_tls_chain_files" parameter.

       See the discussion under	smtp_tls_cert_file for more details.

       Example:

       smtp_tls_eccert_file = $config_directory/ecdsa-ccert.pem

       This feature is available in Postfix 2.6	and  later,  when  Postfix  is
       compiled	and linked with	OpenSSL	1.0.0 or later.

smtp_tls_eckey_file (default: $smtp_tls_eccert_file)
       File  with  the	Postfix	 SMTP  client ECDSA private key	in PEM format.
       This file may be	combined with the Postfix SMTP client  ECDSA  certifi-
       cate  file  specified  with $smtp_tls_eccert_file.  With	Postfix	>= 3.4
       the preferred way to configure client keys and certificates is via  the
       "smtp_tls_chain_files" parameter.

       The  private key	must be	accessible without a pass-phrase, i.e. it must
       not be encrypted. File permissions should grant read-only access	to the
       system superuser	account	("root"), and no access	to anyone else.

       This  feature  is  available  in	Postfix	2.6 and	later, when Postfix is
       compiled	and linked with	OpenSSL	1.0.0 or later.

smtp_tls_enforce_peername (default: yes)
       With mandatory TLS encryption, require  that  the  remote  SMTP	server
       hostname	matches	the information	in the remote SMTP server certificate.
       As of RFC 2487 the requirements for hostname checking for  MTA  clients
       are not specified.

       This  option  can  be set to "no" to disable strict peer	name checking.
       This setting has	no effect on sessions  that  are  controlled  via  the
       smtp_tls_per_site table.

       Disabling the hostname verification can make sense in a closed environ-
       ment where special CAs are created.  If not used	carefully, this	option
       opens  the  danger  of  a "man-in-the-middle" attack (the CommonName of
       this attacker will be logged).

       This feature is available in Postfix 2.2	and later.  With  Postfix  2.3
       and later use smtp_tls_security_level instead.

smtp_tls_exclude_ciphers (default: empty)
       List of ciphers or cipher types to exclude from the Postfix SMTP	client
       cipher list at all TLS security levels. This  is	 not  an  OpenSSL  ci-
       pherlist,  it  is  a simple list	separated by whitespace	and/or commas.
       The elements are	a single cipher, or one	or more	"+"  separated	cipher
       properties,  in which case only ciphers matching	all the	properties are
       excluded.

       Examples	(some of these will cause problems):

	   smtp_tls_exclude_ciphers = aNULL
	   smtp_tls_exclude_ciphers = MD5, DES
	   smtp_tls_exclude_ciphers = DES+MD5
	   smtp_tls_exclude_ciphers = AES256-SHA, DES-CBC3-MD5
	   smtp_tls_exclude_ciphers = kEDH+aRSA

       The first setting disables anonymous ciphers. The next setting disables
       ciphers	that  use the MD5 digest algorithm or the (single) DES encryp-
       tion algorithm. The next	setting	disables ciphers that use MD5 and  DES
       together.   The	next setting disables the two ciphers "AES256-SHA" and
       "DES-CBC3-MD5". The last	setting	disables ciphers that  use  "EDH"  key
       exchange	with RSA authentication.

       This feature is available in Postfix 2.3	and later.

smtp_tls_fingerprint_cert_match	(default: empty)
       List  of	acceptable remote SMTP server certificate fingerprints for the
       "fingerprint" TLS security  level  (smtp_tls_security_level  =  finger-
       print). At this security	level, Certification Authorities are not used,
       and certificate expiration times	are ignored. Instead, server  certifi-
       cates are verified directly via their certificate fingerprint or	public
       key fingerprint (Postfix	2.9 and	later).	The fingerprint	is  a  message
       digest  of the server certificate (or public key). The digest algorithm
       is selected via the smtp_tls_fingerprint_digest parameter.

       The colons between each pair of nibbles in the  fingerprint  value  are
       optional	 (Postfix  >= 3.6). These were required	in earlier Postfix re-
       leases.

       When an smtp_tls_policy_maps table entry	 specifies  the	 "fingerprint"
       security	 level,	 any "match" attributes	in that	entry specify the list
       of valid	fingerprints for the corresponding destination.	Multiple  fin-
       gerprints can be	combined with a	"|" delimiter in a single match	attri-
       bute, or	multiple match attributes can be employed.

       Example:	Certificate fingerprint	verification  with  internal  mailhub.
       Two  matching  fingerprints  are	 listed. The relayhost may be multiple
       physical	hosts behind a load-balancer, each with	its own	private/public
       key  and	self-signed certificate. Alternatively,	a single relayhost may
       be in the process of switching from one set of private/public  keys  to
       another,	and both keys are trusted just prior to	the transition.

	   relayhost = [mailhub.example.com]
	   smtp_tls_security_level = fingerprint
	   smtp_tls_fingerprint_digest = sha256
	   smtp_tls_fingerprint_cert_match =
	       cd:fc:d8:db:f8:c4:82:96:6c:...:28:71:e8:f5:8d:a5:0d:9b:d4:a6
	       dd:5c:ef:f5:c3:bc:64:25:36:...:99:36:06:ce:40:ef:de:2e:ad:a4

       Example:	 Certificate  fingerprint  verification	with selected destina-
       tions.  As in the example above,	we show	two matching fingerprints:

	   /usr/local/etc/postfix/main.cf:
	       smtp_tls_policy_maps = hash:$config_directory/tls_policy
	       smtp_tls_fingerprint_digest = sha256

	   /usr/local/etc/postfix/tls_policy:
	       example.com fingerprint
		   match=51:e9:af:2e:1e:40:1f:...:64:0a:30:35:2d:09:16:31:5a:eb:82:76
		   match=b6:b4:72:34:e2:59:cd:...:c2:ca:63:0d:4d:cc:2c:7d:84:de:e6:2f

       This feature is available in Postfix 2.5	and later.

smtp_tls_fingerprint_digest (default: see postconf -d output)
       The message digest algorithm used to construct remote SMTP server  cer-
       tificate	  fingerprints.	  At  the  "fingerprint"  TLS  security	 level
       (smtp_tls_security_level	= fingerprint),	the server certificate is ver-
       ified  by  directly  matching its certificate fingerprint or its	public
       key fingerprint (Postfix	2.9 and	later).	The fingerprint	is the message
       digest of the server certificate	(or its	public key) using the selected
       algorithm. With a digest	algorithm resistant to "second pre-image"  at-
       tacks,  it  is  not  feasible to	create a new public key	and a matching
       certificate (or public/private key-pair)	that has the same fingerprint.

       The default algorithm is	sha256 with Postfix >= 3.6 and the compatibil-
       ity_level  set to 3.6 or	higher.	With Postfix <=	3.5, the default algo-
       rithm is	md5.

       The best-practice algorithm is now  sha256.  Recent  advances  in  hash
       function	cryptanalysis have led to md5 and sha1 being deprecated	in fa-
       vor of sha256.  However,	as long	as there are no	known "second  pre-im-
       age"  attacks  against the older	algorithms, their use in this context,
       though not recommended, is still	likely safe.

       While additional	digest algorithms are often available  with  OpenSSL's
       libcrypto, only those used by libssl in SSL cipher suites are available
       to Postfix.  You'll likely find	support	 for  md5,  sha1,  sha256  and
       sha512.

       To find the fingerprint of a specific certificate file, with a specific
       digest algorithm, run:

	   $ openssl x509 -noout -fingerprint -digest -in certfile.pem

       The text	to the right of	the "="	sign is	the desired fingerprint.   For
       example:

	   $ openssl x509 -noout -fingerprint -sha256 -in cert.pem
	   SHA256 Fingerprint=D4:6A:AB:19:24:...:BB:A6:CB:66:82:C0:8E:9B:EE:29:A8:1A

       To  extract  the	 public	key fingerprint	from an	X.509 certificate, you
       need to extract the public key from the certificate and compute the ap-
       propriate  digest  of its DER (ASN.1) encoding. With OpenSSL the	"-pub-
       key" option of the "x509" command extracts the  public  key  always  in
       "PEM"  format.  We pipe the result to another OpenSSL command that con-
       verts the key to	DER and	then to	the "dgst" command to compute the fin-
       gerprint.

       The  actual  command  to	transform the key to DER format	depends	on the
       version of OpenSSL used.	As of OpenSSL 1.0.0, the "pkey"	 command  sup-
       ports all key types.

	   # OpenSSL >=	1.0 with SHA-256 fingerprints.
	   $ openssl x509 -in cert.pem -noout -pubkey |
	       openssl pkey -pubin -outform DER	|
	       openssl dgst -sha256 -c
	   (stdin)= 64:3f:1f:f6:e5:1e:d4:2a:56:...:fc:09:1a:61:98:b5:bc:7c:60:58

       The Postfix SMTP	server and client log the peer (leaf) certificate fin-
       gerprint	and the	public key fingerprint when the	TLS loglevel is	 2  or
       higher.

       This feature is available in Postfix 2.5	and later.

smtp_tls_force_insecure_host_tlsa_lookup (default: no)
       Lookup  the  associated	DANE TLSA RRset	even when a hostname is	not an
       alias and its address records lie in an unsigned	 zone.	 This  is  un-
       likely to ever yield DNSSEC validated results, since child zones	of un-
       signed zones are	also unsigned in the absence of	DLV or locally config-
       ured  non-root  trust-anchors.  We anticipate that such mechanisms will
       not be used for just the	"_tcp" subdomain of a host.   Suppressing  the
       TLSA RRset lookup reduces latency and avoids potential interoperability
       problems	with nameservers for unsigned zones that are not  prepared  to
       handle the new TLSA RRset.

       This feature is available in Postfix 2.11.

smtp_tls_key_file (default: $smtp_tls_cert_file)
       File  with the Postfix SMTP client RSA private key in PEM format.  This
       file may	be combined with the Postfix SMTP client RSA certificate  file
       specified  with $smtp_tls_cert_file.  With Postfix >= 3.4 the preferred
       way  to	configure  client   keys   and	 certificates	is   via   the
       "smtp_tls_chain_files" parameter.

       The  private key	must be	accessible without a pass-phrase, i.e. it must
       not be encrypted. File permissions should grant read-only access	to the
       system superuser	account	("root"), and no access	to anyone else.

       Example:

       smtp_tls_key_file = $smtp_tls_cert_file

       This feature is available in Postfix 2.2	and later.

smtp_tls_loglevel (default: 0)
       Enable  additional  Postfix  SMTP client	logging	of TLS activity.  Each
       logging level also includes the information that	is logged at  a	 lower
       logging level.

	      0	Disable	logging	of TLS activity.

	      1	 Log  only  a summary message on TLS handshake completion - no
	      logging of remote	SMTP server certificate	trust-chain  verifica-
	      tion  errors if server certificate verification is not required.
	      With Postfix 2.8 and earlier, log	the summary message and	uncon-
	      ditionally log trust-chain verification errors.

	      2	Also log levels	during TLS negotiation.

	      3	Also log the hexadecimal and ASCII dump	of the TLS negotiation
	      process.

	      4	Also log the hexadecimal and ASCII dump	of complete  transmis-
	      sion after STARTTLS.

       Do  not	use  "smtp_tls_loglevel	= 2" or	higher except in case of prob-
       lems. Use of loglevel 4 is strongly discouraged.

       This feature is available in Postfix 2.2	and later.

smtp_tls_mandatory_ciphers (default: medium)
       The minimum TLS cipher grade that the Postfix SMTP client will use with
       mandatory  TLS  encryption.  The	default	value "medium" is suitable for
       most destinations with which you	may want to enforce TLS, and is	beyond
       the  reach  of  today's cryptanalytic methods. See smtp_tls_policy_maps
       for information on how to configure ciphers on a	per-destination	basis.

       The following cipher grades are supported:

       export Enable "EXPORT" grade or better OpenSSL ciphers.	The underlying
	      cipherlist is specified via the tls_export_cipherlist configura-
	      tion parameter, which you	are strongly encouraged	not to change.
	      This choice is insecure and SHOULD NOT be	used.

       low    Enable  "LOW"  grade  or better OpenSSL ciphers.	The underlying
	      cipherlist is specified via the tls_low_cipherlist configuration
	      parameter,  which	 you  are  strongly  encouraged	not to change.
	      This choice is insecure and SHOULD NOT be	used.

       medium Enable "MEDIUM" grade or better OpenSSL ciphers.	The underlying
	      cipherlist is specified via the tls_medium_cipherlist configura-
	      tion parameter, which you	are strongly encouraged	not to change.

       high   Enable only "HIGH" grade OpenSSL ciphers.	 This setting  may  be
	      appropriate  when	 all mandatory TLS destinations	(e.g. when all
	      mail is routed to	a suitably capable relayhost) support at least
	      one  "HIGH" grade	cipher.	The underlying cipherlist is specified
	      via the tls_high_cipherlist configuration	parameter,  which  you
	      are strongly encouraged not to change.

       null   Enable  only the "NULL" OpenSSL ciphers, these provide authenti-
	      cation without encryption.  This setting is only appropriate  in
	      the  rare	case that all servers are prepared to use NULL ciphers
	      (not normally enabled in TLS servers). A plausible  use-case  is
	      an LMTP server listening on a UNIX-domain	socket that is config-
	      ured to support "NULL" ciphers.  The  underlying	cipherlist  is
	      specified	 via  the tls_null_cipherlist configuration parameter,
	      which you	are strongly encouraged	not to change.

       The underlying cipherlists for grades other than	"null" include	anony-
       mous  ciphers,  but these are automatically filtered out	if the Postfix
       SMTP client is configured to verify server certificates.	 You are  very
       unlikely	 to  need to take any steps to exclude anonymous ciphers, they
       are excluded automatically as necessary.	 If you	must exclude anonymous
       ciphers	at  the	 "may"	or "encrypt" security levels, when the Postfix
       SMTP client does	not need or use	peer certificates,  set	 "smtp_tls_ex-
       clude_ciphers  =	 aNULL". To exclude anonymous ciphers only when	TLS is
       enforced, set "smtp_tls_mandatory_exclude_ciphers = aNULL".

       This feature is available in Postfix 2.3	and later.

smtp_tls_mandatory_exclude_ciphers (default: empty)
       Additional list of ciphers or cipher types to exclude from the  Postfix
       SMTP  client  cipher  list  at mandatory	TLS security levels. This list
       works in	addition to the	exclusions  listed  with  smtp_tls_exclude_ci-
       phers (see there	for syntax details).

       Starting	with Postfix 2.6, the mandatory	cipher exclusions can be spec-
       ified on	a per-destination basis	via the	TLS  policy  "exclude"	attri-
       bute. See smtp_tls_policy_maps for notes	and examples.

       This feature is available in Postfix 2.3	and later.

smtp_tls_mandatory_protocols (default: see postconf -d output)
       TLS  protocols that the Postfix SMTP client will	use with mandatory TLS
       encryption.  In main.cf the values are separated	by whitespace,	commas
       or colons. In the policy	table "protocols" attribute (see smtp_tls_pol-
       icy_maps) the only valid	separator is colon. An empty value means allow
       all protocols.

       The valid protocol names	(see SSL_get_version(3)) are "SSLv2", "SSLv3",
       "TLSv1",	"TLSv1.1", "TLSv1.2" and  "TLSv1.3".   Starting	 with  Postfix
       3.6,  the  default value	is ">=TLSv1", which sets TLS 1.0 as the	lowest
       supported TLS protocol version (see below).  Older releases use the "!"
       exclusion syntax, also described	below.

       As  of  Postfix 3.6, the	preferred way to limit the range of acceptable
       protocols is to set a lowest acceptable TLS protocol version  and/or  a
       highest	acceptable  TLS	 protocol version.  To set the lower bound in-
       clude an	element	of the form: ">=version" where version is a either one
       of  the TLS protocol names listed above,	or a hexadecimal number	corre-
       sponding	to the desired TLS protocol version (0301 for  TLS  1.0,  0302
       for  TLS	1.1, etc.).  For the upper bound, use "<=version".  There must
       be no whitespace	between	the ">=" or "<=" symbols and the protocol name
       or number.

       Hexadecimal  protocol  numbers  make  it	 possible  to specify protocol
       bounds for TLS versions that are	known to OpenSSL,  but	might  not  be
       known  to  Postfix.  They cannot	be used	with the legacy	exclusion syn-
       tax.  Leading "0" or "0x" prefixes are  supported,  but	not  required.
       Therefore,  "301",  "0301",  "0x301" and	"0x0301" are all equivalent to
       "TLSv1".	 Hexadecimal versions unknown to OpenSSL will fail to set  the
       upper  or  lower	bound, and a warning will be logged.  Hexadecimal ver-
       sions should only be used when Postfix is linked	with some future  ver-
       sion  of	 OpenSSL  that supports	TLS 1.4	or later, but Postfix does not
       yet support a symbolic name for that protocol version.

       Hexadecimal example (Postfix >= 3.6):

	   # Allow only	TLS 1.2	through	(hypothetical) TLS 1.4,	once supported
	   # in	some future version of OpenSSL (presently a warning is logged).
	   smtp_tls_mandatory_protocols	= >=TLSv1.2, <=0305
	   # Allow only	TLS 1.2	and up:
	   smtp_tls_mandatory_protocols	= >=0x0303

       With Postfix < 3.6 there	is no support for a minimum  or	 maximum  ver-
       sion, and the protocol range is configured via protocol exclusions.  To
       require at least	TLS 1.0, set "smtp_tls_mandatory_protocols  =  !SSLv2,
       !SSLv3".	Listing	the protocols to include, rather than the protocols to
       exclude,	is supported, but not recommended.  The	exclusion syntax  more
       accurately matches the underlying OpenSSL interface.

       When  using the exclusion syntax, take care to ensure that the range of
       protocols supported by the Postfix SMTP client is contiguous.   When  a
       protocol	 version  is  enabled, disabling any higher version implicitly
       disables	all versions above that	higher version.	 Thus, for example:

	   smtp_tls_mandatory_protocols	= !SSLv2, !SSLv3, !TLSv1.1

       also disables any protocol versions higher than	TLSv1.1	 leaving  only
       "TLSv1" enabled.

       Support	for "TLSv1.3" was introduced in	OpenSSL	1.1.1.	Disabling this
       protocol	via "!TLSv1.3" is supported since Postfix 3.4  (or  patch  re-
       leases >= 3.0.14, 3.1.10, 3.2.7 and 3.3.2).

       While the vast majority of SMTP servers with DANE TLSA records now sup-
       port at least TLS 1.2, a	few still only support TLS 1.0.	  If  you  use
       "dane"  or  "dane-only" it is best not to disable TLSv1,	except perhaps
       via the policy table for	destinations which you are sure	 will  support
       "TLSv1.2".

       See   the  documentation	 of  the  smtp_tls_policy_maps	parameter  and
       TLS_README for more information about security levels.

       Example:
       # Preferred syntax with Postfix >= 3.6:
       smtp_tls_mandatory_protocols = >=TLSv1.2, <=TLSv1.3
       # Legacy	syntax:
       smtp_tls_mandatory_protocols = !SSLv2, !SSLv3, !TLSv1, !TLSv1.1

       This feature is available in Postfix 2.3	and later.

smtp_tls_note_starttls_offer (default: no)
       Log the hostname	of a remote SMTP server	that offers STARTTLS, when TLS
       is not already enabled for that server.

       The logfile record looks	like:

       postfix/smtp[pid]:  Host	offered	STARTTLS: [name.of.host]

       This feature is available in Postfix 2.2	and later.

smtp_tls_per_site (default: empty)
       Optional	lookup tables with the Postfix SMTP client TLS usage policy by
       next-hop	destination and	by remote SMTP	server	hostname.   When  both
       lookups	succeed,  the more specific per-site policy (NONE, MUST, etc.)
       overrides the less specific one (MAY), and  the	more  secure  per-site
       policy (MUST, etc.) overrides the less secure one (NONE).  With Postfix
       2.3  and	 later	smtp_tls_per_site   is	 strongly   discouraged:   use
       smtp_tls_policy_maps instead.

       Use  of	the bare hostname as the per-site table	lookup key is discour-
       aged. Always use	the full destination nexthop (enclosed in  []  with  a
       possible	 ":port"  suffix).  A recipient	domain or MX-enabled transport
       next-hop	with no	port suffix may	look like  a  bare  hostname,  but  is
       still a suitable	destination.

       Specify	a  next-hop  destination  or  server hostname on the left-hand
       side; no	wildcards are allowed. The next-hop destination	is either  the
       recipient  domain, or the destination specified with a transport(5) ta-
       ble, the	relayhost parameter, or	the relay_transport parameter.	On the
       right hand side specify one of the following keywords:

       NONE   Don't  use TLS at	all. This overrides a less specific MAY	lookup
	      result from the alternate	host or	next-hop lookup	key, and over-
	      rides    the    global   smtp_use_tls,   smtp_enforce_tls,   and
	      smtp_tls_enforce_peername	settings.

       MAY    Try to use TLS if	the server announces support, otherwise	use an
	      unencrypted  connection.	This  has  less	precedence than	a more
	      specific result (including NONE)	from  the  alternate  host  or
	      next-hop	lookup key, and	has less precedence than the more spe-
	      cific global "smtp_enforce_tls = yes" or "smtp_tls_enforce_peer-
	      name = yes".

       MUST_NOPEERMATCH
	      Require  TLS encryption, but do not require that the remote SMTP
	      server hostname matches  the  information	 in  the  remote  SMTP
	      server certificate, or that the server certificate was issued by
	      a	trusted	CA. This overrides a less secure NONE or a  less  spe-
	      cific  MAY  lookup  result  from	the alternate host or next-hop
	      lookup key, and  overrides  the  global  smtp_use_tls,  smtp_en-
	      force_tls	and smtp_tls_enforce_peername settings.

       MUST   Require  TLS  encryption,	 require  that	the remote SMTP	server
	      hostname matches the information in the remote SMTP server  cer-
	      tificate,	 and  require  that the	remote SMTP server certificate
	      was issued by a trusted CA. This overrides a less	secure NONE or
	      MUST_NOPEERMATCH	or  a less specific MAY	lookup result from the
	      alternate	host or	next-hop lookup	key, and overrides the	global
	      smtp_use_tls,   smtp_enforce_tls	and  smtp_tls_enforce_peername
	      settings.

       The above keywords correspond to	the "none", "may", "encrypt" and "ver-
       ify"  security levels for the new smtp_tls_security_level parameter in-
       troduced	in Postfix 2.3.	Starting with Postfix 2.3,  and	 independently
       of  how	the  policy  is	 specified, the	smtp_tls_mandatory_ciphers and
       smtp_tls_mandatory_protocols parameters apply when  TLS	encryption  is
       mandatory.  Connections	for which encryption is	optional typically en-
       able all	"export" grade and better ciphers  (see	 smtp_tls_ciphers  and
       smtp_tls_protocols).

       As long as no secure DNS	lookup mechanism is available, false hostnames
       in MX or	CNAME responses	can change the server  hostname	 that  Postfix
       uses  for  TLS  policy lookup and server	certificate verification. Even
       with a perfect match between the	server hostname	and  the  server  cer-
       tificate,  there	is no guarantee	that Postfix is	connected to the right
       server.	See TLS_README (Closing	a DNS loophole with obsolete  per-site
       TLS policies) for a possible work-around.

       This  feature  is  available in Postfix 2.2 and later. With Postfix 2.3
       and later use smtp_tls_policy_maps instead.

smtp_tls_policy_maps (default: empty)
       Optional	lookup tables with the Postfix SMTP client TLS security	policy
       by  next-hop  destination;  when	 a  non-empty value is specified, this
       overrides the obsolete smtp_tls_per_site	parameter.  See	TLS_README for
       a more detailed discussion of TLS security levels.

       Specify zero or more "type:name"	lookup tables, separated by whitespace
       or comma. Tables	will be	searched in the	specified order	until a	 match
       is found.

       The TLS policy table is indexed by the full next-hop destination, which
       is either the recipient domain, or the verbatim next-hop	 specified  in
       the   transport	 table,	  $local_transport,  $virtual_transport,  $re-
       lay_transport or	$default_transport. This includes any enclosing	square
       brackets	 and  any non-default destination server port suffix. The LMTP
       socket type prefix (inet: or unix:) is not included in the lookup key.

       Only the	next-hop domain, or $myhostname	 with  LMTP  over  UNIX-domain
       sockets,	 is used as the	nexthop	name for certificate verification. The
       port and	any enclosing square brackets are used	in  the	 table	lookup
       key, but	are not	used for server	name verification.

       When  the lookup	key is a domain	name without enclosing square brackets
       or any :port suffix (typically the recipient domain), and the full  do-
       main  is	 not  found in the table, just as with the transport(5)	table,
       the parent domain starting with a leading "." is	 matched  recursively.
       This allows one to specify a security policy for	a recipient domain and
       all its sub-domains.

       The lookup result is a security level, followed by an optional list  of
       whitespace  and/or  comma separated name=value attributes that override
       related main.cf settings. The TLS security levels in order of  increas-
       ing security are:

       none   No TLS. No additional attributes are supported at	this level.

       may    Opportunistic TLS. Since sending in the clear is acceptable, de-
	      manding stronger than default TLS	security merely	reduces	inter-
	      operability.  The	optional "ciphers", "exclude", and "protocols"
	      attributes (available for	opportunistic TLS with Postfix >= 2.6)
	      and  "connection_reuse"  attribute (Postfix >= 3.4) override the
	      "smtp_tls_ciphers", "smtp_tls_exclude_ciphers", "smtp_tls_proto-
	      cols", and "smtp_tls_connection_reuse" configuration parameters.
	      In the policy table, multiple ciphers, protocols or excluded ci-
	      phers  must  be separated	by colons, as attribute	values may not
	      contain whitespace or commas. When opportunistic TLS  handshakes
	      fail,  Postfix  retries  the connection with TLS disabled.  This
	      allows mail delivery to sites with non-interoperable TLS	imple-
	      mentations.

       encrypt
	      Mandatory	TLS encryption.	At this	level and higher, the optional
	      "protocols"  attribute  overrides	 the  main.cf  smtp_tls_manda-
	      tory_protocols parameter,	the optional "ciphers" attribute over-
	      rides the	main.cf	smtp_tls_mandatory_ciphers parameter, the  op-
	      tional  "exclude"	 attribute  (Postfix  >=  2.6)	overrides  the
	      main.cf smtp_tls_mandatory_exclude_ciphers  parameter,  and  the
	      optional "connection_reuse" attribute (Postfix >=	3.4) overrides
	      the main.cf smtp_tls_connection_reuse parameter. In  the	policy
	      table,  multiple	ciphers, protocols or excluded ciphers must be
	      separated	by colons, as attribute	values may not contain	white-
	      space or commas.

       dane   Opportunistic  DANE  TLS.	 The TLS policy	for the	destination is
	      obtained via TLSA	records	in DNSSEC.  If	no  TLSA  records  are
	      found,  the  effective  security	level  used  is	 may.  If TLSA
	      records are found, but none are usable, the  effective  security
	      level is encrypt.	 When usable TLSA records are obtained for the
	      remote SMTP server, the server certificate must match  the  TLSA
	      records.	 RFC 7672 (DANE) TLS authentication and	DNSSEC support
	      is available with	Postfix	2.11 and later.	The optional  "connec-
	      tion_reuse"  attribute  (Postfix	>=  3.4) overrides the main.cf
	      smtp_tls_connection_reuse	parameter.  When the  effective	 secu-
	      rity  level  used	is may,	the optional "ciphers",	"exclude", and
	      "protocols"   attributes	 (Postfix   >=	 2.6)	override   the
	      "smtp_tls_ciphers",	 "smtp_tls_exclude_ciphers",	   and
	      "smtp_tls_protocols" configuration parameters.  When the	effec-
	      tive  security  level  used  is encrypt, the optional "ciphers",
	      "exclude", and "protocols" attributes (Postfix >=	2.6)  override
	      the     "smtp_tls_mandatory_ciphers",    "smtp_tls_mandatory_ex-
	      clude_ciphers", and "smtp_tls_mandatory_protocols" configuration
	      parameters.

       dane-only
	      Mandatory	 DANE  TLS.  The TLS policy for	the destination	is ob-
	      tained via TLSA records in  DNSSEC.   If	no  TLSA  records  are
	      found,  or none are usable, no connection	is made	to the server.
	      When usable TLSA	records	 are  obtained	for  the  remote  SMTP
	      server, the server certificate must match	the TLSA records.  RFC
	      7672 (DANE) TLS authentication and DNSSEC	support	 is  available
	      with  Postfix 2.11 and later. The	optional "ciphers", "exclude",
	      and  "protocols"	attributes  (Postfix  >=  2.6)	override   the
	      "smtp_tls_mandatory_ciphers",    "smtp_tls_mandatory_exclude_ci-
	      phers", and "smtp_tls_mandatory_protocols" configuration parame-
	      ters. The	optional "connection_reuse" attribute (Postfix >= 3.4)
	      overrides	the main.cf smtp_tls_connection_reuse parameter.

       fingerprint
	      Certificate fingerprint verification. Available with Postfix 2.5
	      and later. At this security level, there are no trusted Certifi-
	      cation Authorities.  The	certificate  trust  chain,  expiration
	      date,  ... are not checked. Instead, the optional	"match"	attri-
	      bute, or else the	main.cf	smtp_tls_fingerprint_cert_match	param-
	      eter,  lists the certificate fingerprints	or the public key fin-
	      gerprint (Postfix	2.9 and	later) of the  valid  server  certifi-
	      cate.  The digest	algorithm used to calculate the	fingerprint is
	      selected by the smtp_tls_fingerprint_digest parameter.  Multiple
	      fingerprints  can	 be  combined with a "|" delimiter in a	single
	      match attribute, or multiple match attributes can	 be  employed.
	      The  ":"	character  is not used as a delimiter as it occurs be-
	      tween each pair of fingerprint  (hexadecimal)  digits.  The  op-
	      tional "ciphers",	"exclude", and "protocols" attributes (Postfix
	      >=    2.6)    override	 the	 "smtp_tls_mandatory_ciphers",
	      "smtp_tls_mandatory_exclude_ciphers",    and    "smtp_tls_manda-
	      tory_protocols" configuration parameters.	The optional  "connec-
	      tion_reuse"  attribute  (Postfix	>=  3.4) overrides the main.cf
	      smtp_tls_connection_reuse	parameter.

       verify Mandatory	TLS verification.  At  this  security  level,  DNS  MX
	      lookups  are  trusted to be secure enough, and the name verified
	      in the server certificate	is  usually  obtained  indirectly  via
	      unauthenticated  DNS MX lookups.	The optional "match" attribute
	      overrides	the main.cf smtp_tls_verify_cert_match	parameter.  In
	      the policy table,	multiple match patterns	and strategies must be
	      separated	by colons.  In practice	explicit control over matching
	      is  more	common	with the "secure" policy, described below. The
	      optional "ciphers", "exclude", and "protocols" attributes	(Post-
	      fix   >=	 2.6)	override   the	 "smtp_tls_mandatory_ciphers",
	      "smtp_tls_mandatory_exclude_ciphers",    and    "smtp_tls_manda-
	      tory_protocols"  configuration parameters. The optional "connec-
	      tion_reuse" attribute (Postfix >=	 3.4)  overrides  the  main.cf
	      smtp_tls_connection_reuse	parameter.

       secure Secure-channel  TLS.  At	this  security	level, DNS MX lookups,
	      though potentially used  to  determine  the  candidate  next-hop
	      gateway  IP  addresses,  are not trusted to be secure enough for
	      TLS peername verification. Instead, the default name verified in
	      the  server  certificate is obtained directly from the next-hop,
	      or is explicitly specified via the  optional  "match"  attribute
	      which  overrides	the main.cf smtp_tls_secure_cert_match parame-
	      ter. In the policy table,	multiple match patterns	and strategies
	      must be separated	by colons.  The	match attribute	is most	useful
	      when multiple domains are	supported by a common server: the pol-
	      icy  entries  for	 additional domains specify matching rules for
	      the primary domain certificate. While transport table  overrides
	      that route the secondary domains to the primary nexthop also al-
	      low secure verification, they risk delivery to the wrong	desti-
	      nation when domains change hands or are re-assigned to new gate-
	      ways. With the "match" attribute approach, routing is  not  per-
	      turbed,  and  mail  is deferred if verification of a new MX host
	      fails. The optional "ciphers", "exclude",	 and  "protocols"  at-
	      tributes	(Postfix  >= 2.6) override the "smtp_tls_mandatory_ci-
	      phers",	     "smtp_tls_mandatory_exclude_ciphers",	   and
	      "smtp_tls_mandatory_protocols" configuration parameters. The op-
	      tional "connection_reuse"	attribute (Postfix >=  3.4)  overrides
	      the main.cf smtp_tls_connection_reuse parameter.

       Example:

       /usr/local/etc/postfix/main.cf:
	   smtp_tls_policy_maps	= hash:$config_directory/tls_policy
	   # Postfix 2.5 and later.
	   #
	   # The default digest	is sha256 with Postfix >= 3.6 and
	   # compatibility level >= 3.
	   #
	   smtp_tls_fingerprint_digest = sha256

       /usr/local/etc/postfix/tls_policy:
	   example.edu		       none
	   example.mil		       may
	   example.gov		       encrypt protocols=TLSv1
	   example.com		       verify ciphers=high
	   example.net		       secure
	   .example.net		       secure match=.example.net:example.net
	   [mail.example.org]:587      secure match=nexthop
	   # Postfix 2.5 and later
	   [thumb.example.org]		fingerprint
	       match=b6:b4:72:34:e2:59:cd:...:c2:ca:63:0d:4d:cc:2c:7d:84:de:e6:2f
	       match=51:e9:af:2e:1e:40:1f:...:64:0a:30:35:2d:09:16:31:5a:eb:82:76

       Note:  The  "hostname"  strategy	 if listed in a	non-default setting of
       smtp_tls_secure_cert_match or in	the "match" attribute  in  the	policy
       table  can  render the "secure" level vulnerable	to DNS forgery.	Do not
       use the "hostname" strategy for secure-channel configurations in	 envi-
       ronments	where DNS security is not assured.

       This feature is available in Postfix 2.3	and later.

smtp_tls_protocols (default: see postconf -d output)
       TLS  protocols that the Postfix SMTP client will	use with opportunistic
       TLS encryption.	In main.cf the values  are  separated  by  whitespace,
       commas  or  colons.  In	the  policy  table  "protocols"	attribute (see
       smtp_tls_policy_maps) the only valid  separator	is  colon.   An	 empty
       value means allow all protocols.

       The valid protocol names	(see SSL_get_version(3)) are "SSLv2", "SSLv3",
       "TLSv1",	"TLSv1.1", "TLSv1.2" and  "TLSv1.3".   Starting	 with  Postfix
       3.6,  the  default value	is ">=TLSv1", which sets TLS 1.0 as the	lowest
       supported TLS protocol version (see below).  Older releases use the "!"
       exclusion syntax, also described	below.

       As  of  Postfix 3.6, the	preferred way to limit the range of acceptable
       protocols is to set the lowest acceptable TLS protocol  version	and/or
       the  highest  acceptable	 TLS protocol version.	To set the lower bound
       include an element of the form: ">=version" where version is either one
       of  the TLS protocol names listed above,	or a hexadecimal number	corre-
       sponding	to the desired TLS protocol version (0301 for  TLS  1.0,  0302
       for  TLS	1.1, etc.).  For the upper bound, use "<=version".  There must
       be no whitespace	between	the ">=" or "<=" symbols and the protocol name
       or number.

       Hexadecimal  protocol  numbers  make  it	 possible  to specify protocol
       bounds for TLS versions that are	known to OpenSSL,  but	might  not  be
       known  to  Postfix.  They cannot	be used	with the legacy	exclusion syn-
       tax.  Leading "0" or "0x" prefixes are  supported,  but	not  required.
       Therefore,  "301",  "0301",  "0x301" and	"0x0301" are all equivalent to
       "TLSv1".	 Hexadecimal versions unknown to OpenSSL will fail to set  the
       upper  or  lower	bound, and a warning will be logged.  Hexadecimal ver-
       sions should only be used when Postfix is linked	with some future  ver-
       sion  of	 OpenSSL  that supports	TLS 1.4	or later, but Postfix does not
       yet support a symbolic name for that protocol version.

       Hexadecimal example (Postfix >= 3.6):

	   # Allow only	TLS 1.0	through	(hypothetical) TLS 1.4,	once supported
	   # in	some future version of OpenSSL (presently a warning is logged).
	   smtp_tls_protocols =	>=TLSv1, <=0305
	   # Allow only	TLS 1.0	and up:
	   smtp_tls_protocols =	>=0x0301

       With Postfix < 3.6 there	is no support for a minimum  or	 maximum  ver-
       sion, and the protocol range is configured via protocol exclusions.  To
       require at least	TLS 1.0, set "smtp_tls_protocols  =  !SSLv2,  !SSLv3".
       Listing	the protocols to include, rather than protocols	to exclude, is
       supported, but not recommended.	The  exclusion	form  more  accurately
       matches the underlying OpenSSL interface.

       When  using the exclusion syntax, take care to ensure that the range of
       protocols advertised by an SSL/TLS client is contiguous.	 When a	proto-
       col  version  is	 enabled, disabling any	higher version implicitly dis-
       ables all versions above	that higher version.  Thus, for	example:

	   smtp_tls_protocols =	!SSLv2,	!SSLv3,	!TLSv1.1
       also disables any protocols version higher than	TLSv1.1	 leaving  only
       "TLSv1" enabled.

       Support	for "TLSv1.3" was introduced in	OpenSSL	1.1.1.	Disabling this
       protocol	via "!TLSv1.3" is supported since Postfix 3.4  (or  patch  re-
       leases >= 3.0.14, 3.1.10, 3.2.7 and 3.3.2).

       Example:
       # Preferred syntax with Postfix >= 3.6:
       smtp_tls_protocols = >=TLSv1, <=TLSv1.3
       # Legacy	syntax:
       smtp_tls_protocols = !SSLv2, !SSLv3

       This feature is available in Postfix 2.6	and later.

smtp_tls_scert_verifydepth (default: 9)
       The  verification depth for remote SMTP server certificates. A depth of
       1 is sufficient if the issuing CA is listed in a	local CA file.

       The default verification	depth is 9 (the	OpenSSL	default) for  compati-
       bility with earlier Postfix behavior. Prior to Postfix 2.5, the default
       value was 5, but	the limit was not actually enforced. If	you  have  set
       this  to	 a  lower  non-default	value,	certificates with longer trust
       chains may now fail to verify. Certificate chains with 1	or 2  CAs  are
       common,	deeper	chains	are  more  rare	and any	number between 5 and 9
       should suffice in practice. You can choose a lower number if, for exam-
       ple,  you  trust	 certificates directly signed by an issuing CA but not
       any CAs it delegates to.

       This feature is available in Postfix 2.2	and later.

smtp_tls_secure_cert_match (default: nexthop, dot-nexthop)
       How the Postfix SMTP client verifies the	 server	 certificate  peername
       for  the	 "secure"  TLS	security level.	In a "secure" TLS policy table
       ($smtp_tls_policy_maps) entry the optional "match" attribute  overrides
       this main.cf setting.

       This  parameter	specifies one or more patterns or strategies separated
       by commas, whitespace or	colons.	 In the	policy table  the  only	 valid
       separator is the	colon character.

       For   a	description  of	 the  pattern  and  strategy  syntax  see  the
       smtp_tls_verify_cert_match parameter. The "hostname" strategy should be
       avoided	in this	context, as in the absence of a	secure global DNS, us-
       ing the results of MX lookups in	certificate verification is not	immune
       to active (man-in-the-middle) attacks on	DNS.

       Sample main.cf setting:

	   smtp_tls_secure_cert_match =	nexthop

       Sample policy table override:

	   example.net	   secure match=example.com:.example.com
	   .example.net	   secure match=example.com:.example.com

       This feature is available in Postfix 2.3	and later.

smtp_tls_security_level	(default: empty)
       The  default SMTP TLS security level for	the Postfix SMTP client.  When
       a non-empty value is specified, this overrides the obsolete  parameters
       smtp_use_tls,  smtp_enforce_tls,	and smtp_tls_enforce_peername; when no
       value is	specified for smtp_tls_enforce_peername	or the obsolete	param-
       eters, the default SMTP TLS security level is none.

       Specify one of the following security levels:

       none   No  TLS. TLS will	not be used unless enabled for specific	desti-
	      nations via smtp_tls_policy_maps.

       may    Opportunistic TLS. Use TLS if this is supported  by  the	remote
	      SMTP server, otherwise use plaintext. Since sending in the clear
	      is acceptable, demanding	stronger  than	default	 TLS  security
	      merely  reduces  interoperability.   The	"smtp_tls_ciphers" and
	      "smtp_tls_protocols" (Postfix >= 2.6)  configuration  parameters
	      provide  control	over  the protocols and	cipher grade used with
	      opportunistic TLS.  With earlier releases	the opportunistic  TLS
	      cipher  grade  is	always "export"	and no protocols are disabled.
	      When TLS handshakes fail,	the connection	is  retried  with  TLS
	      disabled.	  This allows mail delivery to sites with non-interop-
	      erable TLS implementations.

       encrypt
	      Mandatory	TLS encryption.	Since a	minimum	level of  security  is
	      intended,	it is reasonable to be specific	about sufficiently se-
	      cure protocol versions and ciphers. At this security  level  and
	      higher,  the main.cf parameters smtp_tls_mandatory_protocols and
	      smtp_tls_mandatory_ciphers specify the TLS protocols and minimum
	      cipher grade which the administrator considers secure enough for
	      mandatory	encrypted sessions. This security level	is not an  ap-
	      propriate	default	for systems delivering mail to the Internet.

       dane   Opportunistic  DANE TLS.	At this	security level,	the TLS	policy
	      for the destination is obtained via DNSSEC.  For TLSA policy  to
	      be  in effect, the destination domain's containing DNS zone must
	      be signed	and the	Postfix	SMTP client's operating	system must be
	      configured to send its DNS queries to a recursive	DNS nameserver
	      that is able to validate the signed records.  Each MX host's DNS
	      zone  should  also  be signed, and should	publish	DANE TLSA (RFC
	      7672) records that specify how that MX host's TLS	certificate is
	      to  be verified.	TLSA records do	not preempt the	normal SMTP MX
	      host selection algorithm,	if some	MX hosts support TLSA and oth-
	      ers  do  not,  TLS security will vary from delivery to delivery.
	      It is up to the domain owner to configure	 their	MX  hosts  and
	      their  DNS  sensibly.   To configure the Postfix SMTP client for
	      DNSSEC lookups  see  the	documentation  for  the	 smtp_dns_sup-
	      port_level   main.cf   parameter.	  When	DNSSEC-validated  TLSA
	      records are not found the	effective tls security level is	"may".
	      When  TLSA records are found, but	are all	unusable the effective
	      security level is	"encrypt".  For	purposes of protocol  and  ci-
	      pher  selection,	the  "dane"  security  level is	treated	like a
	      "mandatory" TLS security level, and weak ciphers	and  protocols
	      are  disabled.  Since DANE authenticates server certificates the
	      "aNULL" cipher-suites are	transparently excluded at this	level,
	      no need to configure this	manually.  RFC 7672 (DANE) TLS authen-
	      tication is available with Postfix 2.11 and later.

       dane-only
	      Mandatory	DANE TLS.  This	is just	like "dane"  above,  but  DANE
	      TLSA  authentication is required.	 There is no fallback to "may"
	      or "encrypt" when	TLSA records are  missing  or  unusable.   RFC
	      7672  (DANE)  TLS	 authentication	is available with Postfix 2.11
	      and later.

       fingerprint
	      Certificate fingerprint verification.  At	this  security	level,
	      there are	no trusted Certification Authorities.  The certificate
	      trust chain, expiration date, etc., are  not  checked.  Instead,
	      the smtp_tls_fingerprint_cert_match parameter lists the certifi-
	      cate fingerprint or public  key  fingerprint  (Postfix  2.9  and
	      later)  of  the  valid  server certificate. The digest algorithm
	      used  to	calculate  the	fingerprint   is   selected   by   the
	      smtp_tls_fingerprint_digest  parameter.  Available  with Postfix
	      2.5 and later.

       verify Mandatory	TLS verification.  At  this  security  level,  DNS  MX
	      lookups  are  trusted to be secure enough, and the name verified
	      in the server certificate	is  usually  obtained  indirectly  via
	      unauthenticated  DNS  MX lookups.	The smtp_tls_verify_cert_match
	      parameter	controls how the server	name is	verified. In  practice
	      explicit	control	 over  matching	is more	common at the "secure"
	      level, described below. This security level is not an  appropri-
	      ate default for systems delivering mail to the Internet.

       secure Secure-channel  TLS.   At	 this  security	level, DNS MX lookups,
	      though potentially used  to  determine  the  candidate  next-hop
	      gateway  IP  addresses,  are not trusted to be secure enough for
	      TLS peername verification. Instead, the default name verified in
	      the  server  certificate is obtained from	the next-hop domain as
	      specified	in the smtp_tls_secure_cert_match configuration	param-
	      eter.  The  default  matching  rule is that a server certificate
	      matches when its name is equal to	or is a	sub-domain of the nex-
	      thop  domain.  This security level is not	an appropriate default
	      for systems delivering mail to the Internet.

       Examples:

       # No TLS. Formerly: smtp_use_tls=no and smtp_enforce_tls=no.
       smtp_tls_security_level = none

       # Opportunistic TLS.
       smtp_tls_security_level = may
       # Do not	tweak opportunistic ciphers or protocols unless	it is essential
       # to do so (if a	security vulnerability is found	in the SSL library that
       # can be	mitigated by disabling a particular protocol or	raising	the
       # cipher	grade).
       smtp_tls_ciphers	= medium
       smtp_tls_protocols = >=TLSv1
       # Legacy	(Postfix < 3.6)	syntax:
       smtp_tls_protocols = !SSLv2, !SSLv3

       # Mandatory (high-grade)	TLS encryption.
       smtp_tls_security_level = encrypt
       smtp_tls_mandatory_ciphers = high

       # Authenticated TLS 1.2 or better matching the nexthop domain or	a
       # subdomain.
       smtp_tls_security_level = secure
       smtp_tls_mandatory_ciphers = high
       smtp_tls_mandatory_protocols = >=TLSv1.2
       smtp_tls_secure_cert_match = nexthop, dot-nexthop

       # Certificate fingerprint verification (Postfix >= 2.5).
       # The CA-less "fingerprint" security level only scales to a limited
       # number	of destinations. As a global default rather than a per-site
       # setting, this is practical only when mail for all recipients is sent
       # to a central mail hub.
       relayhost = [mailhub.example.com]
       smtp_tls_security_level = fingerprint
       smtp_tls_mandatory_protocols = >=TLSv1.2
       smtp_tls_mandatory_ciphers = high
       smtp_tls_fingerprint_cert_match =
	   3D:95:34:51:...:40:99:C0:C1
	   EC:3B:2D:B0:...:A3:9D:72:F6

       This feature is available in Postfix 2.3	and later.

smtp_tls_servername (default: empty)
       Optional	name to	send to	the remote SMTP	server in the TLS Server  Name
       Indication  (SNI)  extension.  The SNI extension	is always on when DANE
       is used to authenticate the server, and in that case the	SNI name  sent
       is the one required by RFC7672 and this parameter is ignored.

       Some  SMTP  servers  use	the received SNI name to select	an appropriate
       certificate chain to present to the client.  While this may improve in-
       teroperability  with  such servers, it may reduce interoperability with
       other servers that choose to abort the connection when they don't  have
       a  certificate  chain  configured for the requested name.  Such servers
       should select a default certificate chain and continue  the  handshake,
       but  some  may not.  Therefore, absent DANE, no SNI name	is sent	by de-
       fault.

       The SNI name must be either a valid DNS hostname, or else  one  of  the
       special	values	hostname  or  nexthop,	which select either the	remote
       hostname	or the nexthop domain respectively.  DNS names for SNI must be
       in  A-label (punycode) form.  Invalid DNS names log a configuration er-
       ror warning and mail delivery is	deferred.

       Except when using a relayhost to	forward	all email, the	only  sensible
       non-empty  main.cf  setting  for	 this  parameter  is  hostname.	 Other
       non-empty values	are only practical on a	per-destination	basis via  the
       servername  attribute  of the Postfix TLS policy	table.	When in	doubt,
       leave this  parameter  empty,  and  configure  per-destination  SNI  as
       needed.

       This feature is available in Postfix 3.4	and later.

smtp_tls_session_cache_database	(default: empty)
       Name  of	 the file containing the optional Postfix SMTP client TLS ses-
       sion cache. Specify a database type that	supports enumeration, such  as
       btree or	sdbm; there is no need to support concurrent access.  The file
       is created if it	does not exist.	The smtp(8) daemon does	not  use  this
       parameter  directly,  rather the	cache is implemented indirectly	in the
       tlsmgr(8) daemon. This means that per-smtp-instance master.cf overrides
       of this parameter are not effective.  Note that each of the cache data-
       bases supported by tlsmgr(8) daemon: $smtpd_tls_session_cache_database,
       $smtp_tls_session_cache_database	  (and	with  Postfix  2.3  and	 later
       $lmtp_tls_session_cache_database), needs	to be stored separately. It is
       not  at	this  time possible to store multiple caches in	a single data-
       base.

       Note: dbm databases are not  suitable.  TLS  session  objects  are  too
       large.

       As  of version 2.5, Postfix no longer uses root privileges when opening
       this file. The file  should  now	 be  stored  under  the	 Postfix-owned
       data_directory. As a migration aid, an attempt to open the file under a
       non-Postfix directory is	redirected to  the  Postfix-owned  data_direc-
       tory, and a warning is logged.

       Example:

       smtp_tls_session_cache_database = btree:/var/lib/postfix/smtp_scache

       This feature is available in Postfix 2.2	and later.

smtp_tls_session_cache_timeout (default: 3600s)
       The  expiration	time of	Postfix	SMTP client TLS	session	cache informa-
       tion.  A	cache cleanup is performed periodically	 every	$smtp_tls_ses-
       sion_cache_timeout  seconds.  As	with $smtp_tls_session_cache_database,
       this parameter is implemented in	the  tlsmgr(8)	daemon	and  therefore
       per-smtp-instance master.cf overrides are not possible.

       As  of  Postfix 2.11 this setting cannot	exceed 100 days.  If set <= 0,
       session caching is disabled.  If	set to a positive value	 less  than  2
       minutes,	the minimum value of 2 minutes is used instead.

       Specify	a  non-zero  time  value  (an  integral	value plus an optional
       one-letter suffix that specifies	the time unit).	 Time units:  s	 (sec-
       onds),  m  (minutes), h (hours),	d (days), w (weeks).  The default time
       unit is s (seconds).

       This feature is available in Postfix 2.2	and later.

smtp_tls_trust_anchor_file (default: empty)
       Zero or more PEM-format files  with  trust-anchor  certificates	and/or
       public  keys.  If the parameter is not empty the	root CAs in CAfile and
       CApath are no longer trusted.  Rather, the  Postfix  SMTP  client  will
       only  trust  certificate-chains signed by one of	the trust-anchors con-
       tained in the chosen files.  The	 specified  trust-anchor  certificates
       and  public  keys  are  not  subject  to	 expiration,  and  need	not be
       (self-signed) root CAs.	They may, if desired, be intermediate certifi-
       cates.  Therefore, these	certificates also may be found "in the middle"
       of the trust chain presented by the remote SMTP	server,	 and  any  un-
       trusted issuing parent certificates will	be ignored.  Specify a list of
       pathnames separated by comma or whitespace.

       Whether specified in  main.cf,  or  on  a  per-destination  basis,  the
       trust-anchor  PEM file must be accessible to the	Postfix	SMTP client in
       the chroot jail if applicable.  The trust-anchor	 file  should  contain
       only certificates and public keys, no private key material, and must be
       readable	by the non-privileged $mail_owner user.	 This allows  destina-
       tions  to  be  bound  to	 a  set	of specific CAs	or public keys without
       trusting	the same CAs for all destinations.

       The main.cf parameter  supports	single-purpose	Postfix	 installations
       that  send  mail	 to  a	fixed  set  of	SMTP peers.  At	most sites, if
       trust-anchor files are used  at	all,  they  will  be  specified	 on  a
       per-destination	basis  via  the	"tafile" attribute of the "verify" and
       "secure"	levels in smtp_tls_policy_maps.

       The underlying mechanism	is in support of RFC 7672 (DANE	 TLSA),	 which
       defines	mechanisms for an SMTP client MTA to securely determine	server
       TLS certificates	via DNS.

       If you want your	trust anchors to be public keys, with OpenSSL you  can
       extract a single	PEM public key from a PEM X.509	file containing	a sin-
       gle certificate,	as follows:

	   $ openssl x509 -in cert.pem -out ta-key.pem -noout -pubkey

       This feature is available in Postfix 2.11 and later.

smtp_tls_verify_cert_match (default: hostname)
       How the Postfix SMTP client verifies the	 server	 certificate  peername
       for  the	 "verify"  TLS	security level.	In a "verify" TLS policy table
       ($smtp_tls_policy_maps) entry the optional "match" attribute  overrides
       this main.cf setting.

       This  parameter	specifies one or more patterns or strategies separated
       by commas, whitespace or	colons.	 In the	policy table  the  only	 valid
       separator is the	colon character.

       Patterns	specify	domain names, or domain	name suffixes:

       example.com
	      Match  the  example.com  domain,	i.e.  one  of the names	in the
	      server certificate must be example.com.  Upper  and  lower  case
	      distinctions are ignored.

       .example.com
	      Match subdomains of the example.com domain, i.e. match a name in
	      the server certificate that consists of a	non-zero number	of la-
	      bels  followed  by  a .example.com suffix. Case distinctions are
	      ignored.

       Strategies specify a transformation from	the next-hop domain to the ex-
       pected name in the server certificate:

       nexthop
	      Match against the	next-hop domain, which is either the recipient
	      domain, or the transport	next-hop  configured  for  the	domain
	      stripped	of  any	 optional socket type prefix, enclosing	square
	      brackets and trailing port. When MX lookups are not  suppressed,
	      this  is the original nexthop domain prior to the	MX lookup, not
	      the result of the	MX lookup. For LMTP delivery  via  UNIX-domain
	      sockets, the verified next-hop name is $myhostname.  This	strat-
	      egy is suitable for use with the "secure"	policy.	 Case  is  ig-
	      nored.

       dot-nexthop
	      As above,	but match server certificate names that	are subdomains
	      of the next-hop domain. Case is ignored.

       hostname
	      Match against the	hostname of the	server,	often obtained via  an
	      unauthenticated DNS MX lookup. For LMTP delivery via UNIX-domain
	      sockets, the verified name is $myhostname. This matches the ver-
	      ification	 strategy  of  the  "MUST"  keyword  in	 the  obsolete
	      smtp_tls_per_site	table, and is suitable for use with the	 "ver-
	      ify"  security  level.  When  the	 next-hop  name	is enclosed in
	      square brackets to suppress MX lookups, the "hostname"  strategy
	      is the same as the "nexthop" strategy. Case is ignored.

       Sample main.cf setting:

       smtp_tls_verify_cert_match = hostname, nexthop, dot-nexthop

       Sample policy table override:

       example.com     verify  match=hostname:nexthop
       .example.com    verify  match=example.com:.example.com:hostname

       This feature is available in Postfix 2.3	and later.

smtp_tls_wrappermode (default: no)
       Request	that  the  Postfix  SMTP  client  connects  using  the SUBMIS-
       SIONS/SMTPS protocol instead of using the STARTTLS command.

       This mode requires "smtp_tls_security_level = encrypt" or stronger.

       Example:	deliver	all remote mail	via a  provider's  server  "mail.exam-
       ple.com".

       /usr/local/etc/postfix/main.cf:
	   # Client-side SMTPS requires	"encrypt" or stronger.
	   smtp_tls_security_level = encrypt
	   smtp_tls_wrappermode	= yes
	   # The [] suppress MX	lookups.
	   relayhost = [mail.example.com]:465

       More  examples  are in TLS_README, including examples for older Postfix
       versions.

       This feature is available in Postfix 3.0	and later.

smtp_use_tls (default: no)
       Opportunistic mode: use TLS when	a remote SMTP server announces	START-
       TLS  support,  otherwise	 send the mail in the clear. Beware: some SMTP
       servers offer STARTTLS even if it is not	configured.   With  Postfix  <
       2.3,  if	the TLS	handshake fails, and no	other server is	available, de-
       livery is deferred and mail stays in the	queue. If this	is  a  concern
       for you,	use the	smtp_tls_per_site feature instead.

       This  feature  is  available in Postfix 2.2 and later. With Postfix 2.3
       and later use smtp_tls_security_level instead.

smtp_xforward_timeout (default:	300s)
       The Postfix SMTP	client time limit for sending  the  XFORWARD  command,
       and for receiving the remote SMTP server	response.

       Specify	a  non-zero  time  value  (an  integral	value plus an optional
       one-letter suffix that specifies	the time unit).	 Time units:  s	 (sec-
       onds),  m  (minutes), h (hours),	d (days), w (weeks).  The default time
       unit is s (seconds).

       This feature is available in Postfix 2.1	and later.

smtpd_authorized_verp_clients (default:	$authorized_verp_clients)
       What remote SMTP	clients	are allowed  to	 specify  the  XVERP  command.
       This  command  requests	that mail be delivered one recipient at	a time
       with a per recipient return address.

       By default, no clients are allowed to specify XVERP.

       This parameter was renamed with Postfix version 2.1. The	default	 value
       is backwards compatible with Postfix version 2.0.

       Specify	a list of network/netmask patterns, separated by commas	and/or
       whitespace. The mask specifies the number of bits in the	 network  part
       of a host address. You can also specify hostnames or .domain names (the
       initial	dot  causes  the  domain  to  match  any   name	  below	  it),
       "/file/name"  or	 "type:table" patterns.	 A "/file/name"	pattern	is re-
       placed by its contents; a "type:table" lookup table is matched  when  a
       table  entry  matches  a	 lookup	string (the lookup result is ignored).
       Continue	long lines by starting the next	line with whitespace.  Specify
       "!pattern"  to  exclude	an address or network block from the list. The
       form "!/file/name" is supported only in Postfix version 2.4 and later.

       Note: IP	version	6 address information must be specified	inside	[]  in
       the  smtpd_authorized_verp_clients  value,  and in files	specified with
       "/file/name".  IP version 6 addresses contain the  ":"  character,  and
       would otherwise be confused with	a "type:table" pattern.

smtpd_authorized_xclient_hosts (default: empty)
       What  remote SMTP clients are allowed to	use the	XCLIENT	feature.  This
       command overrides remote	SMTP client information	that is	used  for  ac-
       cess  control.  Typical	use  is	for SMTP-based content filters,	fetch-
       mail-like programs,  or	SMTP  server  access  rule  testing.  See  the
       XCLIENT_README document for details.

       This feature is available in Postfix 2.1	and later.

       By default, no clients are allowed to specify XCLIENT.

       Specify	a list of network/netmask patterns, separated by commas	and/or
       whitespace. The mask specifies the number of bits in the	 network  part
       of a host address. You can also specify hostnames or .domain names (the
       initial	dot  causes  the  domain  to  match  any   name	  below	  it),
       "/file/name"  or	 "type:table" patterns.	 A "/file/name"	pattern	is re-
       placed by its contents; a "type:table" lookup table is matched  when  a
       table  entry  matches  a	 lookup	string (the lookup result is ignored).
       Continue	long lines by starting the next	line with whitespace.  Specify
       "!pattern"  to  exclude	an address or network block from the list. The
       form "!/file/name" is supported only in Postfix version 2.4 and later.

       Note: IP	version	6 address information must be specified	inside	[]  in
       the  smtpd_authorized_xclient_hosts  value, and in files	specified with
       "/file/name".  IP version 6 addresses contain the  ":"  character,  and
       would otherwise be confused with	a "type:table" pattern.

smtpd_authorized_xforward_hosts	(default: empty)
       What remote SMTP	clients	are allowed to use the XFORWARD	feature.  This
       command forwards	information that is  used  to  improve	logging	 after
       SMTP-based  content  filters.  See the XFORWARD_README document for de-
       tails.

       This feature is available in Postfix 2.1	and later.

       By default, no clients are allowed to specify XFORWARD.

       Specify a list of network/netmask patterns, separated by	commas	and/or
       whitespace.  The	 mask specifies	the number of bits in the network part
       of a host address. You can also specify hostnames or .domain names (the
       initial	 dot   causes	the  domain  to	 match	any  name  below  it),
       "/file/name" or "type:table" patterns.  A "/file/name" pattern  is  re-
       placed  by  its contents; a "type:table"	lookup table is	matched	when a
       table entry matches a lookup string (the	 lookup	 result	 is  ignored).
       Continue	 long lines by starting	the next line with whitespace. Specify
       "!pattern" to exclude an	address	or network block from  the  list.  The
       form "!/file/name" is supported only in Postfix version 2.4 and later.

       Note:  IP  version 6 address information	must be	specified inside [] in
       the smtpd_authorized_xforward_hosts value, and in files specified  with
       "/file/name".   IP  version  6 addresses	contain	the ":"	character, and
       would otherwise be confused with	a "type:table" pattern.

smtpd_banner (default: $myhostname ESMTP $mail_name)
       The text	that follows the 220 status code in the	SMTP greeting  banner.
       Some  people like to see	the mail version advertised. By	default, Post-
       fix shows no version.

       You MUST	specify	$myhostname at the start of the	text. This is required
       by the SMTP protocol.

       Example:

       smtpd_banner = $myhostname ESMTP	$mail_name ($mail_version)

smtpd_client_auth_rate_limit (default: 0)
       The  maximal number of AUTH commands that any client is allowed to send
       to this service per time	unit, regardless of whether or not Postfix ac-
       tually  accepts	those  commands.   The time unit is specified with the
       anvil_rate_time_unit configuration parameter.

       By default, there is no limit on	the number of  AUTH  commands  that  a
       client may send.

       To disable this feature,	specify	a limit	of 0.

       WARNING:	 The purpose of	this feature is	to limit abuse.	It must	not be
       used to regulate	legitimate mail	traffic.

       This feature is available in Postfix 3.1	and later.

smtpd_client_connection_count_limit (default: 50)
       How many	simultaneous connections any client is allowed to make to this
       service.	  By  default,	the  limit  is set to half the default process
       limit value.

       To disable this feature,	specify	a limit	of 0.

       WARNING:	The purpose of this feature is to limit	abuse. It must not  be
       used to regulate	legitimate mail	traffic.

       This feature is available in Postfix 2.2	and later.

smtpd_client_connection_rate_limit (default: 0)
       The maximal number of connection	attempts any client is allowed to make
       to this service per time	unit.  The time	unit  is  specified  with  the
       anvil_rate_time_unit configuration parameter.

       By  default,  a	client	can  make as many connections per time unit as
       Postfix can accept.

       To disable this feature,	specify	a limit	of 0.

       WARNING:	The purpose of this feature is to limit	abuse. It must not  be
       used to regulate	legitimate mail	traffic.

       This feature is available in Postfix 2.2	and later.

       Example:

       smtpd_client_connection_rate_limit = 1000

smtpd_client_event_limit_exceptions (default: $mynetworks)
       Clients that are	excluded from smtpd_client_*_count/rate_limit restric-
       tions. See the mynetworks parameter description for the parameter value
       syntax.

       By default, clients in trusted networks are excluded. Specify a list of
       network blocks, hostnames or .domain names (the initial dot causes  the
       domain to match any name	below it).

       Note:  IP  version 6 address information	must be	specified inside [] in
       the smtpd_client_event_limit_exceptions value, and in  files  specified
       with  "/file/name".   IP	version	6 addresses contain the	":" character,
       and would otherwise be confused with a "type:table" pattern.

       Pattern matching	of domain names	is controlled by the presence  or  ab-
       sence   of   "smtpd_client_event_limit_exceptions"  in  the  parent_do-
       main_matches_subdomains parameter value (Postfix	3.0 and	later).

       This feature is available in Postfix 2.2	and later.

smtpd_client_message_rate_limit	(default: 0)
       The maximal number of message delivery requests that any	client is  al-
       lowed  to  make to this service per time	unit, regardless of whether or
       not Postfix actually accepts those messages.  The time unit  is	speci-
       fied with the anvil_rate_time_unit configuration	parameter.

       By  default,  a	client	can send as many message delivery requests per
       time unit as Postfix can	accept.

       To disable this feature,	specify	a limit	of 0.

       WARNING:	The purpose of this feature is to limit	abuse. It must not  be
       used to regulate	legitimate mail	traffic.

       This feature is available in Postfix 2.2	and later.

       Example:

       smtpd_client_message_rate_limit = 1000

smtpd_client_new_tls_session_rate_limit	(default: 0)
       The  maximal  number of new (i.e., uncached) TLS	sessions that a	remote
       SMTP client is allowed to negotiate with	this service  per  time	 unit.
       The  time unit is specified with	the anvil_rate_time_unit configuration
       parameter.

       By default, a remote SMTP client	can negotiate as many new TLS sessions
       per time	unit as	Postfix	can accept.

       To  disable  this  feature,  specify a limit of 0. Otherwise, specify a
       limit that is at	least the per-client concurrent	session	limit, or else
       legitimate client sessions may be rejected.

       WARNING:	 The purpose of	this feature is	to limit abuse.	It must	not be
       used to regulate	legitimate mail	traffic.

       This feature is available in Postfix 2.3	and later.

       Example:

       smtpd_client_new_tls_session_rate_limit = 100

smtpd_client_port_logging (default: no)
       Enable logging of the remote SMTP client	port in	addition to the	 host-
       name and	IP address. The	logging	format is "host[address]:port".

       This feature is available in Postfix 2.5	and later.

smtpd_client_recipient_rate_limit (default: 0)
       The maximal number of recipient addresses that any client is allowed to
       send to this service per	time unit, regardless of whether or not	 Post-
       fix actually accepts those recipients.  The time	unit is	specified with
       the anvil_rate_time_unit	configuration parameter.

       By default, a client can	send as	many recipient addresses per time unit
       as Postfix can accept.

       To disable this feature,	specify	a limit	of 0.

       WARNING:	 The purpose of	this feature is	to limit abuse.	It must	not be
       used to regulate	legitimate mail	traffic.

       This feature is available in Postfix 2.2	and later.

       Example:

       smtpd_client_recipient_rate_limit = 1000

smtpd_client_restrictions (default: empty)
       Optional	restrictions that the Postfix SMTP server applies in the  con-
       text  of	a client connection request.  See SMTPD_ACCESS_README, section
       "Delayed	evaluation of SMTP access restriction lists" for a  discussion
       of evaluation context and time.

       The default is to allow all connection requests.

       Specify	a list of restrictions,	separated by commas and/or whitespace.
       Continue	long lines by starting the next	 line  with  whitespace.   Re-
       strictions are applied in the order as specified; the first restriction
       that matches wins.

       The following restrictions are specific to client  hostname  or	client
       network address information.

       check_ccert_access type:table
	      By default use the remote	SMTP client certificate	fingerprint or
	      the public key fingerprint (Postfix 2.9 and later) as the	lookup
	      key  for	the specified access(5)	database; with Postfix version
	      2.2, also	require	that the remote	 SMTP  client  certificate  is
	      verified successfully.  The fingerprint digest algorithm is con-
	      figurable	  via	the   smtpd_tls_fingerprint_digest   parameter
	      (hard-coded  as md5 prior	to Postfix version 2.5).  This feature
	      requires "smtpd_tls_ask_ccert = yes" and is available with Post-
	      fix version 2.2 and later.
	      The default algorithm is sha256 with Postfix >= 3.6 and the com-
	      patibility_level set to 3.6 or higher. With Postfix <= 3.5,  the
	      default  algorithm  is  md5.  The	best-practice algorithm	is now
	      sha256. Recent advances in hash function cryptanalysis have  led
	      to  md5  and sha1	being deprecated in favor of sha256.  However,
	      as long as there are no known "second pre-image" attacks against
	      the older	algorithms, their use in this context, though not rec-
	      ommended,	is still likely	safe.
	      Alternatively, check_ccert_access	accepts	an explicit search or-
	      der  (Postfix  3.5  and  later). The default search order	as de-
	      scribed above corresponds	with:
	      check_ccert_access { type:table, { search_order  =  cert_finger-
	      print, pubkey_fingerprint	} }
	      The commas are optional.

       check_client_access type:table
	      Search  the  specified  access database for the client hostname,
	      parent domains, client  IP  address,  or	networks  obtained  by
	      stripping	 least	significant  octets.  See the access(5)	manual
	      page for details.

       check_client_a_access type:table
	      Search the specified access(5) database for the IP addresses for
	      the  client  hostname,  and  execute  the	 corresponding action.
	      Note: a result of	"OK" is	not allowed for	 safety	 reasons.  In-
	      stead,  use  DUNNO  in  order  to	 exclude  specific  hosts from
	      denylists.  This feature is available in Postfix 3.0 and later.

       check_client_mx_access type:table
	      Search the specified access(5) database for the MX hosts for the
	      client hostname, and execute the corresponding action.  If no MX
	      record is	found, look up A or AAAA records, just like the	 Post-
	      fix SMTP client would. Note: a result of "OK" is not allowed for
	      safety reasons. Instead, use DUNNO in order to exclude  specific
	      hosts  from denylists.  This feature is available	in Postfix 2.7
	      and later.

       check_client_ns_access type:table
	      Search the specified access(5) database for the DNS servers  for
	      the  client  hostname,  and  execute  the	 corresponding action.
	      Note: a result of	"OK" is	not allowed for	 safety	 reasons.  In-
	      stead,  use  DUNNO  in  order  to	 exclude  specific  hosts from
	      denylists.  This feature is available in Postfix 2.7 and later.

       check_reverse_client_hostname_access type:table
	      Search the specified access database for the unverified  reverse
	      client  hostname,	parent domains,	client IP address, or networks
	      obtained by stripping least  significant	octets.	 See  the  ac-
	      cess(5)  manual page for details.	 Note: a result	of "OK"	is not
	      allowed for safety reasons.  Instead, use	DUNNO in order to  ex-
	      clude  specific hosts from denylists.  This feature is available
	      in Postfix 2.6 and later.

       check_reverse_client_hostname_a_access type:table
	      Search the specified access(5) database for the IP addresses for
	      the  unverified  reverse client hostname,	and execute the	corre-
	      sponding action.	Note: a	result of  "OK"	 is  not  allowed  for
	      safety reasons.  Instead,	use DUNNO in order to exclude specific
	      hosts from denylists.  This feature is available in Postfix  3.0
	      and later.

       check_reverse_client_hostname_mx_access type:table
	      Search the specified access(5) database for the MX hosts for the
	      unverified reverse client	hostname, and execute the  correspond-
	      ing  action.   If	 no  MX	 record	 is  found,  look up A or AAAA
	      records, just like the Postfix SMTP client would.	 Note:	a  re-
	      sult  of	"OK"  is not allowed for safety	reasons.  Instead, use
	      DUNNO in order to	exclude	specific hosts from  denylists.	  This
	      feature is available in Postfix 2.7 and later.

       check_reverse_client_hostname_ns_access type:table
	      Search  the specified access(5) database for the DNS servers for
	      the unverified reverse client hostname, and execute  the	corre-
	      sponding	action.	  Note:	 a  result  of "OK" is not allowed for
	      safety reasons.  Instead,	use DUNNO in order to exclude specific
	      hosts  from denylists.  This feature is available	in Postfix 2.7
	      and later.

       check_sasl_access type:table
	      Use the remote SMTP client SASL user name	as the lookup key  for
	      the  specified  access(5)	 database. The lookup key has the form
	      "username@domainname" when the smtpd_sasl_local_domain parameter
	      value  is	 non-empty.   Unlike  the check_client_access feature,
	      check_sasl_access	does not perform matches of parent domains  or
	      IP  subnet  ranges.  This	feature	is available with Postfix ver-
	      sion 2.11	and later.

       permit_inet_interfaces
	      Permit the request when the client IP address matches  $inet_in-
	      terfaces.

       permit_mynetworks
	      Permit  the  request when	the client IP address matches any net-
	      work or network address listed in	 $mynetworks.

       permit_sasl_authenticated
	      Permit the request when the client is successfully authenticated
	      via the RFC 4954 (AUTH) protocol.

       permit_tls_all_clientcerts
	      Permit  the  request  when the remote SMTP client	certificate is
	      verified successfully.  This option must be used only if a  spe-
	      cial  CA issues the certificates and only	this CA	is listed as a
	      trusted CA. Otherwise, clients with  a  third-party  certificate
	      would  also be allowed to	relay.	Specify	"tls_append_default_CA
	      =	no" when the trusted CA	is specified with smtpd_tls_CAfile  or
	      smtpd_tls_CApath,	 to  prevent  Postfix  from appending the sys-
	      tem-supplied    default	 CAs.	  This	  feature     requires
	      "smtpd_tls_ask_ccert  =  yes" and	is available with Postfix ver-
	      sion 2.2 and later.

       permit_tls_clientcerts
	      Permit the request when the remote SMTP client certificate  fin-
	      gerprint	or  public  key	fingerprint (Postfix 2.9 and later) is
	      listed in	$relay_clientcerts.  The fingerprint digest  algorithm
	      is  configurable	via the	smtpd_tls_fingerprint_digest parameter
	      (hard-coded as md5 prior to Postfix version 2.5).	 This  feature
	      requires "smtpd_tls_ask_ccert = yes" and is available with Post-
	      fix version 2.2 and later.
	      The default algorithm is sha256 with Postfix >= 3.6 and the com-
	      patibility_level	set to 3.6 or higher. With Postfix <= 3.5, the
	      default algorithm	is md5.	 The best-practice  algorithm  is  now
	      sha256.  Recent advances in hash function	cryptanalysis have led
	      to md5 and sha1 being deprecated in favor	of  sha256.   However,
	      as long as there are no known "second pre-image" attacks against
	      the older	algorithms, their use in this context, though not rec-
	      ommended,	is still likely	safe.

       reject_rbl_client rbl_domain=d.d.d.d
	      Reject  the  request when	the reversed client network address is
	      listed with the A	record	"d.d.d.d"  under  rbl_domain  (Postfix
	      version 2.1 and later only).  Each "d" is	a number, or a pattern
	      inside "[]" that contains	one or more ";"-separated  numbers  or
	      number..number  ranges  (Postfix	version	2.8 and	later).	 If no
	      "=d.d.d.d" is specified, reject the request  when	 the  reversed
	      client network address is	listed with any	A record under rbl_do-
	      main.
	      The maps_rbl_reject_code parameter specifies the	response  code
	      for  rejected  requests  (default:   554), the default_rbl_reply
	      parameter	specifies the default server reply,  and  the  rbl_re-
	      ply_maps	parameter specifies tables with	server replies indexed
	      by rbl_domain.  This feature is available	 in  Postfix  2.0  and
	      later.

       permit_dnswl_client dnswl_domain=d.d.d.d
	      Accept  the  request when	the reversed client network address is
	      listed with the A	record "d.d.d.d" under dnswl_domain.  Each "d"
	      is  a number, or a pattern inside	"[]" that contains one or more
	      ";"-separated  numbers  or   number..number   ranges.    If   no
	      "=d.d.d.d"  is  specified,  accept the request when the reversed
	      client network  address  is  listed  with	 any  A	 record	 under
	      dnswl_domain.
	      For  safety,  permit_dnswl_client	 is  silently  ignored when it
	      would override reject_unauth_destination.	  The  result  is  DE-
	      FER_IF_REJECT  when  allowlist  lookup  fails.   This feature is
	      available	in Postfix 2.8 and later.

       reject_rhsbl_client rbl_domain=d.d.d.d
	      Reject the request when the client hostname is listed with the A
	      record "d.d.d.d" under rbl_domain	(Postfix version 2.1 and later
	      only).  Each "d" is a number, or a pattern inside	"[]" that con-
	      tains one	or more	";"-separated numbers or number..number	ranges
	      (Postfix version 2.8 and later).	If no "=d.d.d.d" is specified,
	      reject the request when the client hostname is listed with any A
	      record under rbl_domain. See the	reject_rbl_client  description
	      above for	additional RBL related configuration parameters.  This
	      feature is available in Postfix 2.0 and later; with Postfix ver-
	      sion  2.8	 and  later,  reject_rhsbl_reverse_client will usually
	      produce better results.

       permit_rhswl_client rhswl_domain=d.d.d.d
	      Accept the request when the client hostname is listed with the A
	      record "d.d.d.d" under rhswl_domain.  Each "d" is	a number, or a
	      pattern inside "[]" that contains	one or more ";"-separated num-
	      bers  or	number..number	ranges.	If no "=d.d.d.d" is specified,
	      accept the request when the client hostname is listed with any A
	      record under rhswl_domain.
	      Caution:	client	name allowlisting is fragile, since the	client
	      name lookup can fail due to temporary outages.  Client name  al-
	      lowlisting should	be used	only to	reduce false positives in e.g.
	      DNS-based	blocklists, and	not for	making access rule exceptions.
	      For safety, permit_rhswl_client  is  silently  ignored  when  it
	      would  override  reject_unauth_destination.   The	 result	is DE-
	      FER_IF_REJECT when allowlist  lookup  fails.   This  feature  is
	      available	in Postfix 2.8 and later.

       reject_rhsbl_reverse_client rbl_domain=d.d.d.d
	      Reject  the  request when	the unverified reverse client hostname
	      is listed	with the A record "d.d.d.d"  under  rbl_domain.	  Each
	      "d"  is  a number, or a pattern inside "[]" that contains	one or
	      more ";"-separated numbers  or  number..number  ranges.	If  no
	      "=d.d.d.d"  is specified,	reject the request when	the unverified
	      reverse client hostname  is  listed  with	 any  A	 record	 under
	      rbl_domain.  See the reject_rbl_client description above for ad-
	      ditional RBL related configuration parameters.  This feature  is
	      available	in Postfix 2.8 and later.

       reject_unknown_client_hostname	(with	Postfix	  <   2.3:  reject_un-
       known_client)
	      Reject the request when 1) the client IP	address->name  mapping
	      fails,  or  2)  the  name->address  mapping  fails,  or  3)  the
	      name->address mapping does not match the client IP address.
	      This is  a  stronger  restriction	 than  the  reject_unknown_re-
	      verse_client_hostname  feature, which triggers only under	condi-
	      tion 1) above.
	      The unknown_client_reject_code parameter specifies the  response
	      code  for	 rejected requests (default: 450). The reply is	always
	      450 in case the address->name or name->address lookup failed due
	      to a temporary problem.

       reject_unknown_reverse_client_hostname
	      Reject  the  request  when  the  client  IP  address  has	no ad-
	      dress->name mapping.
	      This   is	  a   weaker   restriction   than    the    reject_un-
	      known_client_hostname  feature, which requires not only that the
	      address->name and	name->address mappings exist,  but  also  that
	      the two mappings reproduce the client IP address.
	      The  unknown_client_reject_code parameter	specifies the response
	      code for rejected	requests (default: 450).  The reply is	always
	      450  in  case the	address->name lookup failed due	to a temporary
	      problem.
	      This feature is available	in Postfix 2.3 and later.

       In addition, you	can use	any of	the  following	generic	 restrictions.
       These restrictions are applicable in any	SMTP command context.

       check_policy_service servername
	      Query  the  specified policy server. See the SMTPD_POLICY_README
	      document for details. This feature is available in  Postfix  2.1
	      and later.

       defer  Defer  the  request. The client is told to try again later. This
	      restriction is useful at the end of a restriction	list, to  make
	      the default policy explicit.
	      The  defer_code  parameter  specifies the	SMTP server reply code
	      (default:	450).

       defer_if_permit
	      Defer the	request	if some	later restriction would	result	in  an
	      explicit	or  implicit  PERMIT  action.	This  is useful	when a
	      denylisting feature fails	due to a temporary problem.  This fea-
	      ture is available	in Postfix version 2.1 and later.

       defer_if_reject
	      Defer  the  request  if some later restriction would result in a
	      REJECT action.  This is  useful  when  an	 allowlisting  feature
	      fails  due to a temporary	problem.  This feature is available in
	      Postfix version 2.1 and later.

       permit Permit the request. This restriction is useful at	the end	 of  a
	      restriction list,	to make	the default policy explicit.

       reject_multi_recipient_bounce
	      Reject the request when the envelope sender is the null address,
	      and the message has multiple envelope recipients.	This usage has
	      rare  but	 legitimate  applications:  under  certain conditions,
	      multi-recipient mail that	was posted with	 the  DSN  option  NO-
	      TIFY=NEVER may be	forwarded with the null	sender address.
	      Note:  this  restriction	can  only  work	 reliably when used in
	      smtpd_data_restrictions or  smtpd_end_of_data_restrictions,  be-
	      cause  the total number of recipients is not known at an earlier
	      stage of the SMTP	conversation.  Use at the RCPT stage will only
	      reject the second	etc.  recipient.
	      The  multi_recipient_bounce_reject_code  parameter specifies the
	      response code for	rejected requests (default:  550).  This  fea-
	      ture is available	in Postfix 2.1 and later.

       reject_plaintext_session
	      Reject  the  request  when the connection	is not encrypted. This
	      restriction should not be	used  before  the  client  has	had  a
	      chance  to  negotiate  encryption	with the AUTH or STARTTLS com-
	      mands.
	      The plaintext_reject_code	parameter specifies the	response  code
	      for  rejected  requests (default:	 450).	This feature is	avail-
	      able in Postfix 2.3 and later.

       reject_unauth_pipelining
	      Reject the request when the client sends SMTP commands ahead  of
	      time where it is not allowed, or when the	client sends SMTP com-
	      mands ahead of time without knowing that Postfix	actually  sup-
	      ports  ESMTP  command pipelining.	This stops mail	from bulk mail
	      software that improperly uses ESMTP command pipelining in	 order
	      to speed up deliveries.
	      With  Postfix  2.6 and later, the	SMTP server sets a per-session
	      flag whenever it detects illegal pipelining, including pipelined
	      HELO or EHLO commands. The reject_unauth_pipelining feature sim-
	      ply tests	whether	the flag was set at any	point in  time	during
	      the session.
	      With older Postfix versions, reject_unauth_pipelining checks the
	      current status of	the input read queue, and  its	usage  is  not
	      recommended in contexts other than smtpd_data_restrictions.

       reject Reject  the  request. This restriction is	useful at the end of a
	      restriction list,	to make	the default policy explicit.  The  re-
	      ject_code	 configuration	parameter  specifies the response code
	      for rejected requests (default: 554).

       sleep seconds
	      Pause for	the specified number of	seconds	and proceed  with  the
	      next  restriction	in the list, if	any. This may stop zombie mail
	      when used	as:
	      /usr/local/etc/postfix/main.cf:
		  smtpd_client_restrictions =
		      sleep 1, reject_unauth_pipelining
		  smtpd_delay_reject = no
	      This feature is available	in Postfix 2.3.

       warn_if_reject
	      A	safety net for testing.	When "warn_if_reject" is placed	before
	      a	 reject-type  restriction,  access  table query, or check_pol-
	      icy_service query, this logs a "reject_warning" message  instead
	      of rejecting a request (when a reject-type restriction fails due
	      to a temporary error, this logs a	"reject_warning"  message  for
	      any  implicit "defer_if_permit" actions that would normally pre-
	      vent mail	from being accepted by some later access restriction).
	      This feature has no effect on defer_if_reject restrictions.

       Other restrictions that are valid in this context:

       o      SMTP  command specific restrictions that are described under the
	      smtpd_helo_restrictions, smtpd_sender_restrictions or  smtpd_re-
	      cipient_restrictions  parameters.	When helo, sender or recipient
	      restrictions are listed  under  smtpd_client_restrictions,  they
	      have  effect  only  with	"smtpd_delay_reject  =	yes",  so that
	      $smtpd_client_restrictions is evaluated at the time of the  RCPT
	      TO command.

       Example:

       smtpd_client_restrictions = permit_mynetworks, reject_unknown_client_hostname

smtpd_command_filter (default: empty)
       A  mechanism to transform commands from remote SMTP clients.  This is a
       last-resort tool	to work	around client commands that  break  interoper-
       ability	with the Postfix SMTP server.  Other uses involve fault	injec-
       tion to test Postfix's handling of invalid commands.

       Specify the name	of a "type:table" lookup table.	The search  string  is
       the  SMTP  command as received from the remote SMTP client, except that
       initial whitespace and the trailing <CR><LF> are	removed.   The	result
       value is	executed by the	Postfix	SMTP server.

       There is	no need	to use smtpd_command_filter for	the following cases:

       o      Use "resolve_numeric_domain = yes" to accept "user@ipaddress".

       o      Postfix already accepts the correct form "user@[ipaddress]". Use
	      virtual_alias_maps or canonical_maps to translate	these into do-
	      main names if necessary.

       o      Use "strict_rfc821_envelopes = no" to accept "RCPT TO:<User Name
	      _user@example.com__". Postfix will ignore	the "User  Name"  part
	      and deliver to the _user@example.com_ address.

       Examples	 of  problems that can be solved with the smtpd_command_filter
       feature:

       /usr/local/etc/postfix/main.cf:
	   smtpd_command_filter	= pcre:$config_directory/command_filter

       /usr/local/etc/postfix/command_filter:
	   # Work around clients that send malformed HELO commands.
	   /^HELO\s*$/ HELO domain.invalid

	   # Work around clients that send empty lines.
	   /^\s*$/     NOOP

	   # Work around clients that send RCPT	TO:<'user@domain'>.
	   # WARNING: do not lose the parameters that follow the address.
	   /^(RCPT\s+TO:\s*<)'([^[:space:]]+)'(>.*)/	 $1$2$3

	   # Append XVERP to MAIL FROM commands	to request VERP-style delivery.
	   # See VERP_README for more information on how to use	Postfix	VERP.
	   /^(MAIL\s+FROM:\s*<listname@example\.com>.*)/   $1 XVERP

	   # Bounce-never mail sink. Use notify_classes=bounce,resource,software
	   # to	send bounced mail to the postmaster (with message body removed).
	   /^(RCPT\s+TO:\s*<.*>.*)\s+NOTIFY=\S+(.*)/	 $1 NOTIFY=NEVER$2
	   /^(RCPT\s+TO:.*)/				 $1 NOTIFY=NEVER

       This feature is available in Postfix 2.7.

smtpd_data_restrictions	(default: empty)
       Optional	access restrictions that the Postfix SMTP  server  applies  in
       the context of the SMTP DATA command.  See SMTPD_ACCESS_README, section
       "Delayed	evaluation of SMTP access restriction lists" for a  discussion
       of evaluation context and time.

       This feature is available in Postfix 2.0	and later.

       Specify	a list of restrictions,	separated by commas and/or whitespace.
       Continue	long lines by starting the next	 line  with  whitespace.   Re-
       strictions are applied in the order as specified; the first restriction
       that matches wins.

       The following restrictions are valid in this context:

       o      Generic restrictions that	can be used in any SMTP	 command  con-
	      text, described under smtpd_client_restrictions.

       o      SMTP    command	 specific    restrictions    described	 under
	      smtpd_client_restrictions,	      smtpd_helo_restrictions,
	      smtpd_sender_restrictions	or smtpd_recipient_restrictions.

       o      However,	no  recipient  information is available	in the case of
	      multi-recipient mail. Acting on only one recipient would be mis-
	      leading,	 because  any  decision	 will  affect  all  recipients
	      equally. Acting on all recipients	would require a	possibly  very
	      large  amount  of	 memory,  and would also be misleading for the
	      reasons mentioned	before.

       Examples:

       smtpd_data_restrictions = reject_unauth_pipelining
       smtpd_data_restrictions = reject_multi_recipient_bounce

smtpd_delay_open_until_valid_rcpt (default: yes)
       Postpone	the start of an	SMTP mail transaction until a  valid  RCPT  TO
       command	is received. Specify "no" to create a mail transaction as soon
       as the Postfix SMTP server receives a valid MAIL	FROM command.

       With sites that reject lots of mail, the	default	 setting  reduces  the
       use  of	disk,  CPU and memory resources. The downside is that rejected
       recipients are logged with NOQUEUE instead of a	mail  transaction  ID.
       This complicates	the logfile analysis of	multi-recipient	mail.

       This feature is available in Postfix 2.3	and later.

smtpd_delay_reject (default: yes)
       Wait until the RCPT TO command before evaluating	$smtpd_client_restric-
       tions, $smtpd_helo_restrictions and $smtpd_sender_restrictions, or wait
       until the ETRN command before evaluating	$smtpd_client_restrictions and
       $smtpd_helo_restrictions.

       This feature is turned on by default because  some  clients  apparently
       mis-behave  when	 the  Postfix SMTP server rejects commands before RCPT
       TO.

       The default setting has one major benefit: it allows Postfix to log re-
       cipient	address	 information  when  rejecting a	client name/address or
       sender address, so that it is possible to find out whose	mail is	 being
       rejected.

smtpd_discard_ehlo_keyword_address_maps	(default: empty)
       Lookup tables, indexed by the remote SMTP client	address, with case in-
       sensitive lists of EHLO keywords	 (pipelining,  starttls,  auth,	 etc.)
       that  the  Postfix  SMTP	server will not	send in	the EHLO response to a
       remote SMTP client. See smtpd_discard_ehlo_keywords for	details.   The
       tables are not searched by hostname for robustness reasons.

       Specify zero or more "type:name"	lookup tables, separated by whitespace
       or comma. Tables	will be	searched in the	specified order	until a	 match
       is found.

       This feature is available in Postfix 2.2	and later.

smtpd_discard_ehlo_keywords (default: empty)
       A  case	insensitive list of EHLO keywords (pipelining, starttls, auth,
       etc.) that the Postfix SMTP server will not send	in the	EHLO  response
       to a remote SMTP	client.

       This feature is available in Postfix 2.2	and later.

       Notes:

       o      Specify the silent-discard pseudo	keyword	to prevent this	action
	      from being logged.

       o      Use the smtpd_discard_ehlo_keyword_address_maps feature to  dis-
	      card EHLO	keywords selectively.

smtpd_dns_reply_filter (default: empty)
       Optional	 filter	 for  Postfix  SMTP  server  DNS  lookup results.  See
       smtp_dns_reply_filter for details including an example.

       This feature is available in Postfix 3.0	and later.

smtpd_end_of_data_restrictions (default: empty)
       Optional	access restrictions that the Postfix SMTP  server  applies  in
       the  context of the SMTP	END-OF-DATA command.  See SMTPD_ACCESS_README,
       section "Delayed	evaluation of SMTP access  restriction	lists"	for  a
       discussion of evaluation	context	and time.

       This feature is available in Postfix 2.2	and later.

       See smtpd_data_restrictions for details and limitations.

smtpd_enforce_tls (default: no)
       Mandatory  TLS:	announce  STARTTLS support to remote SMTP clients, and
       require that clients use	TLS encryption.	 According to  RFC  2487  this
       MUST NOT	be applied in case of a	publicly-referenced SMTP server.  This
       option is therefore off by default.

       Note 1: "smtpd_enforce_tls = yes" implies "smtpd_tls_auth_only =	yes".

       Note 2: when invoked via	 "sendmail  -bs",  Postfix  will  never	 offer
       STARTTLS	 due  to  insufficient privileges to access the	server private
       key. This is intended behavior.

       This feature is available in Postfix 2.2	and later.  With  Postfix  2.3
       and later use smtpd_tls_security_level instead.

smtpd_error_sleep_time (default: 1s)
       With  Postfix version 2.1 and later: the	SMTP server response delay af-
       ter a client has	made more  than	 $smtpd_soft_error_limit  errors,  and
       fewer than $smtpd_hard_error_limit errors, without delivering mail.

       With  Postfix  version  2.0  and	 earlier: the SMTP server delay	before
       sending a reject	(4xx or	5xx) response, when the	client has made	 fewer
       than  $smtpd_soft_error_limit  errors without delivering	mail. When the
       client has made $smtpd_soft_error_limit or more errors, delay  all  re-
       sponses	with  the  larger  of (number of errors) seconds or $smtpd_er-
       ror_sleep_time.

       Specify a non-negative time value (an integral value plus  an  optional
       one-letter  suffix  that	specifies the time unit).  Time	units: s (sec-
       onds), m	(minutes), h (hours), d	(days),	w (weeks).  The	 default  time
       unit is s (seconds).

smtpd_etrn_restrictions	(default: empty)
       Optional	 restrictions that the Postfix SMTP server applies in the con-
       text of a client	ETRN command.  See SMTPD_ACCESS_README,	 section  "De-
       layed  evaluation of SMTP access	restriction lists" for a discussion of
       evaluation context and time.

       The Postfix ETRN	implementation accepts only destinations that are eli-
       gible  for  the	Postfix	"fast flush" service. See the ETRN_README file
       for details.

       Specify a list of restrictions, separated by commas and/or  whitespace.
       Continue	 long  lines  by  starting the next line with whitespace.  Re-
       strictions are applied in the order as specified; the first restriction
       that matches wins.

       The  following restrictions are specific	to the domain name information
       received	with the ETRN command.

       check_etrn_access type:table
	      Search the specified access database for the ETRN	domain name or
	      its parent domains. See the access(5) manual page	for details.

       Other restrictions that are valid in this context:

       o      Generic  restrictions  that can be used in any SMTP command con-
	      text, described under smtpd_client_restrictions.

       o      SMTP   command	specific    restrictions    described	 under
	      smtpd_client_restrictions	and smtpd_helo_restrictions.

       Example:

       smtpd_etrn_restrictions = permit_mynetworks, reject

smtpd_expansion_filter (default: see postconf -d output)
       What characters are allowed in $name expansions of RBL reply templates.
       Characters not in the allowed set are replaced by "_".  Use C like  es-
       capes to	specify	special	characters such	as whitespace.

       The  smtpd_expansion_filter  value is not subject to Postfix configura-
       tion parameter $name expansion.

       This feature is available in Postfix 2.0	and later.

smtpd_forbidden_commands (default: CONNECT  GET	 POST  regexp:{{/^[^A-Z]/  Bo-
       gus}})
       List of commands	that cause the Postfix SMTP server to immediately ter-
       minate the session with a 221 code. This	 can  be  used	to  disconnect
       clients	that obviously attempt to abuse	the system. In addition	to the
       commands	listed in this parameter, commands that	 follow	 the  "Label:"
       format  of  message  headers will also cause a disconnect. With Postfix
       versions	3.6 and	earlier, the default value is "CONNECT GET POST".

       This feature is available in Postfix 2.2	and later.

       Support for inline regular expressions was  added  in  Postfix  version
       3.7. See	regexp_table(5)	for a description of the syntax	and features.

smtpd_hard_error_limit (default: normal: 20, overload: 1)
       The  maximal  number  of	errors a remote	SMTP client is allowed to make
       without delivering mail.	The Postfix SMTP server	disconnects  when  the
       limit  is reached. Normally the default limit is	20, but	it changes un-
       der overload to just 1. With Postfix 2.5	and earlier, the  SMTP	server
       always  allows  up  to  20 errors by default.  Valid values are greater
       than zero.

smtpd_helo_required (default: no)
       Require that a remote SMTP client introduces itself with	 the  HELO  or
       EHLO command before sending the MAIL command or other commands that re-
       quire EHLO negotiation.

       Example:

       smtpd_helo_required = yes

smtpd_helo_restrictions	(default: empty)
       Optional	restrictions that the Postfix SMTP server applies in the  con-
       text  of	 a client HELO command.	 See SMTPD_ACCESS_README, section "De-
       layed evaluation	of SMTP	access restriction lists" for a	discussion  of
       evaluation context and time.

       The default is to permit	everything.

       Note:  specify  "smtpd_helo_required  =	yes" to	fully enforce this re-
       striction (without "smtpd_helo_required = yes",	a  client  can	simply
       skip smtpd_helo_restrictions by not sending HELO	or EHLO).

       Specify	a list of restrictions,	separated by commas and/or whitespace.
       Continue	long lines by starting the next	 line  with  whitespace.   Re-
       strictions are applied in the order as specified; the first restriction
       that matches wins.

       The following restrictions are specific to the hostname information re-
       ceived with the HELO or EHLO command.

       check_helo_access type:table
	      Search  the  specified  access(5)	 database for the HELO or EHLO
	      hostname or parent domains, and execute  the  corresponding  ac-
	      tion.   Note:  specify  "smtpd_helo_required = yes" to fully en-
	      force this restriction (without "smtpd_helo_required =  yes",  a
	      client  can simply skip check_helo_access	by not sending HELO or
	      EHLO).

       check_helo_a_access type:table
	      Search the specified access(5) database for the IP addresses for
	      the HELO or EHLO hostname, and execute the corresponding action.
	      Note 1: a	result of "OK" is not allowed for safety reasons.  In-
	      stead,  use  DUNNO  in  order  to	 exclude  specific  hosts from
	      denylists.  Note 2: specify "smtpd_helo_required = yes" to fully
	      enforce this restriction (without	"smtpd_helo_required = yes", a
	      client can simply	skip check_helo_a_access by not	 sending  HELO
	      or EHLO).	 This feature is available in Postfix 3.0 and later.

       check_helo_mx_access type:table
	      Search the specified access(5) database for the MX hosts for the
	      HELO or EHLO hostname, and execute the corresponding action.  If
	      no  MX record is found, look up A	or AAAA	records, just like the
	      Postfix SMTP client would.  Note 1: a result of "OK" is not  al-
	      lowed for	safety reasons.	Instead, use DUNNO in order to exclude
	      specific hosts from denylists.  Note 2: specify  "smtpd_helo_re-
	      quired  =	 yes"  to  fully  enforce  this	 restriction  (without
	      "smtpd_helo_required  =  yes",  a	  client   can	 simply	  skip
	      check_helo_mx_access by not sending HELO or EHLO).  This feature
	      is available in Postfix 2.1 and later.

       check_helo_ns_access type:table
	      Search the specified access(5) database for the DNS servers  for
	      the HELO or EHLO hostname, and execute the corresponding action.
	      Note 1: a	result of "OK" is not allowed for safety reasons.  In-
	      stead,  use  DUNNO  in  order  to	 exclude  specific  hosts from
	      denylists.  Note 2: specify "smtpd_helo_required = yes" to fully
	      enforce this restriction (without	"smtpd_helo_required = yes", a
	      client can simply	skip check_helo_ns_access by not sending  HELO
	      or EHLO).	This feature is	available in Postfix 2.1 and later.

       reject_invalid_helo_hostname  (with Postfix < 2.3: reject_invalid_host-
       name)
	      Reject the request when the HELO or EHLO hostname	is  malformed.
	      Note:  specify "smtpd_helo_required = yes" to fully enforce this
	      restriction (without "smtpd_helo_required	= yes",	a  client  can
	      simply  skip reject_invalid_helo_hostname	by not sending HELO or
	      EHLO).
	      The invalid_hostname_reject_code specifies the response code for
	      rejected requests	(default: 501).

       reject_non_fqdn_helo_hostname	 (with	   Postfix    <	   2.3:	   re-
       ject_non_fqdn_hostname)
	      Reject the request when the HELO or  EHLO	 hostname  is  not  in
	      fully-qualified  domain  or address literal form,	as required by
	      the RFC. Note: specify "smtpd_helo_required = yes" to fully  en-
	      force  this  restriction (without	"smtpd_helo_required = yes", a
	      client can  simply  skip	reject_non_fqdn_helo_hostname  by  not
	      sending HELO or EHLO).
	      The  non_fqdn_reject_code	 parameter specifies the response code
	      for rejected requests (default: 504).

       reject_rhsbl_helo rbl_domain=d.d.d.d
	      Reject the request when the HELO or EHLO hostname	is listed with
	      the A record "d.d.d.d" under rbl_domain (Postfix version 2.1 and
	      later only).  Each "d" is	a number, or  a	 pattern  inside  "[]"
	      that  contains one or more ";"-separated numbers or number..num-
	      ber ranges (Postfix version 2.8 and later).  If no "=d.d.d.d" is
	      specified,  reject the request when the HELO or EHLO hostname is
	      listed  with  any	 A  record  under  rbl_domain.	See  the   re-
	      ject_rbl_client  description for additional RBL related configu-
	      ration parameters.  Note:	specify	"smtpd_helo_required = yes" to
	      fully  enforce  this restriction (without	"smtpd_helo_required =
	      yes", a client can simply	skip reject_rhsbl_helo by not  sending
	      HELO  or	EHLO).	This  feature  is available in Postfix 2.0 and
	      later.

       reject_unknown_helo_hostname (with Postfix < 2.3:  reject_unknown_host-
       name)
	      Reject  the  request when	the HELO or EHLO hostname has no DNS A
	      or MX record.
	      The reply	is specified with the unknown_hostname_reject_code pa-
	      rameter  (default: 450) or unknown_helo_hostname_tempfail_action
	      (default:	defer_if_permit).  See the  respective	parameter  de-
	      scriptions for details.
	      Note:  specify "smtpd_helo_required = yes" to fully enforce this
	      restriction (without "smtpd_helo_required	= yes",	a  client  can
	      simply  skip reject_unknown_helo_hostname	by not sending HELO or
	      EHLO).

       Other restrictions that are valid in this context:

       o      Generic restrictions that	can be used in any SMTP	 command  con-
	      text, described under smtpd_client_restrictions.

       o      Client  hostname	or  network  address specific restrictions de-
	      scribed under smtpd_client_restrictions.

       o      SMTP   command	specific    restrictions    described	 under
	      smtpd_sender_restrictions	or smtpd_recipient_restrictions.  When
	      sender or	recipient restrictions are listed under	smtpd_helo_re-
	      strictions,  they	 have  effect  only with "smtpd_delay_reject =
	      yes", so that $smtpd_helo_restrictions is	evaluated at the  time
	      of the RCPT TO command.

       Examples:

       smtpd_helo_restrictions = permit_mynetworks, reject_invalid_helo_hostname
       smtpd_helo_restrictions = permit_mynetworks, reject_unknown_helo_hostname

smtpd_history_flush_threshold (default:	100)
       The  maximal number of lines in the Postfix SMTP	server command history
       before it is flushed upon receipt of EHLO, RSET,	or end of DATA.

smtpd_junk_command_limit (default: normal: 100,	overload: 1)
       The number of junk commands (NOOP, VRFY,	ETRN or	RSET)  that  a	remote
       SMTP client can send before the Postfix SMTP server starts to increment
       the error counter with each junk	command.  The junk  command  count  is
       reset after mail	is delivered.  See also	the smtpd_error_sleep_time and
       smtpd_soft_error_limit configuration parameters.	 Normally the  default
       limit is	100, but it changes under overload to just 1. With Postfix 2.5
       and earlier, the	SMTP server always allows up to	100 junk  commands  by
       default.

smtpd_log_access_permit_actions	(default: empty)
       Enable  logging	of  the	 named	"permit" actions in SMTP server	access
       lists (by default, the SMTP server logs "reject"	actions	but not	 "per-
       mit"  actions).	 This feature does not affect conditional actions such
       as "defer_if_permit".

       Specify a list of "permit" action names,	"/file/name"  or  "type:table"
       patterns,  separated  by	 commas	and/or whitespace. The list is matched
       left to right, and the search stops on the first	match. A  "/file/name"
       pattern	is  replaced  by  its contents;	a "type:table" lookup table is
       matched when a name matches a lookup key	 (the  lookup  result  is  ig-
       nored).	Continue long lines by starting	the next line with whitespace.
       Specify "!pattern" to exclude a name from the list.

       Examples:

       /usr/local/etc/postfix/main.cf:
	   # Log all "permit" actions.
	   smtpd_log_access_permit_actions = static:all

       /usr/local/etc/postfix/main.cf:
	   # Log "permit_dnswl_client" only.
	   smtpd_log_access_permit_actions = permit_dnswl_client

       This feature is available in Postfix 2.10 and later.

smtpd_milter_maps (default: empty)
       Lookup tables with Milter settings per remote SMTP client  IP  address.
       The lookup result overrides the smtpd_milters setting, and has the same
       syntax.

       Note: lookup tables cannot return empty responses. Specify a lookup re-
       sult  of	DISABLE	(case does not matter) to indicate that	Milter support
       should be disabled.

       Example to disable Milters for local clients:

       /usr/local/etc/postfix/main.cf:
	   smtpd_milter_maps = cidr:$config_directory/smtpd_milter_map
	   smtpd_milters = inet:host:port, { inet:host:port, ... }, ...

       /usr/local/etc/postfix/smtpd_milter_map:
	   # Disable Milters for local clients.
	   127.0.0.0/8	  DISABLE
	   192.168.0.0/16 DISABLE
	   ::/64	  DISABLE
	   2001:db8::/32  DISABLE

       This feature is available in Postfix 3.2	and later.

smtpd_milters (default:	empty)
       A list of Milter	(mail filter) applications for new mail	 that  arrives
       via  the	 Postfix smtpd(8) server. Specify space	or comma as separator.
       See the MILTER_README document for details.

       This feature is available in Postfix 2.3	and later.

smtpd_min_data_rate (default: 500)
       The minimum plaintext data transfer rate	in bytes/second	for  DATA  and
       BDAT  requests, when deadlines are enabled with smtpd_per_request_dead-
       line. After a read operation transfers N	plaintext message bytes	 (pos-
       sibly  after  TLS decryption), and after	the DATA or BDAT request dead-
       line is decremented by the elapsed time of  that	 read  operation,  the
       DATA  or	 BDAT request deadline is incremented by N/smtpd_min_data_rate
       seconds.	However, the deadline will never  be  incremented  beyond  the
       time limit specified with smtpd_timeout.

       This feature is available in Postfix 3.7	and later.

smtpd_noop_commands (default: empty)
       List of commands	that the Postfix SMTP server replies to	with "250 Ok",
       without doing any syntax	checks and without changing state.  This  list
       overrides any commands built into the Postfix SMTP server.

smtpd_null_access_lookup_key (default: <>)
       The  lookup key to be used in SMTP access(5) tables instead of the null
       sender address.

smtpd_peername_lookup (default:	yes)
       Attempt to look up the remote SMTP client hostname, and verify that the
       name  matches  the client IP address. A client name is set to "unknown"
       when it cannot be looked	up or verified,	or when	name  lookup  is  dis-
       abled.	Turning	 off  name lookup reduces delays due to	DNS lookup and
       increases the maximal inbound delivery rate.

       This feature is available in Postfix 2.3	and later.

smtpd_per_record_deadline (default: normal: no,	overload: yes)
       Change the behavior of  the  smtpd_timeout  and	smtpd_starttls_timeout
       time limits, from a time	limit per read or write	system call, to	a time
       limit to	send or	receive	a complete record (an SMTP command line,  SMTP
       response	 line,	SMTP  message  content line, or	TLS protocol message).
       This limits the impact from hostile peers that trickle data one byte at
       a time.

       Note:  when per-record deadlines	are enabled, a short timeout may cause
       problems	with TLS over very slow	network	connections.  The reasons  are
       that  a	TLS protocol message can be up to 16 kbytes long (with TLSv1),
       and that	an entire TLS protocol message must be sent or received	within
       the per-record deadline.

       This  feature  is  available in Postfix 2.9-3.6.	With older Postfix re-
       leases, the behavior is as if this parameter is set  to	"no".  Postfix
       3.7 and later use smtpd_per_request_deadline.

smtpd_per_request_deadline (default: normal: no, overload: yes)
       Change  the  behavior  of  the smtpd_timeout and	smtpd_starttls_timeout
       time limits, from a time	limit per plaintext or TLS read	or write call,
       to  a combined time limit for receiving a complete SMTP request and for
       sending a complete SMTP response. The deadline  limits  only  the  time
       spent  waiting for plaintext or TLS read	or write calls,	not time spent
       elsewhere. The per-request deadline  limits  the	 impact	 from  hostile
       peers that trickle data one byte	at a time.

       See  smtpd_min_data_rate	 for  how  the per-request deadline is managed
       during the DATA and BDAT	phase.

       Note: when per-request deadlines	are enabled, a short  time  limit  may
       cause  problems with TLS	over very slow network connections. The	reason
       is that a TLS protocol message can  be  up  to  16  kbytes  long	 (with
       TLSv1),	and  that  an  entire TLS protocol message must	be transferred
       within the per-request deadline.

       This feature is available in Postfix 3.7	and later. A  weaker  feature,
       called  smtpd_per_record_deadline,  is  available with Postfix 2.9-3.6.
       With older Postfix releases, the	behavior is as if  this	 parameter  is
       set to "no".

       This feature is available in Postfix 3.7	and later.

smtpd_policy_service_default_action  (default:	451 4.3.5 Server configuration
       problem)
       The default action when an SMTPD	policy service request fails.  Specify
       "DUNNO"	to  behave  as if the failed  SMTPD policy service request was
       not sent, and to	continue processing other access restrictions, if any.

       Limitations:

       o      This parameter may specify any value that	would be a valid SMTPD
	      policy server response (or access(5) map lookup result).	An ac-
	      cess(5) map or policy server in this parameter value may need to
	      be declared in advance with a restriction_class setting.

       o      If the specified action invokes another check_policy_service re-
	      quest, that request will have the	built-in default action.

       This feature is available in Postfix 3.0	and later.

smtpd_policy_service_max_idle (default:	300s)
       The time	after which an idle SMTPD policy service connection is closed.

       Specify a non-zero time value  (an  integral  value  plus  an  optional
       one-letter  suffix  that	specifies the time unit).  Time	units: s (sec-
       onds), m	(minutes), h (hours), d	(days),	w (weeks).  The	 default  time
       unit is s (seconds).

       This feature is available in Postfix 2.1	and later.

smtpd_policy_service_max_ttl (default: 1000s)
       The  time  after	 which	an  active  SMTPD policy service connection is
       closed.

       Specify a non-zero time value  (an  integral  value  plus  an  optional
       one-letter  suffix  that	specifies the time unit).  Time	units: s (sec-
       onds), m	(minutes), h (hours), d	(days),	w (weeks).  The	 default  time
       unit is s (seconds).

       This feature is available in Postfix 2.1	and later.

smtpd_policy_service_policy_context (default: empty)
       Optional	 information  that  the	 Postfix  SMTP server specifies	in the
       "policy_context"	attribute of a policy service request (originally,  to
       share  the  same	 service  endpoint among multiple check_policy_service
       clients).

       This feature is available in Postfix 3.1	and later.

smtpd_policy_service_request_limit (default: 0)
       The maximal number of requests per SMTPD	policy service connection,  or
       zero  (no  limit). Once a connection reaches this limit,	the connection
       is closed and the next request will be sent over	a new connection. This
       is a workaround to avoid	error-recovery delays with policy servers that
       cannot maintain a persistent connection.

       This feature is available in Postfix 3.0	and later.

smtpd_policy_service_retry_delay (default: 1s)
       The delay between attempts to resend a failed SMTPD policy service  re-
       quest. Specify a	value greater than zero.

       Specify	a  non-zero  time  value  (an  integral	value plus an optional
       one-letter suffix that specifies	the time unit).	 Time units:  s	 (sec-
       onds),  m  (minutes), h (hours),	d (days), w (weeks).  The default time
       unit is s (seconds).

       This feature is available in Postfix 3.0	and later.

smtpd_policy_service_timeout (default: 100s)
       The time	limit for connecting to, writing to, or	receiving from a dele-
       gated SMTPD policy server.

       Specify	a  non-zero  time  value  (an  integral	value plus an optional
       one-letter suffix that specifies	the time unit).	 Time units:  s	 (sec-
       onds),  m  (minutes), h (hours),	d (days), w (weeks).  The default time
       unit is s (seconds).

       This feature is available in Postfix 2.1	and later.

smtpd_policy_service_try_limit (default: 2)
       The maximal number of attempts to send an SMTPD policy service  request
       before giving up. Specify a value greater than zero.

       This feature is available in Postfix 3.0	and later.

smtpd_proxy_ehlo (default: $myhostname)
       How  the	 Postfix SMTP server announces itself to the proxy filter.  By
       default,	the Postfix hostname is	used.

       This feature is available in Postfix 2.1	and later.

smtpd_proxy_filter (default: empty)
       The hostname and	TCP port of the	 mail  filtering  proxy	 server.   The
       proxy  receives	all mail from the Postfix SMTP server, and is supposed
       to give the result to another Postfix SMTP server process.

       Specify	"host:port"  or	 "inet:host:port"  for	a  TCP	endpoint,   or
       "unix:pathname"	for  a UNIX-domain endpoint. The host can be specified
       as an IP	address	or as a	symbolic name; no MX lookups are  done.	  When
       no "host" or "host:" is specified, the local machine is assumed.	 Path-
       name interpretation is relative to the Postfix queue directory.

       This feature is available in Postfix 2.1	and later.

       The "inet:" and "unix:" prefixes	 are  available	 in  Postfix  2.3  and
       later.

smtpd_proxy_options (default: empty)
       List  of	 options that control how the Postfix SMTP server communicates
       with a before-queue content filter. Specify zero	or more	of the follow-
       ing, separated by comma or whitespace.

       speed_adjust
	      Do  not connect to a before-queue	content	filter until an	entire
	      message has been received. This reduces the number of simultane-
	      ous before-queue content filter processes.

       NOTE  1:	A filter must not selectively reject recipients	of a multi-re-
       cipient message.	 Rejecting all recipients is OK, as is	accepting  all
       recipients.

       NOTE  2:	 This feature increases	the minimum amount of free queue space
       by $message_size_limit. The extra space is needed to save  the  message
       to a temporary file.

       This feature is available in Postfix 2.7	and later.

smtpd_proxy_timeout (default: 100s)
       The  time limit for connecting to a proxy filter	and for	sending	or re-
       ceiving information.  When a connection fails the client	gets a generic
       error  message while more detailed information is logged	to the maillog
       file.

       Specify a non-zero time value  (an  integral  value  plus  an  optional
       one-letter  suffix  that	specifies the time unit).  Time	units: s (sec-
       onds), m	(minutes), h (hours), d	(days),	w (weeks).  The	 default  time
       unit is s (seconds).

       This feature is available in Postfix 2.1	and later.

smtpd_recipient_limit (default:	1000)
       The  maximal  number of recipients that the Postfix SMTP	server accepts
       per message delivery request.

smtpd_recipient_overshoot_limit	(default: 1000)
       The number of recipients	that a remote SMTP client can send  in	excess
       of  the limit specified with $smtpd_recipient_limit, before the Postfix
       SMTP server increments the per-session error count for each excess  re-
       cipient.

smtpd_recipient_restrictions (default: see postconf -d output)
       Optional	 restrictions that the Postfix SMTP server applies in the con-
       text of a client	RCPT TO	command, after smtpd_relay_restrictions.   See
       SMTPD_ACCESS_README,  section  "Delayed	evaluation  of SMTP access re-
       striction lists"	for a discussion of evaluation context and time.

       With Postfix versions before 2.10, the rules for	relay  permission  and
       spam blocking were combined under smtpd_recipient_restrictions, result-
       ing in error-prone configuration.  As of	Postfix	2.10, relay permission
       rules are preferably implemented	with smtpd_relay_restrictions, so that
       a permissive spam blocking  policy  under  smtpd_recipient_restrictions
       will no longer result in	a permissive mail relay	policy.

       For  backwards  compatibility, sites that migrate from Postfix versions
       before 2.10 can set smtpd_relay_restrictions to the  empty  value,  and
       use smtpd_recipient_restrictions	exactly	as before.

       IMPORTANT:  Either  the	smtpd_relay_restrictions  or the smtpd_recipi-
       ent_restrictions	parameter must specify at least	one of	the  following
       restrictions. Otherwise Postfix will refuse to receive mail:

	   reject, reject_unauth_destination

	   defer, defer_if_permit, defer_unauth_destination

       Specify	a list of restrictions,	separated by commas and/or whitespace.
       Continue	long lines by starting the next	 line  with  whitespace.   Re-
       strictions are applied in the order as specified; the first restriction
       that matches wins.

       The following restrictions are specific to the recipient	 address  that
       is received with	the RCPT TO command.

       check_recipient_access type:table
	      Search the specified access(5) database for the resolved RCPT TO
	      address, domain, parent domains, or localpart@, and execute  the
	      corresponding action.

       check_recipient_a_access	type:table
	      Search the specified access(5) database for the IP addresses for
	      the RCPT TO domain, and execute the corresponding	action.	 Note:
	      a	result of "OK" is not allowed for safety reasons. Instead, use
	      DUNNO in order to	exclude	specific hosts from  denylists.	  This
	      feature is available in Postfix 3.0 and later.

       check_recipient_mx_access type:table
	      Search the specified access(5) database for the MX hosts for the
	      RCPT TO domain, and execute the corresponding action.  If	no  MX
	      record  is found,	look up	A or AAAA records, just	like the Post-
	      fix SMTP client would. Note: a result of "OK" is not allowed for
	      safety  reasons. Instead,	use DUNNO in order to exclude specific
	      hosts from denylists.  This feature is available in Postfix  2.1
	      and later.

       check_recipient_ns_access type:table
	      Search  the specified access(5) database for the DNS servers for
	      the RCPT TO domain, and execute the corresponding	action.	 Note:
	      a	result of "OK" is not allowed for safety reasons. Instead, use
	      DUNNO in order to	exclude	specific hosts from  denylists.	  This
	      feature is available in Postfix 2.1 and later.

       permit_auth_destination
	      Permit the request when one of the following is true:

       o      Postfix is a mail	forwarder: the resolved	RCPT TO	domain matches
	      $relay_domains or	a subdomain thereof, and the address  contains
	      no sender-specified routing (user@elsewhere@domain),

       o      Postfix  is  the	final destination: the resolved	RCPT TO	domain
	      matches  $mydestination,	$inet_interfaces,   $proxy_interfaces,
	      $virtual_alias_domains, or $virtual_mailbox_domains, and the ad-
	      dress contains no	sender-specified  routing  (user@elsewhere@do-
	      main).

       permit_mx_backup
	      Permit the request when the local	mail system is a backup	MX for
	      the RCPT TO domain, or when the domain is	an authorized destina-
	      tion (see	permit_auth_destination	for definition).

       o      Safety:  permit_mx_backup	 does  not  accept addresses that have
	      sender-specified	routing	  information	(example:   user@else-
	      where@domain).

       o      Safety:  permit_mx_backup	 can be	vulnerable to mis-use when ac-
	      cess is not restricted with permit_mx_backup_networks.

       o      Safety: as of Postfix version 2.3,  permit_mx_backup  no	longer
	      accepts  the  address when the local mail	system is a primary MX
	      for the recipient	domain.	 Exception:  permit_mx_backup  accepts
	      the  address  when  it  specifies	an authorized destination (see
	      permit_auth_destination for definition).

       o      Limitation: mail may be rejected in  case	 of  a	temporary  DNS
	      lookup problem with Postfix prior	to version 2.0.

       reject_non_fqdn_recipient
	      Reject  the  request when	the RCPT TO address specifies a	domain
	      that is not in fully-qualified domain form, as required  by  the
	      RFC.
	      The  non_fqdn_reject_code	 parameter specifies the response code
	      for rejected requests (default: 504).

       reject_rhsbl_recipient rbl_domain=d.d.d.d
	      Reject the request when the RCPT TO domain is listed with	the  A
	      record "d.d.d.d" under rbl_domain	(Postfix version 2.1 and later
	      only).  Each "d" is a number, or a pattern inside	"[]" that con-
	      tains one	or more	";"-separated numbers or number..number	ranges
	      (Postfix version 2.8 and later). If no "=d.d.d.d"	is  specified,
	      reject  the request when the RCPT	TO domain is listed with any A
	      record under rbl_domain.
	      The maps_rbl_reject_code parameter specifies the	response  code
	      for  rejected requests (default: 554); the default_rbl_reply pa-
	      rameter specifies	the default  server  reply;  and  the  rbl_re-
	      ply_maps	parameter specifies tables with	server replies indexed
	      by rbl_domain.  This feature is available	in Postfix version 2.0
	      and later.

       reject_unauth_destination
	      Reject the request unless	one of the following is	true:

       o      Postfix is a mail	forwarder: the resolved	RCPT TO	domain matches
	      $relay_domains  or  a  subdomain	thereof,   and	 contains   no
	      sender-specified routing (user@elsewhere@domain),

       o      Postfix  is  the	final destination: the resolved	RCPT TO	domain
	      matches  $mydestination,	$inet_interfaces,   $proxy_interfaces,
	      $virtual_alias_domains,  or  $virtual_mailbox_domains,  and con-
	      tains no sender-specified	routing	(user@elsewhere@domain).
	      The relay_domains_reject_code parameter specifies	 the  response
	      code for rejected	requests (default: 554).

       defer_unauth_destination
	      Reject  the  same	 requests as reject_unauth_destination,	with a
	      non-permanent error code.	 This feature is available in  Postfix
	      2.10 and later.

       reject_unknown_recipient_domain
	      Reject the request when Postfix is not final destination for the
	      recipient	domain,	and the	RCPT TO	domain has 1) no DNS MX	and no
	      DNS A record or 2) a malformed MX	record such as a record	with a
	      zero-length MX hostname (Postfix version 2.3 and later).
	      The reply	is specified with the unknown_address_reject_code  pa-
	      rameter  (default:  450),	 unknown_address_tempfail_action  (de-
	      fault: defer_if_permit), or 556 (nullmx, Postfix 3.0 and later).
	      See the respective parameter descriptions	for details.

       reject_unlisted_recipient  (with	 Postfix  version  2.0:	 check_recipi-
       ent_maps)
	      Reject the request when the RCPT TO address is not listed	in the
	      list of valid recipients for its domain class. See the smtpd_re-
	      ject_unlisted_recipient parameter	description for	details.  This
	      feature is available in Postfix 2.1 and later.

       reject_unverified_recipient
	      Reject  the request when mail to the RCPT	TO address is known to
	      bounce, or when the recipient address destination	is not	reach-
	      able.   Address  verification information	is managed by the ver-
	      ify(8) server; see the ADDRESS_VERIFICATION_README file for  de-
	      tails.
	      The unverified_recipient_reject_code parameter specifies the nu-
	      merical response code when an address is known  to  bounce  (de-
	      fault:  450,  change it to 550 when you are confident that it is
	      safe to do so).
	      The unverified_recipient_defer_code parameter specifies the  nu-
	      merical response code when an address probe failed due to	a tem-
	      porary problem (default: 450).
	      The unverified_recipient_tempfail_action parameter specifies the
	      action  after  address  probe failure due	to a temporary problem
	      (default:	defer_if_permit).
	      This feature breaks for aliased  addresses  with	"enable_origi-
	      nal_recipient = no" (Postfix <= 3.2).
	      This feature is available	in Postfix 2.1 and later.

       Other restrictions that are valid in this context:

       o      Generic  restrictions  that can be used in any SMTP command con-
	      text, described under smtpd_client_restrictions.

       o      SMTP   command	specific    restrictions    described	 under
	      smtpd_client_restrictions,      smtpd_helo_restrictions	   and
	      smtpd_sender_restrictions.

       Example:

       # The Postfix before 2.10 default mail relay policy. Later Postfix
       # versions implement this preferably with smtpd_relay_restrictions.
       smtpd_recipient_restrictions = permit_mynetworks, reject_unauth_destination

smtpd_reject_footer (default: empty)
       Optional	information that is appended after each	 Postfix  SMTP	server
       4XX or 5XX response.

       The following example uses "\c" at the start of the template (supported
       in Postfix 2.10 and later) to suppress the line break between the reply
       text  and  the  footer  text. With earlier Postfix versions, the	footer
       text always begins on a new line, and the "\c" is output	literally.

       /usr/local/etc/postfix/main.cf:
	   smtpd_reject_footer = \c. For assistance, call 800-555-0101.
	    Please provide the following information in	your problem report:
	    time ($localtime), client ($client_address)	and server
	    ($server_name).

       Server response:

	   550-5.5.1 <user@example> Recipient address rejected:	User
	   unknown. For	assistance, call 800-555-0101. Please provide the
	   following information in your problem report: time (Jan 4 15:42:00),
	   client (192.168.1.248) and server (mail1.example.com).

       Note: the above text is meant to	make it	easier	to  find  the  Postfix
       logfile	records	 for  a	 failed	 SMTP  session.	The text itself	is not
       logged to the Postfix SMTP server's maillog file.

       Be sure to keep the text	as short as possible. Long text	may  be	 trun-
       cated  before it	is logged to the remote	SMTP client's maillog file, or
       before it is returned to	the sender in a	delivery status	notification.

       The template text is not	subject	 to  Postfix  configuration  parameter
       $name  expansion.  Instead,  this  feature supports a limited number of
       $name attributes	in the footer text. These attributes are replaced with
       their current value for the SMTP	session.

       Note:  specify  $$name in footer	text that is looked up from regexp: or
       pcre:-based smtpd_reject_footer_maps, otherwise the Postfix server will
       not use the footer text and will	log a warning instead.

       client_address
	      The Client IP address that is logged in the maillog file.

       client_port
	      The client TCP port that is logged in the	maillog	file.

       localtime
	      The  server  local  time (Mmm dd hh:mm:ss) that is logged	in the
	      maillog file.

       server_name
	      The server's myhostname value.  This attribute is	made available
	      for  sites  with multiple	MTAs (perhaps behind a load-balancer),
	      where the	server name  can  help	the  server  support  team  to
	      quickly find the right log files.

       Notes:

       o      NOT SUPPORTED are	other attributes such as sender, recipient, or
	      main.cf parameters.

       o      For safety reasons,  text	 that  does  not  match	 $smtpd_expan-
	      sion_filter is censored.

       This  feature supports the two-character	sequence \n as a request for a
       line break in the footer	text. Postfix automatically inserts after each
       line  break the three-digit SMTP	reply code (and	optional enhanced sta-
       tus code) from the original Postfix reject message.

       To work around mail software that mis-handles multi-line	replies, spec-
       ify  the	 two-character sequence	\c at the start	of the template.  This
       suppresses the line break between the reply text	and  the  footer  text
       (Postfix	2.10 and later).

       This feature is available in Postfix 2.8	and later.

smtpd_reject_footer_maps (default: empty)
       Lookup  tables,	indexed	by the complete	Postfix	SMTP server 4xx	or 5xx
       response, with reject footer templates. See smtpd_reject_footer for de-
       tails.

       Specify zero or more "type:name"	lookup tables, separated by whitespace
       or comma. Tables	will be	searched in the	specified order	until a	 match
       is found.

       This feature is available in Postfix 3.4	and later.

smtpd_reject_unlisted_recipient	(default: yes)
       Request that the	Postfix	SMTP server rejects mail for unknown recipient
       addresses, even when no explicit	reject_unlisted_recipient  access  re-
       striction is specified. This prevents the Postfix queue from filling up
       with undeliverable MAILER-DAEMON	messages.

       An address is always considered "known" when it	matches	 a  virtual(5)
       alias or	a canonical(5) mapping.

       o      The recipient domain matches $mydestination, $inet_interfaces or
	      $proxy_interfaces, but the recipient is not listed in $local_re-
	      cipient_maps, and	$local_recipient_maps is not null.

       o      The  recipient domain matches $virtual_alias_domains but the re-
	      cipient is not listed in $virtual_alias_maps.

       o      The recipient domain matches  $virtual_mailbox_domains  but  the
	      recipient	 is  not  listed  in  $virtual_mailbox_maps, and $vir-
	      tual_mailbox_maps	is not null.

       o      The recipient domain matches $relay_domains but the recipient is
	      not  listed  in $relay_recipient_maps, and $relay_recipient_maps
	      is not null.

       This feature is available in Postfix 2.1	and later.

smtpd_reject_unlisted_sender (default: no)
       Request that the	Postfix	SMTP server rejects mail from  unknown	sender
       addresses, even when no explicit	reject_unlisted_sender access restric-
       tion is specified. This can slow	down an	explosion of forged mail  from
       worms or	viruses.

       An  address  is	always considered "known" when it matches a virtual(5)
       alias or	a canonical(5) mapping.

       o      The sender domain	matches	 $mydestination,  $inet_interfaces  or
	      $proxy_interfaces, but the sender	is not listed in $local_recip-
	      ient_maps, and $local_recipient_maps is not null.

       o      The sender domain	matches	$virtual_alias_domains but the	sender
	      is not listed in $virtual_alias_maps.

       o      The  sender  domain  matches  $virtual_mailbox_domains  but  the
	      sender  is  not  listed  in  $virtual_mailbox_maps,  and	 $vir-
	      tual_mailbox_maps	is not null.

       o      The  sender  domain matches $relay_domains but the sender	is not
	      listed in	$relay_recipient_maps,	and  $relay_recipient_maps  is
	      not null.

       This feature is available in Postfix 2.1	and later.

smtpd_relay_before_recipient_restrictions (default: see	postconf -d output)
       Evaluate	 smtpd_relay_restrictions before smtpd_recipient_restrictions.
       Historically, smtpd_relay_restrictions was evaluated after smtpd_recip-
       ient_restrictions, contradicting	documented behavior.

       Background:  the	smtpd_relay_restrictions feature is primarily designed
       to enforce a mail relaying policy,  while  smtpd_recipient_restrictions
       is  primarily designed to enforce spam blocking policy. Both are	evalu-
       ated while replying to the RCPT TO command, and both support  the  same
       features.

       This feature is available in Postfix 3.6	and later.

smtpd_relay_restrictions  (default:  permit_mynetworks,	 permit_sasl_authenti-
       cated, defer_unauth_destination)
       Access restrictions for mail relay control that the Postfix SMTP	server
       applies	in  the	 context  of the RCPT TO command, before smtpd_recipi-
       ent_restrictions.  See SMTPD_ACCESS_README, section "Delayed evaluation
       of  SMTP	 access	restriction lists" for a discussion of evaluation con-
       text and	time.

       With Postfix versions before 2.10, the rules for	relay  permission  and
       spam blocking were combined under smtpd_recipient_restrictions, result-
       ing in error-prone configuration.  As of	Postfix	2.10, relay permission
       rules are preferably implemented	with smtpd_relay_restrictions, so that
       a permissive spam blocking  policy  under  smtpd_recipient_restrictions
       will no longer result in	a permissive mail relay	policy.

       For  backwards  compatibility, sites that migrate from Postfix versions
       before 2.10 can set smtpd_relay_restrictions to the  empty  value,  and
       use smtpd_recipient_restrictions	exactly	as before.

       By default, the Postfix SMTP server accepts:

       o      Mail from	clients	whose IP address matches $mynetworks, or:

       o      Mail from	clients	who are	SASL authenticated, or:

       o      Mail  to	remote	destinations that match	$relay_domains,	except
	      for addresses that contain sender-specified routing  (user@else-
	      where@domain), or:

       o      Mail  to	local  destinations  that  match  $inet_interfaces  or
	      $proxy_interfaces,  $mydestination,  $virtual_alias_domains,  or
	      $virtual_mailbox_domains.

       IMPORTANT:  Either  the	smtpd_relay_restrictions  or the smtpd_recipi-
       ent_restrictions	parameter must specify at least	one of	the  following
       restrictions. Otherwise Postfix will refuse to receive mail:

	   reject, reject_unauth_destination

	   defer, defer_if_permit, defer_unauth_destination

       Specify	a list of restrictions,	separated by commas and/or whitespace.
       Continue	long lines by starting the next	 line  with  whitespace.   The
       same restrictions are available as documented under smtpd_recipient_re-
       strictions.

       This feature is available in Postix 2.10	and later.

smtpd_restriction_classes (default: empty)
       User-defined aliases for	groups of access restrictions. The aliases can
       be   specified	in   smtpd_recipient_restrictions  etc.,  and  on  the
       right-hand side of a Postfix access(5) table.

       One major application is	for implementing  per-recipient	 UCE  control.
       See the RESTRICTION_CLASS_README	document for other examples.

smtpd_sasl_application_name (default: smtpd)
       The  application	name that the Postfix SMTP server uses for SASL	server
       initialization. This controls the name of the SASL configuration	 file.
       The  default value is smtpd, corresponding to a SASL configuration file
       named smtpd.conf.

       This feature is available in Postfix 2.1	and 2.2. With Postfix  2.3  it
       was renamed to smtpd_sasl_path.

smtpd_sasl_auth_enable (default: no)
       Enable  SASL authentication in the Postfix SMTP server. By default, the
       Postfix SMTP server does	not use	authentication.

       If a remote SMTP	client is authenticated, the permit_sasl_authenticated
       access restriction can be used to permit	relay access, like this:

	   # With Postfix 2.10 and later, the mail relay policy	is
	   # preferably	specified under	smtpd_relay_restrictions.
	   smtpd_relay_restrictions =
	       permit_mynetworks, permit_sasl_authenticated, ...

       # With Postfix before 2.10, the relay policy can	be
       # specified only	under smtpd_recipient_restrictions.
       smtpd_recipient_restrictions =
	   permit_mynetworks, permit_sasl_authenticated, ...

       To  reject  all	SMTP connections from unauthenticated clients, specify
       "smtpd_delay_reject = yes" (which is the	default) and use:

	   smtpd_client_restrictions = permit_sasl_authenticated, reject

       See the SASL_README file	for SASL configuration and operation details.

smtpd_sasl_authenticated_header	(default: no)
       Report the SASL authenticated user name in the smtpd(8)	Received  mes-
       sage header.

       This feature is available in Postfix 2.3	and later.

smtpd_sasl_exceptions_networks (default: empty)
       What  remote  SMTP  clients the Postfix SMTP server will	not offer AUTH
       support to.

       Some clients (Netscape 4	at least) have a bug that causes them  to  re-
       quire  a	login and password whenever AUTH is offered, whether it's nec-
       essary or not. To work around this, specify, for	 example,  $mynetworks
       to prevent Postfix from offering	AUTH to	local clients.

       Specify	a list of network/netmask patterns, separated by commas	and/or
       whitespace. The mask specifies the number of bits in the	 network  part
       of  a  host  address. You can also specify "/file/name" or "type:table"
       patterns.  A "/file/name"  pattern  is  replaced	 by  its  contents;  a
       "type:table"  lookup  table  is	matched	 when  a table entry matches a
       lookup string (the lookup result	is ignored).  Continue long  lines  by
       starting	 the  next line	with whitespace. Specify "!pattern" to exclude
       an address or network block from	the list.  The form  "!/file/name"  is
       supported only in Postfix version 2.4 and later.

       Note:  IP  version 6 address information	must be	specified inside [] in
       the smtpd_sasl_exceptions_networks value, and in	files  specified  with
       "/file/name".   IP  version  6 addresses	contain	the ":"	character, and
       would otherwise be confused with	a "type:table" pattern.

       Example:

       smtpd_sasl_exceptions_networks =	$mynetworks

       This feature is available in Postfix 2.1	and later.

smtpd_sasl_local_domain	(default: empty)
       The name	of the Postfix SMTP server's local SASL	authentication realm.

       By default, the local authentication realm name is the null string.

       Examples:

       smtpd_sasl_local_domain = $mydomain
       smtpd_sasl_local_domain = $myhostname

smtpd_sasl_mechanism_filter (default: !external, static:rest)
       If non-empty, a filter for the SASL mechanism names  that  the  Postfix
       SMTP server will	announce in the	EHLO response. By default, the Postfix
       SMTP server will	not announce the EXTERNAL mechanism,  because  Postfix
       support for that	is not implemented.

       Specify	mechanism names, "/file/name" patterns,	or "type:table"	lookup
       tables, separated by comma or whitespace. The  right-hand  side	result
       from  "type:table"  lookups is ignored. Specify "!pattern" to exclude a
       mechanism name from the list.

       Examples:

       smtpd_sasl_mechanism_filter = !external,	!gssapi, static:rest
       smtpd_sasl_mechanism_filter = login, plain
       smtpd_sasl_mechanism_filter = $config_directory/smtpd_mechs

       This feature is available in Postfix 3.6	and later.

smtpd_sasl_path	(default: smtpd)
       Implementation-specific information that	the Postfix SMTP server	passes
       through	to  the	 SASL  plug-in	implementation	that  is selected with
       smtpd_sasl_type.	 Typically this	specifies the name of a	 configuration
       file or rendezvous point.

       This feature is available in Postfix 2.3	and later. In earlier releases
       it was called smtpd_sasl_application_name.

smtpd_sasl_response_limit (default: 12288)
       The maximum length of a SASL client's response to a  server  challenge.
       When  the  client's  "initial response" is longer than the normal limit
       for SMTP	commands, the client must omit its initial response, and  wait
       for  an	empty  server challenge; it can	then send what would have been
       its "initial response" as a response to	the  empty  server  challenge.
       RFC4954	requires  the server to	accept client responses	up to at least
       12288 octets of base64-encoded text.  The default  value	 is  therefore
       also the	minimum	value accepted for this	parameter.

       This  feature is	available in Postfix 3.4 and later. Prior versions use
       "line_length_limit", which may need to be raised	to accommodate	larger
       client  responses,  as may be needed with GSSAPI	authentication of Win-
       dows AD users who are members of	many groups.

smtpd_sasl_security_options (default: noanonymous)
       Postfix SMTP server SASL	security options; as of	Postfix	2.3  the  list
       of available features depends on	the SASL server	implementation that is
       selected	with smtpd_sasl_type.

       The following security features are defined for the cyrus  server  SASL
       implementation:

       Restrict	 what  authentication  mechanisms the Postfix SMTP server will
       offer to	the client.  The list of available  authentication  mechanisms
       is system dependent.

       Specify zero or more of the following:

       noplaintext
	      Disallow methods that use	plaintext passwords.

       noactive
	      Disallow methods subject to active (non-dictionary) attack.

       nodictionary
	      Disallow methods subject to passive (dictionary) attack.

       noanonymous
	      Disallow methods that allow anonymous authentication.

       forward_secrecy
	      Only allow methods that support forward secrecy (Dovecot only).

       mutual_auth
	      Only  allow  methods  that  provide  mutual  authentication (not
	      available	with Cyrus SASL	version	1).

       By default, the Postfix SMTP server accepts plaintext passwords but not
       anonymous logins.

       Warning:	 it appears that clients try authentication methods in the or-
       der as advertised by the	server (e.g., PLAIN ANONYMOUS CRAM-MD5)	 which
       means  that  if	you  disable  plaintext	passwords, clients will	log in
       anonymously, even when they should be able to use CRAM-MD5.  So,	if you
       disable plaintext logins, disable anonymous logins too.	Postfix	treats
       anonymous login as no authentication.

       Example:

       smtpd_sasl_security_options = noanonymous, noplaintext

smtpd_sasl_service (default: smtp)
       The service name	that is	passed to the SASL plug-in  that  is  selected
       with smtpd_sasl_type and	smtpd_sasl_path.

       This feature is available in Postfix 2.11 and later. Prior versions be-
       have as if "smtp" is specified.

smtpd_sasl_tls_security_options	(default: $smtpd_sasl_security_options)
       The SASL	authentication security	options	that the Postfix  SMTP	server
       uses for	TLS encrypted SMTP sessions.

       This feature is available in Postfix 2.2	and later.

smtpd_sasl_type	(default: cyrus)
       The  SASL  plug-in type that the	Postfix	SMTP server should use for au-
       thentication. The available types are listed  with  the	"postconf  -a"
       command.

       This feature is available in Postfix 2.3	and later.

smtpd_sender_login_maps	(default: empty)
       Optional	 lookup	 table	with  the SASL login names that	own the	sender
       (MAIL FROM) addresses.

       Specify zero or more "type:name"	lookup tables, separated by whitespace
       or  comma. Tables will be searched in the specified order until a match
       is found.  With lookups from indexed files such as DB or	DBM,  or  from
       networked  tables such as NIS, LDAP or SQL, the following search	opera-
       tions are done with a sender address of user@domain:

       1) user@domain
	      This table lookup	is always done and has the highest precedence.

       2) user
	      This table lookup	is done	only  when  the	 domain	 part  of  the
	      sender  address  matches $myorigin, $mydestination, $inet_inter-
	      faces or $proxy_interfaces.

       3) @domain
	      This table lookup	is done	last and has the lowest	precedence.

       In all cases the	result of table	lookup must be either "not found" or a
       list of SASL login names	separated by comma and/or whitespace.

smtpd_sender_restrictions (default: empty)
       Optional	 restrictions that the Postfix SMTP server applies in the con-
       text of a client	MAIL FROM command.  See	 SMTPD_ACCESS_README,  section
       "Delayed	 evaluation of SMTP access restriction lists" for a discussion
       of evaluation context and time.

       The default is to permit	everything.

       Specify a list of restrictions, separated by commas and/or  whitespace.
       Continue	 long  lines  by  starting the next line with whitespace.  Re-
       strictions are applied in the order as specified; the first restriction
       that matches wins.

       The  following restrictions are specific	to the sender address received
       with the	MAIL FROM command.

       check_sender_access type:table
	      Search the specified access(5) database for the  MAIL  FROM  ad-
	      dress,  domain,  parent  domains,	or localpart@, and execute the
	      corresponding action.

       check_sender_a_access type:table
	      Search the specified access(5) database for the IP addresses for
	      the  MAIL	 FROM  domain,	and  execute the corresponding action.
	      Note: a result of	"OK" is	not allowed for	 safety	 reasons.  In-
	      stead,  use  DUNNO  in  order  to	 exclude  specific  hosts from
	      denylists.  This feature is available in Postfix 3.0 and later.

       check_sender_mx_access type:table
	      Search the specified access(5) database for the MX hosts for the
	      MAIL  FROM  domain, and execute the corresponding	action.	 If no
	      MX record	is found, look up A or AAAA  records,  just  like  the
	      Postfix SMTP client would. Note: a result	of "OK"	is not allowed
	      for safety reasons. Instead, use DUNNO in	order to exclude  spe-
	      cific  hosts from	denylists.  This feature is available in Post-
	      fix 2.1 and later.

       check_sender_ns_access type:table
	      Search the specified access(5) database for the DNS servers  for
	      the  MAIL	 FROM  domain,	and  execute the corresponding action.
	      Note: a result of	"OK" is	not allowed for	 safety	 reasons.  In-
	      stead,  use  DUNNO  in  order  to	 exclude  specific  hosts from
	      denylists.  This feature is available in Postfix 2.1 and later.

       reject_authenticated_sender_login_mismatch
	      Enforces the reject_sender_login_mismatch	 restriction  for  au-
	      thenticated  clients  only. This feature is available in Postfix
	      version 2.1 and later.

       reject_known_sender_login_mismatch
	      Apply the	reject_sender_login_mismatch restriction only to  MAIL
	      FROM addresses that are known in $smtpd_sender_login_maps.  This
	      feature is available in Postfix version 2.11 and later.

       reject_non_fqdn_sender
	      Reject the request when the MAIL FROM address specifies a	domain
	      that  is	not  in	fully-qualified	domain form as required	by the
	      RFC.
	      The non_fqdn_reject_code parameter specifies the	response  code
	      for rejected requests (default: 504).

       reject_rhsbl_sender rbl_domain=d.d.d.d
	      Reject  the request when the MAIL	FROM domain is listed with the
	      A	record "d.d.d.d" under rbl_domain  (Postfix  version  2.1  and
	      later  only).   Each  "d"	 is a number, or a pattern inside "[]"
	      that contains one	or more	";"-separated numbers or  number..num-
	      ber  ranges (Postfix version 2.8 and later). If no "=d.d.d.d" is
	      specified, reject	the request  when  the	MAIL  FROM  domain  is
	      listed with any A	record under rbl_domain.
	      The  maps_rbl_reject_code	 parameter specifies the response code
	      for rejected requests (default:  554); the default_rbl_reply pa-
	      rameter  specifies  the  default	server	reply; and the rbl_re-
	      ply_maps parameter specifies tables with server replies  indexed
	      by  rbl_domain.	This  feature  is available in Postfix 2.0 and
	      later.

       reject_sender_login_mismatch
	      Reject the request when  $smtpd_sender_login_maps	 specifies  an
	      owner  for  the  MAIL FROM address, but the client is not	(SASL)
	      logged in	as that	MAIL FROM address owner; or when the client is
	      (SASL) logged in,	but the	client login name doesn't own the MAIL
	      FROM address according to	$smtpd_sender_login_maps.

       reject_unauthenticated_sender_login_mismatch
	      Enforces the reject_sender_login_mismatch	restriction for	 unau-
	      thenticated  clients  only. This feature is available in Postfix
	      version 2.1 and later.

       reject_unknown_sender_domain
	      Reject the request when Postfix is not the final destination for
	      the  sender  address,  and the MAIL FROM domain has 1) no	DNS MX
	      and no DNS A record, or 2) a  malformed  MX  record  such	 as  a
	      record  with  a zero-length MX hostname (Postfix version 2.3 and
	      later).
	      The reply	is specified with the unknown_address_reject_code  pa-
	      rameter  (default:  450),	 unknown_address_tempfail_action  (de-
	      fault: defer_if_permit), or 550 (nullmx, Postfix 3.0 and later).
	      See the respective parameter descriptions	for details.

       reject_unlisted_sender
	      Reject  the  request when	the MAIL FROM address is not listed in
	      the list of valid	recipients  for	 its  domain  class.  See  the
	      smtpd_reject_unlisted_sender  parameter description for details.
	      This feature is available	in Postfix 2.1 and later.

       reject_unverified_sender
	      Reject the request when mail to the MAIL FROM address  is	 known
	      to  bounce, or when the sender address destination is not	reach-
	      able.  Address verification information is managed by  the  ver-
	      ify(8)  server; see the ADDRESS_VERIFICATION_README file for de-
	      tails.
	      The unverified_sender_reject_code	parameter specifies the	numer-
	      ical  response code when an address is known to bounce (default:
	      450, change into 550 when	you are	confident that it is  safe  to
	      do so).
	      The  unverified_sender_defer_code	 specifies  the	 numerical re-
	      sponse code when an address probe	 failed	 due  to  a  temporary
	      problem (default:	450).
	      The  unverified_sender_tempfail_action  parameter	 specifies the
	      action after address probe failure due to	 a  temporary  problem
	      (default:	defer_if_permit).
	      This  feature  breaks  for aliased addresses with	"enable_origi-
	      nal_recipient = no" (Postfix <= 3.2).
	      This feature is available	in Postfix 2.1 and later.

       Other restrictions that are valid in this context:

       o      Generic restrictions that	can be used in any SMTP	 command  con-
	      text, described under smtpd_client_restrictions.

       o      SMTP    command	 specific    restrictions    described	 under
	      smtpd_client_restrictions	and smtpd_helo_restrictions.

       o      SMTP command specific restrictions described under smtpd_recipi-
	      ent_restrictions.	 When  recipient restrictions are listed under
	      smtpd_sender_restrictions, they have effect only with "smtpd_de-
	      lay_reject  = yes", so that $smtpd_sender_restrictions is	evalu-
	      ated at the time of the RCPT TO command.

       Examples:

       smtpd_sender_restrictions = reject_unknown_sender_domain
       smtpd_sender_restrictions = reject_unknown_sender_domain,
	   check_sender_access hash:$config_directory/access

smtpd_service_name (default: smtpd)
       The internal service that postscreen(8) hands off  allowed  connections
       to. In a	future version there may be different classes of SMTP service.

       This feature is available in Postfix 2.8.

smtpd_soft_error_limit (default: 10)
       The  number  of	errors a remote	SMTP client is allowed to make without
       delivering mail before the Postfix SMTP server slows down all  its  re-
       sponses.

       o      With  Postfix  version  2.1 and later, when the error count is >
	      $smtpd_soft_error_limit, the Postfix SMTP	server delays all  re-
	      sponses by $smtpd_error_sleep_time.

       o      With Postfix versions 2.0	and earlier, when the error count is >
	      $smtpd_soft_error_limit, the Postfix SMTP	server delays all  re-
	      sponses	by  the	 larger	 of  (number  of  errors)  seconds  or
	      $smtpd_error_sleep_time.

       o      With Postfix versions 2.0	and earlier, when the error  count  is
	      <=  $smtpd_soft_error_limit,  the	Postfix	SMTP server delays 4XX
	      and 5XX responses	by $smtpd_error_sleep_time.

smtpd_starttls_timeout (default: see postconf -d output)
       The time	limit for Postfix SMTP server write and	read operations	during
       TLS  startup  and  shutdown  handshake  procedures. The current default
       value is	stress-dependent. Before Postfix version 2.8, it was fixed  at
       300s.

       Specify	a  non-zero  time  value  (an  integral	value plus an optional
       one-letter suffix that specifies	the time unit).	 Time units:  s	 (sec-
       onds),  m  (minutes), h (hours),	d (days), w (weeks).  The default time
       unit is s (seconds).

       This feature is available in Postfix 2.2	and later.

smtpd_timeout (default:	normal:	300s, overload:	10s)
       When the	Postfix	SMTP server wants to send an SMTP server response, how
       long  the Postfix SMTP server will wait for an underlying network write
       operation to complete; and when the Postfix SMTP	server	Postfix	 wants
       to  receive  an	SMTP  client request, how long the Postfix SMTP	server
       will wait for an	underlying network read	operation to complete. See the
       smtpd_per_request_deadline  for	how  this  time	 limit may be enforced
       (with Postfix 2.9-3.6 see smtpd_per_record_deadline).

       Normally	the default limit is 300s, but it changes  under  overload  to
       just  10s.  With	Postfix	2.5 and	earlier, the SMTP server always	uses a
       time limit of 300s by default.

       Note: if	you set	SMTP time limits to very large values you may have  to
       update the global ipc_timeout parameter.

       Specify	a  non-zero  time  value  (an  integral	value plus an optional
       one-letter suffix that specifies	the time unit).	 Time units:  s	 (sec-
       onds),  m  (minutes), h (hours),	d (days), w (weeks).  The default time
       unit is s (seconds).

smtpd_tls_CAfile (default: empty)
       A file containing (PEM format) CA certificates of root CAs  trusted  to
       sign either remote SMTP client certificates or intermediate CA certifi-
       cates.  These are loaded	into memory before the smtpd(8)	server	enters
       the  chroot jail. If the	number of trusted roots	is large, consider us-
       ing smtpd_tls_CApath instead, but note that the latter  directory  must
       be  present in the chroot jail if the smtpd(8) server is	chrooted. This
       file may	also be	used to	augment	the server  certificate	 trust	chain,
       but it is best to include all the required certificates directly	in the
       server certificate file.

       Specify "smtpd_tls_CAfile = /path/to/system_CA_file" to	use  ONLY  the
       system-supplied default Certification Authority certificates.

       Specify	"tls_append_default_CA = no" to	prevent	Postfix	from appending
       the system-supplied default CAs and trusting third-party	certificates.

       By default (see smtpd_tls_ask_ccert), client certificates are  not  re-
       quested,	 and  smtpd_tls_CAfile should remain empty. If you do make use
       of client certificates, the distinguished names (DNs) of	the Certifica-
       tion Authorities	listed in smtpd_tls_CAfile are sent to the remote SMTP
       client in the client certificate	request	message.  MUAs	with  multiple
       client certificates may use the list of preferred Certification Author-
       ities to	select the correct client certificate.	You may	 want  to  put
       your  "preferred" CA or CAs in this file, and install other trusted CAs
       in $smtpd_tls_CApath.

       Example:

       smtpd_tls_CAfile	= $config_directory/CAcert.pem

       This feature is available in Postfix 2.2	and later.

smtpd_tls_CApath (default: empty)
       A directory containing (PEM format) CA certificates of root CAs trusted
       to  sign	either remote SMTP client certificates or intermediate CA cer-
       tificates. Do not forget	to create the necessary	"hash" links with, for
       example,	 "$OPENSSL_HOME/bin/c_rehash /usr/local/etc/postfix/certs". To
       use smtpd_tls_CApath in chroot mode, this directory (or a copy) must be
       inside the chroot jail.

       Specify	"smtpd_tls_CApath  = /path/to/system_CA_directory" to use ONLY
       the system-supplied default Certification Authority certificates.

       Specify "tls_append_default_CA =	no" to prevent Postfix from  appending
       the system-supplied default CAs and trusting third-party	certificates.

       By  default  (see smtpd_tls_ask_ccert), client certificates are not re-
       quested,	and smtpd_tls_CApath  should  remain  empty.  In  contrast  to
       smtpd_tls_CAfile,   DNs	 of  Certification  Authorities	 installed  in
       $smtpd_tls_CApath are not included in the  client  certificate  request
       message.	 MUAs  with  multiple  client certificates may use the list of
       preferred Certification Authorities to select the correct  client  cer-
       tificate.   You	may  want  to  put  your  "preferred"  CA  or  CAs  in
       $smtpd_tls_CAfile,  and	install	  the	remaining   trusted   CAs   in
       $smtpd_tls_CApath.

       Example:

       smtpd_tls_CApath	= $config_directory/certs

       This feature is available in Postfix 2.2	and later.

smtpd_tls_always_issue_session_ids (default: yes)
       Force  the Postfix SMTP server to issue a TLS session id, even when TLS
       session caching	is  turned  off	 (smtpd_tls_session_cache_database  is
       empty). This behavior is	compatible with	Postfix	< 2.3.

       With  Postfix 2.3 and later the Postfix SMTP server can disable session
       id generation when TLS session caching is turned	off. This keeps	remote
       SMTP  clients  from  caching  sessions  that almost certainly cannot be
       re-used.

       By default, the Postfix SMTP server always generates TLS	 session  ids.
       This works around a known defect	in mail	client applications such as MS
       Outlook,	and may	also prevent interoperability issues with other	MTAs.

       Example:

       smtpd_tls_always_issue_session_ids = no

       This feature is available in Postfix 2.3	and later.

smtpd_tls_ask_ccert (default: no)
       Ask a remote SMTP client	for a client certificate. This information  is
       needed  for certificate based mail relaying with, for example, the per-
       mit_tls_clientcerts feature.

       Some clients such as Netscape will either complain if no	certificate is
       available (for the list of CAs in $smtpd_tls_CAfile) or will offer mul-
       tiple client certificates to choose from. This may be annoying, so this
       option is "off" by default.

       This feature is available in Postfix 2.2	and later.

smtpd_tls_auth_only (default: no)
       When  TLS encryption is optional	in the Postfix SMTP server, do not an-
       nounce or accept	SASL authentication over unencrypted connections.

       This feature is available in Postfix 2.2	and later.

smtpd_tls_ccert_verifydepth (default: 9)
       The verification	depth for remote SMTP client certificates. A depth  of
       1 is sufficient if the issuing CA is listed in a	local CA file.

       The  default verification depth is 9 (the OpenSSL default) for compati-
       bility with earlier Postfix behavior. Prior to Postfix 2.5, the default
       value  was  5, but the limit was	not actually enforced. If you have set
       this to a lower	non-default  value,  certificates  with	 longer	 trust
       chains  may  now	fail to	verify.	Certificate chains with	1 or 2 CAs are
       common, deeper chains are more rare and any  number  between  5	and  9
       should suffice in practice. You can choose a lower number if, for exam-
       ple, you	trust certificates directly signed by an issuing  CA  but  not
       any CAs it delegates to.

       This feature is available in Postfix 2.2	and later.

smtpd_tls_cert_file (default: empty)
       File  with the Postfix SMTP server RSA certificate in PEM format.  This
       file may	also contain the Postfix SMTP server private  RSA  key.	  With
       Postfix	>= 3.4 the preferred way to configure server keys and certifi-
       cates is	via the	"smtpd_tls_chain_files"	parameter.

       Public Internet MX hosts	without	certificates signed by	a  "reputable"
       CA  must	 generate,  and	 be  prepared  to  present  to most clients, a
       self-signed or private-CA signed	certificate. The client	 will  not  be
       able  to	 authenticate the server, but unless it	is running Postfix 2.3
       or similar software, it will still insist on a server certificate.

       For servers that	are not	public Internet	 MX  hosts,  Postfix  supports
       configurations  with  no	certificates. This entails the use of just the
       anonymous TLS ciphers, which are	not supported by typical SMTP clients.
       Since  some  clients  may not fall back to plain	text after a TLS hand-
       shake failure, a	certificate-less Postfix SMTP server will be unable to
       receive	email  from some TLS-enabled clients. To avoid accidental con-
       figurations with	no certificates, Postfix enables certificate-less  op-
       eration	   only	    when    the	   administrator    explicitly	  sets
       "smtpd_tls_cert_file = none". This ensures that new Postfix SMTP	server
       configurations will not accidentally enable TLS without certificates.

       Note that server	certificates are not optional in TLS 1.3. To run with-
       out certificates	you'd have to disable the TLS 1.3 protocol by  includ-
       ing    '!TLSv1.3'    in	  "smtpd_tls_protocols"	  and	perhaps	  also
       "smtpd_tls_mandatory_protocols".	 It is simpler instead to just config-
       ure  a  certificate  chain.   Certificate-less  operation is not	recom-
       mended.

       Both RSA	and DSA	certificates  are  supported.	When  both  types  are
       present,	the cipher used	determines which certificate will be presented
       to the client.  For Netscape and	OpenSSL	clients	without	special	cipher
       choices the RSA certificate is preferred.

       To  enable  a remote SMTP client	to verify the Postfix SMTP server cer-
       tificate, the issuing CA	certificates must be  made  available  to  the
       client. You should include the required certificates in the server cer-
       tificate	file, the server certificate first,  then  the	issuing	 CA(s)
       (bottom-up order).

       Example:	the certificate	for "server.example.com" was issued by "inter-
       mediate CA" which itself	has a certificate of "root  CA".   Create  the
       server.pem   file   with	  "cat	 server_cert.pem   intermediate_CA.pem
       root_CA.pem > server.pem".

       If you also want	to verify client certificates issued by	these CAs, you
       can  add	 the CA	certificates to	the smtpd_tls_CAfile, in which case it
       is  not	necessary   to	 have	them   in   the	  smtpd_tls_cert_file,
       smtpd_tls_dcert_file (obsolete) or smtpd_tls_eccert_file.

       A certificate supplied here must	be usable as an	SSL server certificate
       and hence pass the "openssl verify -purpose sslserver ..." test.

       Example:

       smtpd_tls_cert_file = $config_directory/server.pem

       This feature is available in Postfix 2.2	and later.

smtpd_tls_chain_files (default:	empty)
       List of one or more PEM files, each holding one or  more	 private  keys
       directly	followed by a corresponding certificate	chain.	The file names
       are separated by	commas and/or whitespace.   This  parameter  obsoletes
       the  legacy algorithm-specific key and certificate file settings.  When
       this parameter is non-empty, the	legacy parameters are ignored,	and  a
       warning is logged if any	are also non-empty.

       With  the proliferation of multiple private key algorithms-which, as of
       OpenSSL 1.1.1, include DSA (obsolete), RSA, ECDSA, Ed25519 and Ed448-it
       is increasingly impractical to use separate parameters to configure the
       key and certificate chain for each algorithm.  Therefore,  Postfix  now
       supports	 storing multiple keys and corresponding certificate chains in
       a single	file or	in a set of files.

       Each key	must appear immediately	before the corresponding  certificate,
       optionally followed by additional issuer	certificates that complete the
       certificate chain for that key.	When  multiple	files  are  specified,
       they  are  equivalent  to a single file that is concatenated from those
       files in	the given order.  Thus,	while a	key must  always  precede  its
       certificate  and	issuer chain, it can be	in a separate file, so long as
       that file is listed immediately before the file that holds  the	corre-
       sponding	 certificate  chain.  Once all the files are concatenated, the
       sequence	of PEM objects must be:	key1, cert1,  [chain1],	 key2,	cert2,
       [chain2], ..., keyN, certN, [chainN].

       Storing	the private key	in the same file as the	corresponding certifi-
       cate is more reliable.  With the	key and	certificate in separate	files,
       there is	a chance that during key rollover a Postfix process might load
       a private key and certificate from separate  files  that	 don't	match.
       Various	operational errors may even result in a	persistent broken con-
       figuration in which the certificate does	not match the private key.

       The file	or files must contain at most one key of each type.   If,  for
       example,	 two or	more RSA keys and corresponding	chains are listed, de-
       pending on the version of OpenSSL either	only the last one will be used
       or  a  configuration  error may be detected.  Note that while "Ed25519"
       and "Ed448" are	considered  separate  algorithms,  the	various	 ECDSA
       curves  (typically  one of prime256v1, secp384r1	or secp521r1) are con-
       sidered as different parameters of a single "ECDSA" algorithm, so it is
       not presently possible to configure keys	for more than one ECDSA	curve.

       RSA  is	still  the  most  widely supported algorithm.  Presently (late
       2018), ECDSA support is common, but not yet universal, and Ed25519  and
       Ed448 support is	mostly absent.	Therefore, an RSA key should generally
       be configured, along with any additional	keys for the other  algorithms
       when desired.

       Example	(separate  files  for  each  key and corresponding certificate
       chain):

	   /usr/local/etc/postfix/main.cf:
	       smtpd_tls_chain_files =
		   ${config_directory}/ed25519.pem,
		   ${config_directory}/ed448.pem,
		   ${config_directory}/rsa.pem

	   /usr/local/etc/postfix/ed25519.pem:
	       -----BEGIN PRIVATE KEY-----
	       MC4CAQAwBQYDK2VwBCIEIEJfbbO4BgBQGBg9NAbIJaDBqZb4bC4cOkjtAH+Efbz3
	       -----END	PRIVATE	KEY-----
	       -----BEGIN CERTIFICATE-----
	       MIIBKzCB3qADAgECAhQaw+rflRreYuUZBp0HuNn/e5rMZDAFBgMrZXAwFDESMBAG
	       ...
	       nC0egv51YPDWxEHom4QA
	       -----END	CERTIFICATE-----

	   /usr/local/etc/postfix/ed448.pem:
	       -----BEGIN PRIVATE KEY-----
	       MEcCAQAwBQYDK2VxBDsEOQf+m0P+G0qi+NZ0RolyeiE5zdlPQR8h8y4jByBifpIe
	       LNler7nzHQJ1SLcOiXFHXlxp/84VZuh32A==
	       -----END	PRIVATE	KEY-----
	       -----BEGIN CERTIFICATE-----
	       MIIBdjCB96ADAgECAhQSv4oP972KypOZPNPF4fmsiQoRHzAFBgMrZXEwFDESMBAG
	       ...
	       pQcWsx+4J29e6YWH3Cy/CdUaexKP4RPCZDrPX7bk5C2BQ+eeYOxyThMA
	       -----END	CERTIFICATE-----

	   /usr/local/etc/postfix/rsa.pem:
	       -----BEGIN PRIVATE KEY-----
	       MIIEvQIBADANBgkqhkiG9w0BAQEFAASCBKcwggSjAgEAAoIBAQDc4QusgkahH9rL
	       ...
	       ahQkZ3+krcaJvDSMgvu0tDc=
	       -----END	PRIVATE	KEY-----
	       -----BEGIN CERTIFICATE-----
	       MIIC+DCCAeCgAwIBAgIUIUkrbk1GAemPCT8i9wKsTGDH7HswDQYJKoZIhvcNAQEL
	       ...
	       Rirz15HGVNTK8wzFd+nulPzwUo6dH2IU8KazmyRi7OGvpyrMlm15TRE2oyE=
	       -----END	CERTIFICATE-----

       Example (all keys and certificates in a single file):

	   /usr/local/etc/postfix/main.cf:
	       smtpd_tls_chain_files = ${config_directory}/chains.pem

	   /usr/local/etc/postfix/chains.pem:
	       -----BEGIN PRIVATE KEY-----
	       MC4CAQAwBQYDK2VwBCIEIEJfbbO4BgBQGBg9NAbIJaDBqZb4bC4cOkjtAH+Efbz3
	       -----END	PRIVATE	KEY-----
	       -----BEGIN CERTIFICATE-----
	       MIIBKzCB3qADAgECAhQaw+rflRreYuUZBp0HuNn/e5rMZDAFBgMrZXAwFDESMBAG
	       ...
	       nC0egv51YPDWxEHom4QA
	       -----END	CERTIFICATE-----
	       -----BEGIN PRIVATE KEY-----
	       MEcCAQAwBQYDK2VxBDsEOQf+m0P+G0qi+NZ0RolyeiE5zdlPQR8h8y4jByBifpIe
	       LNler7nzHQJ1SLcOiXFHXlxp/84VZuh32A==
	       -----END	PRIVATE	KEY-----
	       -----BEGIN CERTIFICATE-----
	       MIIBdjCB96ADAgECAhQSv4oP972KypOZPNPF4fmsiQoRHzAFBgMrZXEwFDESMBAG
	       ...
	       pQcWsx+4J29e6YWH3Cy/CdUaexKP4RPCZDrPX7bk5C2BQ+eeYOxyThMA
	       -----END	CERTIFICATE-----
	       -----BEGIN PRIVATE KEY-----
	       MIIEvQIBADANBgkqhkiG9w0BAQEFAASCBKcwggSjAgEAAoIBAQDc4QusgkahH9rL
	       ...
	       ahQkZ3+krcaJvDSMgvu0tDc=
	       -----END	PRIVATE	KEY-----
	       -----BEGIN CERTIFICATE-----
	       MIIC+DCCAeCgAwIBAgIUIUkrbk1GAemPCT8i9wKsTGDH7HswDQYJKoZIhvcNAQEL
	       ...
	       Rirz15HGVNTK8wzFd+nulPzwUo6dH2IU8KazmyRi7OGvpyrMlm15TRE2oyE=
	       -----END	CERTIFICATE-----

       This feature is available in Postfix 3.4	and later.

smtpd_tls_cipherlist (default: empty)
       Obsolete	Postfix	< 2.3 control for the Postfix SMTP server  TLS	cipher
       list.  It  is  easy  to	create interoperability	problems by choosing a
       non-default cipher list.	Do not use a non-default TLS cipherlist	for MX
       hosts on	the public Internet. Clients that begin	the TLS	handshake, but
       are unable to agree on a	common cipher, may not be  able	 to  send  any
       email  to  the  SMTP server. Using a restricted cipher list may be more
       appropriate for a dedicated MSA or an internal mailhub, where  one  can
       exert some control over the TLS software	and settings of	the connecting
       clients.

       Note: do	not use	"" quotes around the parameter value.

       This feature is available with Postfix version 2.2. It is not used with
       Postfix 2.3 and later; use smtpd_tls_mandatory_ciphers instead.

smtpd_tls_ciphers (default: medium)
       The minimum TLS cipher grade that the Postfix SMTP server will use with
       opportunistic TLS encryption.  Cipher  types  listed  in	 smtpd_tls_ex-
       clude_ciphers are excluded from the base	definition of the selected ci-
       pher grade.  The	default	value is "medium" for Postfix  releases	 after
       the middle of 2015, "export" for	older releases.

       When   TLS   is	 mandatory   the   cipher  grade  is  chosen  via  the
       smtpd_tls_mandatory_ciphers configuration parameter, see	there for syn-
       tax details.

       This  feature is	available in Postfix 2.6 and later. With earlier Post-
       fix releases only the smtpd_tls_mandatory_ciphers parameter  is	imple-
       mented, and opportunistic TLS always uses "export" or better (i.e. all)
       ciphers.

smtpd_tls_dcert_file (default: empty)
       File with the Postfix SMTP server DSA certificate in PEM	format.	  This
       file may	also contain the Postfix SMTP server private DSA key.  The DSA
       algorithm is obsolete and should	not be used.

       See the discussion under	smtpd_tls_cert_file for	more details.

       Example:

       smtpd_tls_dcert_file = $config_directory/server-dsa.pem

       This feature is available in Postfix 2.2	and later.

smtpd_tls_dh1024_param_file (default: empty)
       File with DH parameters that the	Postfix	SMTP server  should  use  with
       non-export EDH ciphers.

       With  Postfix  >= 3.7, built with OpenSSL version is 3.0.0 or later, if
       the parameter value is either empty or "auto", then  the	 DH  parameter
       selection  is delegated to the OpenSSL library, which selects appropri-
       ate parameters based on the TLS handshake.  This	choice is likely to be
       the  most  interoperable	with SMTP clients using	various	TLS libraries,
       and custom local	parameters are no longer recommended when using	 Post-
       fix >= 3.7 built	against	OpenSSL	3.0.0.

       The  best-practice choice of parameters uses a 2048-bit prime.  This is
       fine, despite the historical "1024" in the parameter name.  Do  not  be
       tempted	to  use	 much larger values, performance degrades quickly, and
       you may also cease to interoperate with some mainstream	SMTP  clients.
       As  of  Postfix 3.1, the	compiled-in default prime is 2048-bits,	and it
       is not strictly necessary, though perhaps somewhat beneficial to	gener-
       ate custom DH parameters.

       Instead	of  using  the	exact  same parameter sets as distributed with
       other TLS packages, it is more secure to	generate your own set  of  pa-
       rameters	with something like the	following commands:

	   openssl dhparam -out	/usr/local/etc/postfix/dh2048.pem 2048
	   openssl dhparam -out	/usr/local/etc/postfix/dh1024.pem 1024
	   # As	of Postfix 3.6,	export-grade 512-bit DH	parameters are no longer
	   # supported or needed.
	   openssl dhparam -out	/usr/local/etc/postfix/dh512.pem 512

       It is safe to share the same DH parameters between multiple Postfix in-
       stances.	 If you	prefer,	you can	generate separate parameters for  each
       instance.

       If you want to take maximal advantage of	ciphers	that offer forward se-
       crecy see the Getting started section of	 FORWARD_SECRECY_README.   The
       full document conveniently presents all information about Postfix "per-
       fect" forward secrecy support in	one place: what	 forward  secrecy  is,
       how to tweak settings, and what you can expect to see when Postfix uses
       ciphers with forward secrecy.

       Example:

       smtpd_tls_dh1024_param_file = $config_directory/dh2048.pem

       This feature is available in Postfix 2.2	and later.

smtpd_tls_dh512_param_file (default: empty)
       File with DH parameters that the	Postfix	SMTP server  should  use  with
       export-grade  EDH  ciphers.   The  default  SMTP	server cipher grade is
       "medium"	with Postfix releases after the	middle of 2015,	and as	a  re-
       sult export-grade cipher	suites are by default not used.

       With  Postfix  >=  3.6  export-grade  Diffie-Hellman key	exchange is no
       longer supported, and this parameter is silently	ignored.

       See also	the discussion under the smtpd_tls_dh1024_param_file  configu-
       ration parameter.

       Example:

       smtpd_tls_dh512_param_file = $config_directory/dh_512.pem

       This  feature  is available in Postfix 2.2 and later, but is ignored in
       Postfix 3.6 and later.

smtpd_tls_dkey_file (default: $smtpd_tls_dcert_file)
       File with the Postfix SMTP server DSA private key in PEM	format.	  This
       file  may be combined with the Postfix SMTP server DSA certificate file
       specified with $smtpd_tls_dcert_file. The DSA algorithm is obsolete and
       should not be used.

       The  private key	must be	accessible without a pass-phrase, i.e. it must
       not be encrypted. File permissions should grant read-only access	to the
       system superuser	account	("root"), and no access	to anyone else.

       This feature is available in Postfix 2.2	and later.

smtpd_tls_eccert_file (default:	empty)
       File  with  the	Postfix	 SMTP  server ECDSA certificate	in PEM format.
       This file may also contain the Postfix SMTP server private  ECDSA  key.
       With Postfix >= 3.4 the preferred way to	configure server keys and cer-
       tificates is via	the "smtpd_tls_chain_files" parameter.

       See the discussion under	smtpd_tls_cert_file for	more details.

       Example:

       smtpd_tls_eccert_file = $config_directory/ecdsa-scert.pem

       This feature is available in Postfix 2.6	and  later,  when  Postfix  is
       compiled	and linked with	OpenSSL	1.0.0 or later.

smtpd_tls_eckey_file (default: $smtpd_tls_eccert_file)
       File  with  the	Postfix	 SMTP  server ECDSA private key	in PEM format.
       This file may be	combined with the Postfix SMTP server  ECDSA  certifi-
       cate  file  specified with $smtpd_tls_eccert_file.  With	Postfix	>= 3.4
       the preferred way to configure server keys and certificates is via  the
       "smtpd_tls_chain_files" parameter.

       The  private key	must be	accessible without a pass-phrase, i.e. it must
       not be encrypted. File permissions should grant read-only access	to the
       system superuser	account	("root"), and no access	to anyone else.

       This  feature  is  available  in	Postfix	2.6 and	later, when Postfix is
       compiled	and linked with	OpenSSL	1.0.0 or later.

smtpd_tls_eecdh_grade (default:	see postconf -d	output)
       The Postfix SMTP	server security	 grade	for  ephemeral	elliptic-curve
       Diffie-Hellman  (EECDH) key exchange.   As of Postfix 3.6, the value of
       this parameter is always	ignored, and Postfix  behaves  as  though  the
       auto value (described below) was	chosen.

       The available choices are:

       auto   Use  the	most  preferred	 curve	that  is supported by both the
	      client and the server.  This setting  requires  Postfix  >=  3.2
	      compiled	and linked with	OpenSSL	>= 1.0.2.  This	is the default
	      setting under the	above conditions (and the  only	 setting  used
	      with Postfix >= 3.6).

       none   Don't  use  EECDH.  Ciphers  based on EECDH key exchange will be
	      disabled.	This is	the default in Postfix versions	2.6 and	2.7.

       strong Use EECDH	with approximately 128 bits of security	at  a  reason-
	      able computational cost. This is the default in Postfix versions
	      2.8-3.5.

       ultra  Use EECDH	with approximately 192 bits of	security  at  computa-
	      tional  cost  that  is  approximately  twice  as high as 128 bit
	      strength ECC.

       If you want to take maximal advantage of	ciphers	that offer forward se-
       crecy  see  the Getting started section of FORWARD_SECRECY_README.  The
       full document conveniently presents all information about Postfix "per-
       fect"  forward  secrecy	support	in one place: what forward secrecy is,
       how to tweak settings, and what you can expect to see when Postfix uses
       ciphers with forward secrecy.

       This feature is available in Postfix 2.6	and later, when	it is compiled
       and linked with OpenSSL 1.0.0 or	later on platforms where EC algorithms
       have not	been disabled by the vendor.

smtpd_tls_exclude_ciphers (default: empty)
       List  of	ciphers	or cipher types	to exclude from	the SMTP server	cipher
       list at all TLS security	levels.	Excluding valid	ciphers	can create in-
       teroperability  problems. DO NOT	exclude	ciphers	unless it is essential
       to do so. This is not an	OpenSSL	cipherlist; it is a simple list	 sepa-
       rated by	whitespace and/or commas. The elements are a single cipher, or
       one or more "+" separated cipher	properties, in which case only ciphers
       matching	all the	properties are excluded.

       Examples	(some of these will cause problems):

	   smtpd_tls_exclude_ciphers = aNULL
	   smtpd_tls_exclude_ciphers = MD5, DES
	   smtpd_tls_exclude_ciphers = DES+MD5
	   smtpd_tls_exclude_ciphers = AES256-SHA, DES-CBC3-MD5
	   smtpd_tls_exclude_ciphers = kEDH+aRSA

       The first setting disables anonymous ciphers. The next setting disables
       ciphers that use	the MD5	digest algorithm or the	(single)  DES  encryp-
       tion  algorithm.	The next setting disables ciphers that use MD5 and DES
       together.  The next setting disables the	two ciphers  "AES256-SHA"  and
       "DES-CBC3-MD5".	The  last  setting disables ciphers that use "EDH" key
       exchange	with RSA authentication.

       This feature is available in Postfix 2.3	and later.

smtpd_tls_fingerprint_digest (default: see postconf -d output)
       The message digest algorithm to construct remote	 SMTP  client-certifi-
       cate  fingerprints  or  public key fingerprints (Postfix	2.9 and	later)
       for check_ccert_access and permit_tls_clientcerts.

       The default algorithm is	sha256 with Postfix >= 3.6 and the compatibil-
       ity_level  set to 3.6 or	higher.	With Postfix <=	3.5, the default algo-
       rithm is	md5.

       The best-practice algorithm is now  sha256.  Recent  advances  in  hash
       function	cryptanalysis have led to md5 and sha1 being deprecated	in fa-
       vor of sha256.  However,	as long	as there are no	known "second  pre-im-
       age"  attacks  against the older	algorithms, their use in this context,
       though not recommended, is still	likely safe.

       While additional	digest algorithms are often available  with  OpenSSL's
       libcrypto, only those used by libssl in SSL cipher suites are available
       to Postfix.  You'll likely find	support	 for  md5,  sha1,  sha256  and
       sha512.

       To find the fingerprint of a specific certificate file, with a specific
       digest algorithm, run:

	   $ openssl x509 -noout -fingerprint -digest -in certfile.pem

       The text	to the right of	"=" sign is the	desired	fingerprint.  For  ex-
       ample:

	   $ openssl x509 -noout -fingerprint -sha256 -in cert.pem
	   SHA256 Fingerprint=D4:6A:AB:19:24:...:A6:CB:66:82:C0:8E:9B:EE:29:A8:1A

       To  extract  the	 public	key fingerprint	from an	X.509 certificate, you
       need to extract the public key from the certificate and compute the ap-
       propriate  digest  of its DER (ASN.1) encoding. With OpenSSL the	"-pub-
       key" option of the "x509" command extracts the  public  key  always  in
       "PEM"  format.  We pipe the result to another OpenSSL command that con-
       verts the key to	DER and	then to	the "dgst" command to compute the fin-
       gerprint.

       Example:

	   $ openssl x509 -in cert.pem -noout -pubkey |
	       openssl pkey -pubin -outform DER	|
	       openssl dgst -sha256 -c
	   (stdin)= 64:3f:1f:f6:e5:1e:d4:2a:56:8b:fc:09:1a:61:98:b5:bc:7c:60:58

       The Postfix SMTP	server and client log the peer (leaf) certificate fin-
       gerprint	and public key fingerprint when	 the  TLS  loglevel  is	 2  or
       higher.

       Example:	client-certificate access table, with sha256 fingerprints:

	   /usr/local/etc/postfix/main.cf:
	       smtpd_tls_fingerprint_digest = sha256
	       smtpd_client_restrictions =
		   check_ccert_access hash:$config_directory/access,
		   reject
	   /usr/local/etc/postfix/access:
	       # Action	folded to next line...
	       AF:88:7C:AD:51:95:6F:36:96:...:01:FB:2E:48:CD:AB:49:25:A2:3B
		   OK
	       85:16:78:FD:73:6E:CE:70:E0:...:5F:0D:3C:C8:6D:C4:2C:24:59:E1
		   permit_auth_destination

       This feature is available in Postfix 2.5	and later.

smtpd_tls_key_file (default: $smtpd_tls_cert_file)
       File  with the Postfix SMTP server RSA private key in PEM format.  This
       file may	be combined with the Postfix SMTP server RSA certificate  file
       specified with $smtpd_tls_cert_file.  With Postfix >= 3.4 the preferred
       way  to	configure  server   keys   and	 certificates	is   via   the
       "smtpd_tls_chain_files" parameter.

       The  private key	must be	accessible without a pass-phrase, i.e. it must
       not be encrypted. File permissions should grant read-only access	to the
       system superuser	account	("root"), and no access	to anyone else.

smtpd_tls_loglevel (default: 0)
       Enable  additional  Postfix  SMTP server	logging	of TLS activity.  Each
       logging level also includes the information that	is logged at  a	 lower
       logging level.

	      0	Disable	logging	of TLS activity.

	      1	 Log  only  a summary message on TLS handshake completion - no
	      logging of client	certificate trust-chain	verification errors if
	      client  certificate  verification	is not required.  With Postfix
	      2.8 and earlier, log the summary message,	peer certificate  sum-
	      mary  information	 and unconditionally log trust-chain verifica-
	      tion errors.

	      2	Also log levels	during TLS negotiation.

	      3	Also  log  hexadecimal	and  ASCII  dump  of  TLS  negotiation
	      process.

	      4	 Also  log hexadecimal and ASCII dump of complete transmission
	      after STARTTLS.

       Do not use "smtpd_tls_loglevel =	2" or higher except in case  of	 prob-
       lems. Use of loglevel 4 is strongly discouraged.

       This feature is available in Postfix 2.2	and later.

smtpd_tls_mandatory_ciphers (default: medium)
       The minimum TLS cipher grade that the Postfix SMTP server will use with
       mandatory TLS encryption. The default grade ("medium") is  sufficiently
       strong  that  any  benefit  from	globally restricting TLS sessions to a
       more stringent grade is likely negligible, especially  given  the  fact
       that  many  implementations  still  do  not  offer any stronger ("high"
       grade) ciphers, while those that	do, will always	use "high"  grade  ci-
       phers.  So  insisting on	"high" grade ciphers is	generally counter-pro-
       ductive.	Allowing "export" or "low" ciphers is  typically  not  a  good
       idea,  as  systems  limited  to	just  these  are  limited  to obsolete
       browsers. No known SMTP clients fail to support at least	 one  "medium"
       or "high" grade cipher.

       The following cipher grades are supported:

       export Enable "EXPORT" grade or stronger	OpenSSL	ciphers.  The underly-
	      ing cipherlist is	specified via the  tls_export_cipherlist  con-
	      figuration  parameter,  which you	are strongly encouraged	not to
	      change.  This choice is insecure and SHOULD NOT be used.

       low    Enable "LOW" grade or stronger OpenSSL ciphers.  The  underlying
	      cipherlist is specified via the tls_low_cipherlist configuration
	      parameter, which you are	strongly  encouraged  not  to  change.
	      This choice is insecure and SHOULD NOT be	used.

       medium Enable  "MEDIUM"	grade  or  stronger OpenSSL ciphers. These use
	      128-bit or longer	symmetric bulk-encryption keys.	 This  is  the
	      default  minimum	strength for mandatory TLS encryption. The un-
	      derlying cipherlist is specified via  the	 tls_medium_cipherlist
	      configuration  parameter,	 which you are strongly	encouraged not
	      to change.

       high   Enable only "HIGH" grade OpenSSL	ciphers.  The  underlying  ci-
	      pherlist	is specified via the tls_high_cipherlist configuration
	      parameter, which you are strongly	encouraged to not change.

       null   Enable only the "NULL" OpenSSL ciphers, these provide  authenti-
	      cation  without encryption.  This	setting	is only	appropriate in
	      the rare case that all clients are prepared to use NULL  ciphers
	      (not normally enabled in TLS clients). The underlying cipherlist
	      is specified via the tls_null_cipherlist	configuration  parame-
	      ter, which you are strongly encouraged not to change.

       Cipher	types	listed	 in   smtpd_tls_mandatory_exclude_ciphers   or
       smtpd_tls_exclude_ciphers are excluded from the base definition of  the
       selected	 cipher	 grade.	See smtpd_tls_ciphers for cipher controls that
       apply to	opportunistic TLS.

       The underlying cipherlists for grades other than	"null" include	anony-
       mous ciphers, but these are automatically filtered out if the server is
       configured to ask for remote SMTP client	certificates.	You  are  very
       unlikely	 to  need to take any steps to exclude anonymous ciphers, they
       are excluded automatically as required.	If you must exclude  anonymous
       ciphers	even  when Postfix does	not need or use	peer certificates, set
       "smtpd_tls_exclude_ciphers = aNULL". To exclude anonymous ciphers  only
       when  TLS  is  enforced,	set "smtpd_tls_mandatory_exclude_ciphers = aN-
       ULL".

       This feature is available in Postfix 2.3	and later.

smtpd_tls_mandatory_exclude_ciphers (default: empty)
       Additional list of ciphers or cipher types to exclude from the  Postfix
       SMTP  server  cipher  list at mandatory TLS security levels.  This list
       works in	addition to the	exclusions listed  with	 smtpd_tls_exclude_ci-
       phers (see there	for syntax details).

       This feature is available in Postfix 2.3	and later.

smtpd_tls_mandatory_protocols (default:	see postconf -d	output)
       TLS  protocols  accepted	 by the	Postfix	SMTP server with mandatory TLS
       encryption.  If the list	is empty, the server  supports	all  available
       TLS  protocol  versions.	 A non-empty value is a	list of	protocol names
       to include or exclude, separated	by whitespace, commas or colons.

       The valid protocol names	(see SSL_get_version(3)) are "SSLv2", "SSLv3",
       "TLSv1",	 "TLSv1.1",  "TLSv1.2"	and  "TLSv1.3".	 Starting with Postfix
       3.6, the	default	value is ">=TLSv1", which sets TLS 1.0 as  the	lowest
       supported TLS protocol version (see below).  Older releases use the "!"
       exclusion syntax, also described	below.

       As of Postfix 3.6, the preferred	way to limit the range	of  acceptable
       protocols  is  to set the lowest	acceptable TLS protocol	version	and/or
       the highest acceptable TLS protocol version.  To	set  the  lower	 bound
       include	an  element of the form: ">=version" where version is a	either
       one of the TLS protocol names listed above,  or	a  hexadecimal	number
       corresponding  to  the  desired TLS protocol version (0301 for TLS 1.0,
       0302 for	TLS 1.1, etc.).	 For the upper bound, use "<=version".	 There
       must be no whitespace between the ">=" or "<=" symbols and the protocol
       name or number.

       Hexadecimal protocol numbers  make  it  possible	 to  specify  protocol
       bounds  for  TLS	 versions  that	are known to OpenSSL, but might	not be
       known to	Postfix.  They cannot be used with the legacy  exclusion  syn-
       tax.   Leading  "0"  or	"0x" prefixes are supported, but not required.
       Therefore, "301", "0301", "0x301" and "0x0301" are  all	equivalent  to
       "TLSv1".	  Hexadecimal versions unknown to OpenSSL will fail to set the
       upper or	lower bound, and a warning will	be logged.   Hexadecimal  ver-
       sions  should only be used when Postfix is linked with some future ver-
       sion of OpenSSL that supports TLS 1.4 or	later, but  Postfix  does  not
       yet support a symbolic name for that protocol version.

       Hexadecimal example (Postfix >= 3.6):

	   # Allow only	TLS 1.2	through	(hypothetical) TLS 1.4,	once supported
	   # in	some future version of OpenSSL (presently a warning is logged).
	   smtpd_tls_mandatory_protocols = >=TLSv1.2, <=0305
	   # Allow only	TLS 1.2	and up:
	   smtpd_tls_mandatory_protocols = >=0x0303

       With  Postfix  <	 3.6 there is no support for a minimum or maximum ver-
       sion, and the protocol range is configured via protocol exclusions.  To
       require	at least TLS 1.0, set "smtpd_tls_mandatory_protocols = !SSLv2,
       !SSLv3".	 Listing the protocols to include, rather  than	 protocols  to
       exclude,	 is  supported,	 but not recommended.  The exclusion form more
       accurately matches the underlying OpenSSL interface.

       Support for "TLSv1.3" was introduced in OpenSSL 1.1.1.  Disabling  this
       protocol	 via  "!TLSv1.3"  is supported since Postfix 3.4 (or patch re-
       leases >= 3.0.14, 3.1.10, 3.2.7 and 3.3.2).

       Example:

       # Preferred syntax with Postfix >= 3.6:
       smtpd_tls_mandatory_protocols = >=TLSv1.2, <=TLSv1.3
       # Legacy	syntax:
       smtpd_tls_mandatory_protocols = !SSLv2, !SSLv3, !TLSv1, !TLSv1.1

       This feature is available in Postfix 2.3	and later.

smtpd_tls_protocols (default: see postconf -d output)
       TLS protocols accepted by the Postfix SMTP  server  with	 opportunistic
       TLS encryption. If the list is empty, the server	supports all available
       TLS protocol versions.  A non-empty value is a list of  protocol	 names
       to include or exclude, separated	by whitespace, commas or colons.

       The valid protocol names	(see SSL_get_version(3)) are "SSLv2", "SSLv3",
       "TLSv1",	"TLSv1.1", "TLSv1.2" and  "TLSv1.3".   Starting	 with  Postfix
       3.6,  the  default value	is ">=TLSv1", which sets TLS 1.0 as the	lowest
       supported TLS protocol version (see below).  Older releases use the "!"
       exclusion syntax, also described	below.

       As  of  Postfix 3.6, the	preferred way to limit the range of acceptable
       protocols is to set the lowest acceptable TLS protocol  version	and/or
       the  highest  acceptable	 TLS protocol version.	To set the lower bound
       include an element of the form: ">=version" where version is  a	either
       one  of	the  TLS  protocol names listed	above, or a hexadecimal	number
       corresponding to	the desired TLS	protocol version (0301	for  TLS  1.0,
       0302  for TLS 1.1, etc.).  For the upper	bound, use "<=version".	 There
       must be no whitespace between the ">=" or "<=" symbols and the protocol
       name or number.

       Hexadecimal  protocol  numbers  make  it	 possible  to specify protocol
       bounds for TLS versions that are	known to OpenSSL,  but	might  not  be
       known  to  Postfix.  They cannot	be used	with the legacy	exclusion syn-
       tax.  Leading "0" or "0x" prefixes are  supported,  but	not  required.
       Therefore,  "301",  "0301",  "0x301" and	"0x0301" are all equivalent to
       "TLSv1".	 Hexadecimal versions unknown to OpenSSL will fail to set  the
       upper  or  lower	bound, and a warning will be logged.  Hexadecimal ver-
       sions should only be used when Postfix is linked	with some future  ver-
       sion  of	 OpenSSL  that supports	TLS 1.4	or later, but Postfix does not
       yet support a symbolic name for that protocol version.

       Hexadecimal example (Postfix >= 3.6):

	   # Allow only	TLS 1.0	through	(hypothetical) TLS 1.4,	once supported
	   # in	some future version of OpenSSL (presently a warning is logged).
	   smtpd_tls_protocols = >=TLSv1, <=0305
	   # Allow only	TLS 1.0	and up:
	   smtpd_tls_protocols = >=0x0301

       With Postfix < 3.6 there	is no support for a minimum  or	 maximum  ver-
       sion, and the protocol range is configured via protocol exclusions.  To
       require at least	TLS 1.0, set "smtpd_tls_protocols =  !SSLv2,  !SSLv3".
       Listing	the protocols to include, rather than protocols	to exclude, is
       supported, but not recommended.	The  exclusion	form  more  accurately
       matches the underlying OpenSSL interface.

       Support	for "TLSv1.3" was introduced in	OpenSSL	1.1.1.	Disabling this
       protocol	via "!TLSv1.3" is supported since Postfix 3.4  (or  patch  re-
       leases >= 3.0.14, 3.1.10, 3.2.7 and 3.3.2).

       Example:
       # Preferred syntax with Postfix >= 3.6:
       smtpd_tls_protocols = >=TLSv1, <=TLSv1.3
       # Legacy	syntax:
       smtpd_tls_protocols = !SSLv2, !SSLv3

       This feature is available in Postfix 2.6	and later.

smtpd_tls_received_header (default: no)
       Request	that the Postfix SMTP server produces Received:	 message head-
       ers that	include	information about the protocol	and  cipher  used,  as
       well as the remote SMTP client CommonName and client certificate	issuer
       CommonName.  This is disabled by	default, as  the  information  may  be
       modified	 in transit through other mail servers.	 Only information that
       was recorded by the final destination can be trusted.

       This feature is available in Postfix 2.2	and later.

smtpd_tls_req_ccert (default: no)
       With mandatory TLS encryption, require a	 trusted  remote  SMTP	client
       certificate  in order to	allow TLS connections to proceed.  This	option
       implies "smtpd_tls_ask_ccert = yes".

       When TLS	encryption is optional,	this setting is	ignored	with a warning
       written to the mail log.

       This feature is available in Postfix 2.2	and later.

smtpd_tls_security_level (default: empty)
       The  SMTP  TLS  security	 level	for  the  Postfix  SMTP	server;	when a
       non-empty value is specified, this overrides  the  obsolete  parameters
       smtpd_use_tls  and  smtpd_enforce_tls.  This  parameter is ignored with
       "smtpd_tls_wrappermode =	yes".

       Specify one of the following security levels:

       none   TLS will not be used.

       may    Opportunistic TLS: announce  STARTTLS  support  to  remote  SMTP
	      clients, but do not require that clients use TLS encryption.

       encrypt
	      Mandatory	 TLS  encryption:  announce STARTTLS support to	remote
	      SMTP clients, and	require	that clients use TLS  encryption.  Ac-
	      cording  to  RFC 2487 this MUST NOT be applied in	case of	a pub-
	      licly-referenced SMTP server. Instead,  this  option  should  be
	      used only	on dedicated servers.

       Note  1:	 the  "fingerprint", "verify" and "secure" levels are not sup-
       ported here.  The Postfix SMTP server logs a warning and	uses "encrypt"
       instead.	 To verify remote SMTP client certificates, see	TLS_README for
       a discussion of the smtpd_tls_ask_ccert,	smtpd_tls_req_ccert, and  per-
       mit_tls_clientcerts features.

       Note  2:	The parameter setting "smtpd_tls_security_level	= encrypt" im-
       plies "smtpd_tls_auth_only = yes".

       Note 3: when invoked via	 "sendmail  -bs",  Postfix  will  never	 offer
       STARTTLS	 due  to  insufficient privileges to access the	server private
       key. This is intended behavior.

       This feature is available in Postfix 2.3	and later.

smtpd_tls_session_cache_database (default: empty)
       Name of the file	containing the optional	Postfix	SMTP server  TLS  ses-
       sion  cache. Specify a database type that supports enumeration, such as
       btree or	sdbm; there is no need to support concurrent access.  The file
       is  created if it does not exist. The smtpd(8) daemon does not use this
       parameter directly, rather the cache is implemented indirectly  in  the
       tlsmgr(8)  daemon.  This	 means that per-smtpd-instance master.cf over-
       rides of	this parameter are not effective. Note that each of the	 cache
       databases supported by tlsmgr(8)	daemon:	$smtpd_tls_session_cache_data-
       base, $smtp_tls_session_cache_database (and with	Postfix	2.3 and	 later
       $lmtp_tls_session_cache_database), needs	to be stored separately. It is
       not at this time	possible to store multiple caches in  a	 single	 data-
       base.

       Note:  dbm  databases  are  not	suitable.  TLS session objects are too
       large.

       As of version 2.5, Postfix no longer uses root privileges when  opening
       this  file.  The	 file  should  now  be	stored under the Postfix-owned
       data_directory. As a migration aid, an attempt to open the file under a
       non-Postfix  directory  is  redirected to the Postfix-owned data_direc-
       tory, and a warning is logged.

       As of Postfix 2.11 the preferred	mechanism for  session	resumption  is
       RFC  5077 TLS session tickets, which don't require server-side storage.
       Consequently, for Postfix >= 2.11 this parameter	 should	 generally  be
       left  empty.   TLS session tickets require an OpenSSL library (at least
       version 0.9.8h) that provides full support for this TLS extension.  See
       also smtpd_tls_session_cache_timeout.

       Example:

       smtpd_tls_session_cache_database	= btree:/var/lib/postfix/smtpd_scache

       This feature is available in Postfix 2.2	and later.

smtpd_tls_session_cache_timeout	(default: 3600s)
       The  expiration	time of	Postfix	SMTP server TLS	session	cache informa-
       tion. A cache cleanup is	performed periodically	every  $smtpd_tls_ses-
       sion_cache_timeout  seconds. As with $smtpd_tls_session_cache_database,
       this parameter is implemented in	the  tlsmgr(8)	daemon	and  therefore
       per-smtpd-instance master.cf overrides are not possible.

       As  of  Postfix 2.11 this setting cannot	exceed 100 days.  If set <= 0,
       session caching is disabled, not	just via the database,	but  also  via
       RFC  5077 TLS session tickets, which don't require server-side storage.
       If set to a positive value less than 2 minutes, the minimum value of  2
       minutes	is  used  instead.  TLS	session	tickets	require	an OpenSSL li-
       brary (at least version 0.9.8h) that provides full support for this TLS
       extension.

       Specify	a  non-negative	time value (an integral	value plus an optional
       one-letter suffix that specifies	the time unit).	 Time units:  s	 (sec-
       onds),  m  (minutes), h (hours),	d (days), w (weeks).  The default time
       unit is s (seconds).

       This feature is available in Postfix 2.2	and later, and updated for TLS
       session ticket support in Postfix 2.11.

smtpd_tls_wrappermode (default:	no)
       Run the Postfix SMTP server in TLS "wrapper" mode, instead of using the
       STARTTLS	command.

       If you want to support this service, enable  a  special	port  in  mas-
       ter.cf, and specify "-o smtpd_tls_wrappermode=yes" on the SMTP server's
       command line. Port 465 (submissions/smtps) is reserved  for  this  pur-
       pose.

       This feature is available in Postfix 2.2	and later.

smtpd_upstream_proxy_protocol (default:	empty)
       The  name  of the proxy protocol	used by	an optional before-smtpd proxy
       agent. When a proxy agent is used, this protocol	conveys	local and  re-
       mote  address and port information.  Specify "smtpd_upstream_proxy_pro-
       tocol = haproxy"	to enable the haproxy protocol;	version	2 is supported
       with Postfix 3.5	and later.

       NOTE: To	use the	nginx proxy with smtpd(8), enable the XCLIENT protocol
       with smtpd_authorized_xclient_hosts. This supports SASL	authentication
       in the proxy agent (Postfix 2.9 and later).

       This feature is available in Postfix 2.10 and later.

smtpd_upstream_proxy_timeout (default: 5s)
       The  time  limit	 for  the  proxy protocol specified with the smtpd_up-
       stream_proxy_protocol parameter.

       Specify a non-zero time value  (an  integral  value  plus  an  optional
       one-letter  suffix  that	specifies the time unit).  Time	units: s (sec-
       onds), m	(minutes), h (hours), d	(days),	w (weeks).  The	 default  time
       unit is s (seconds).

       This feature is available in Postfix 2.10 and later.

smtpd_use_tls (default:	no)
       Opportunistic  TLS:  announce  STARTTLS support to remote SMTP clients,
       but do not require that clients use TLS encryption.

       Note: when invoked via "sendmail	-bs", Postfix will never offer	START-
       TLS  due	 to  insufficient privileges to	access the server private key.
       This is intended	behavior.

       This feature is available in Postfix 2.2	and later.  With  Postfix  2.3
       and later use smtpd_tls_security_level instead.

smtputf8_autodetect_classes (default: sendmail,	verify)
       Detect  that a message requires SMTPUTF8	support	for the	specified mail
       origin classes.	This is	a workaround to	avoid chicken-and-egg problems
       during  the initial SMTPUTF8 roll-out in	environments with pre-existing
       mail flows that contain UTF8. Those mail	flows should not break because
       Postfix	suddenly refuses to deliver such mail to down-stream MTAs that
       don't announce SMTPUTF8 support.

       The problem is that Postfix cannot rely solely on the sender's declara-
       tion  that a message requires SMTPUTF8 support, because UTF8 may	be in-
       troduced	during local processing	(for example, the client  hostname  in
       Postfix's  Received:  header, adding @$myorigin or .$mydomain to	an in-
       complete	address, address rewriting, alias expansion, automatic BCC re-
       cipients, local forwarding, and changes made by header checks or	Milter
       applications).

       For now,	the default is to  enable  "SMTPUTF8  required"	 autodetection
       only  for Postfix sendmail command-line submissions and address verifi-
       cation probes.  This may	change once SMTPUTF8  support  achieves	 world
       domination.   However, sites that add UTF8 content via local processing
       (see above) should autodetect the need for  SMTPUTF8  support  for  all
       email.

       Specify one or more of the following:

	sendmail
	      Submission with the Postfix sendmail(1) command.

	smtpd Mail received with the smtpd(8) daemon.

	qmqpd Mail received with the qmqpd(8) daemon.

	forward
	      Local  forwarding	 or aliasing.  When a message is received with
	      "SMTPUTF8	required", then	the forwarded (aliased)	message	always
	      has "SMTPUTF8 required".

	bounce
	      Submission  by the bounce(8) daemon.  When a message is received
	      with "SMTPUTF8 required",	then the delivery status  notification
	      always has "SMTPUTF8 required".

	notify
	      Postmaster notification from the smtp(8) or smtpd(8) daemon.

	verify
	      Address verification probe from the verify(8) daemon.

	all   Enable SMTPUTF8 autodetection for	all mail.

       This feature is available in Postfix 3.0	and later.

smtputf8_enable	(default: yes)
       Enable  preliminary SMTPUTF8 support for	the protocols described	in RFC
       6531, RFC 6532, and RFC 6533. This requires that	Postfix	 is  built  to
       support these protocols.

       This feature is available in Postfix 3.0	and later.

soft_bounce (default: no)
       Safety  net to keep mail	queued that would otherwise be returned	to the
       sender.	This parameter disables	locally-generated bounces, changes the
       handling	 of negative responses from remote servers, content filters or
       plugins,	and prevents the Postfix SMTP server from rejecting mail  per-
       manently	by changing 5xx	reply codes into 4xx.  However,	soft_bounce is
       no cure for address rewriting mistakes or mail routing mistakes.

       Note: "soft_bounce = yes" is in some  cases  implemented	 by  modifying
       server  responses. Therefore, the response that Postfix logs may	differ
       from the	response that Postfix actually sends or	receives.

       Example:

       soft_bounce = yes

stale_lock_time	(default: 500s)
       The time	after which a stale exclusive  mailbox	lockfile  is  removed.
       This is used for	delivery to file or mailbox.

       Specify	a  non-zero  time  value  (an  integral	value plus an optional
       one-letter suffix that specifies	the time unit).	 Time units:  s	 (sec-
       onds),  m  (minutes), h (hours),	d (days), w (weeks).  The default time
       unit is s (seconds).

stress (default: empty)
       This feature is documented in the STRESS_README document.

       This feature is available in Postfix 2.5	and later.

strict_7bit_headers (default: no)
       Reject mail with	8-bit text in message headers. This blocks  mail  from
       poorly written applications.

       This  feature  should  not be enabled on	a general purpose mail server,
       because it is likely to reject legitimate email.

       This feature is available in Postfix 2.0	and later.

strict_8bitmime	(default: no)
       Enable both strict_7bit_headers and strict_8bitmime_body.

       This feature should not be enabled on a general	purpose	 mail  server,
       because it is likely to reject legitimate email.

       This feature is available in Postfix 2.0	and later.

strict_8bitmime_body (default: no)
       Reject  8-bit message body text without 8-bit MIME content encoding in-
       formation.  This	blocks mail from poorly	written	applications.

       Unfortunately, this also	rejects	majordomo approval requests  when  the
       included	request	contains valid 8-bit MIME mail,	and it rejects bounces
       from mailers that do not	MIME encapsulate 8-bit content	(for  example,
       bounces from qmail or from old versions of Postfix).

       This  feature  should  not be enabled on	a general purpose mail server,
       because it is likely to reject legitimate email.

       This feature is available in Postfix 2.0	and later.

strict_mailbox_ownership (default: yes)
       Defer delivery when a mailbox file is not owned by its recipient.   The
       default setting is not backwards	compatible.

       This feature is available in Postfix 2.5.3 and later.

strict_mime_encoding_domain (default: no)
       Reject mail with	invalid	Content-Transfer-Encoding: information for the
       message/* or multipart/*	MIME content types.   This  blocks  mail  from
       poorly written software.

       This  feature  should  not be enabled on	a general purpose mail server,
       because it will reject mail after a single violation.

       This feature is available in Postfix 2.0	and later.

strict_rfc821_envelopes	(default: no)
       Require that addresses received in SMTP MAIL FROM and RCPT TO  commands
       are  enclosed  with <>, and that	those addresses	do not contain RFC 822
       style comments or phrases.  This	stops mail from	poorly	written	 soft-
       ware.

       By default, the Postfix SMTP server accepts RFC 822 syntax in MAIL FROM
       and RCPT	TO addresses.

strict_smtputf8	(default: no)
       Enable stricter enforcement of the SMTPUTF8 protocol. The Postfix  SMTP
       server  accepts UTF8 sender or recipient	addresses only when the	client
       requests	an SMTPUTF8 mail transaction.

       This feature is available in Postfix 3.0	and later.

sun_mailtool_compatibility (default: no)
       Obsolete	SUN mailtool compatibility feature. Instead, use  "mailbox_de-
       livery_lock = dotlock".

swap_bangpath (default:	yes)
       Enable  the  rewriting of "site!user" into "user@site".	This is	neces-
       sary if your machine is connected to UUCP networks.  It is  enabled  by
       default.

       Note:  with  Postfix version 2.2, message header	address	rewriting hap-
       pens only when one of the following conditions is true:

       o      The message is received with the Postfix sendmail(1) command,

       o      The message is received from a network client that matches  $lo-
	      cal_header_rewrite_clients,

       o      The   message   is  received  from  the  network,	 and  the  re-
	      mote_header_rewrite_domain  parameter  specifies	 a   non-empty
	      value.

       To   get	  the  behavior	 before	 Postfix  version  2.2,	 specify  "lo-
       cal_header_rewrite_clients = static:all".

       Example:

       swap_bangpath = no

syslog_facility	(default: mail)
       The syslog facility of Postfix logging. Specify a facility  as  defined
       in syslog.conf(5). The default facility is "mail".

       Warning:	 a non-default syslog_facility setting takes effect only after
       a Postfix process has completed initialization.	Errors during  process
       initialization  will be logged with the default facility.  Examples are
       errors while parsing the	command	line arguments,	and errors  while  ac-
       cessing the Postfix main.cf configuration file.

syslog_name (default: see postconf -d output)
       A  prefix  that	is prepended to	the process name in syslog records, so
       that, for example, "smtpd" becomes "prefix/smtpd".

       Warning:	a non-default syslog_name setting takes	effect	only  after  a
       Postfix	process	 has  completed	 initialization. Errors	during process
       initialization will be logged with the default name. Examples  are  er-
       rors while parsing the command line arguments, and errors while access-
       ing the Postfix main.cf configuration file.

tcp_windowsize (default: 0)
       An optional workaround for  routers  that  break	 TCP  window  scaling.
       Specify	a  value > 0 and < 65536 to enable this	feature.  With Postfix
       TCP servers (smtpd(8), qmqpd(8)), this feature is  implemented  by  the
       Postfix master(8) daemon.

       To  change  this	 parameter without stopping Postfix, you need to first
       terminate all Postfix TCP servers:

	   # postconf -e master_service_disable=inet
	   # postfix reload

       This immediately	terminates all processes that accept  network  connec-
       tions.	Next, you enable Postfix TCP servers with the updated tcp_win-
       dowsize setting:

	   # postconf -e tcp_windowsize=65535 master_service_disable=
	   # postfix reload

       If you skip these  steps	 with  a  running  Postfix  system,  then  the
       tcp_windowsize  change will work	only for Postfix TCP clients (smtp(8),
       lmtp(8)).

       This feature is available in Postfix 2.6	and later.

tls_append_default_CA (default:	no)
       Append the system-supplied default Certification	Authority certificates
       to  the	ones specified with *_tls_CApath or *_tls_CAfile.  The default
       is "no";	this prevents Postfix from trusting  third-party  certificates
       and giving them relay permission	with permit_tls_all_clientcerts.

       This  feature  is available in Postfix 2.4.15, 2.5.11, 2.6.8, 2.7.2 and
       later versions. Specify "tls_append_default_CA  =  yes"	for  backwards
       compatibility,  to  avoid  breaking certificate verification with sites
       that don't use permit_tls_all_clientcerts.

tls_daemon_random_bytes	(default: 32)
       The number of pseudo-random bytes that an smtp(8) or  smtpd(8)  process
       requests	from the tlsmgr(8) server in order to seed its internal	pseudo
       random number generator (PRNG).	The default of 32 bytes	(equivalent to
       256 bits) is sufficient to generate a 128bit (or	168bit)	session	key.

       This feature is available in Postfix 2.2	and later.

tls_dane_digest_agility	(default: on)
       Configure  RFC7671  DANE	 TLSA digest algorithm agility.	 Do not	change
       this setting from its default value.

       See Section 8 of	RFC7671	for correct key	rotation procedures.

       This feature is available in Postfix 2.11 through 3.1.  Postfix 3.2 and
       later  ignore this configuration	parameter and behave as	though it were
       set to "on".

tls_dane_digests (default: sha512 sha256)
       DANE TLSA (RFC 6698, RFC	 7671,	RFC  7672)  resource-record  "matching
       type" digest algorithms in descending preference	order.	All the	speci-
       fied algorithms must be supported by the	 underlying  OpenSSL  library,
       otherwise the Postfix SMTP client will not support DANE TLSA security.

       Specify	a  list	of digest names	separated by commas and/or whitespace.
       Each digest name	may be followed	by  an	optional  "=<number>"  suffix.
       For  example,  "sha512"	may  instead  be  specified  as	"sha512=2" and
       "sha256"	may instead be specified as "sha256=1".	 The  optional	number
       must  match  the	<a href="https://www.iana.org/assignments/dane-parame-
       ters/dane-parameters.xhtml#matching-types" >IANA	assigned TLSA matching
       type  number  the  algorithm in question.  Postfix will check this con-
       straint for the algorithms it knows about.   Additional	matching  type
       algorithms registered with IANA can be added with explicit numbers pro-
       vided they are supported	by OpenSSL.

       Invalid list elements are logged	with a warning and disable  DANE  sup-
       port.   TLSA  RRs that specify digests not included in the list are ig-
       nored with a warning.

       Note: It	is unwise to omit sha256 from the digest  list.	  This	digest
       algorithm  is  the  only	mandatory to implement digest algorithm	in RFC
       6698, and many servers are expected to publish TLSA records  with  just
       sha256  digests.	  Unless one of	the standard digests is	seriously com-
       promised	and servers have had ample time	to update their	 TLSA  records
       you  should  not	 omit any standard digests, just arrange them in order
       from strongest to weakest.

       This feature is available in Postfix 2.11 and later.

tls_dane_trust_anchor_digest_enable (default: yes)
       Enable support for RFC 6698 (DANE TLSA) DNS records  that  contain  di-
       gests  of trust-anchors with certificate	usage "2".  Do not change this
       setting from its	default	value.

       This feature is available in Postfix 2.11 through  3.1.	 It  has  been
       withdrawn  in  Postfix 3.2, as trust-anchor TLSA	records	are now	widely
       used and	have proved sufficiently reliable.  Postfix 3.2	and later  ig-
       nore  this configuration	parameter and behaves as though	it were	set to
       "yes".

tls_disable_workarounds	(default: see postconf -d output)
       List or bit-mask	of OpenSSL bug work-arounds to disable.

       The OpenSSL toolkit includes a set of work-arounds  for	buggy  SSL/TLS
       implementations.	 Applications,	such as	Postfix, that want to maximize
       interoperability	ask the	OpenSSL	library	to enable the full set of rec-
       ommended	work-arounds.

       From  time to time, it is discovered that a work-around creates a secu-
       rity issue, and should no longer	be used. If  upgrading	OpenSSL	 to  a
       fixed  version  is  not	an  option or an upgrade is not	available in a
       timely manner, or in closed environments	 where	no  buggy  clients  or
       servers	exist,	it  may	 be  appropriate to disable some or all	of the
       OpenSSL interoperability	work-arounds. This parameter  specifies	 which
       bug work-arounds	to disable.

       If  the	value  of the parameter	is a hexadecimal long integer starting
       with "0x", the bug work-arounds corresponding to	the bits specified  in
       its  value  are	removed	 from the SSL_OP_ALL work-around bit-mask (see
       openssl/ssl.h and SSL_CTX_set_options(3)). You can  specify  more  bits
       than  are  present  in  SSL_OP_ALL, excess bits are ignored. Specifying
       0xFFFFFFFF disables all bug-workarounds on a 32-bit system. This	should
       also  be	 sufficient  on	64-bit systems,	until OpenSSL abandons support
       for 32-bit systems and starts using  the	 high  32  bits	 of  a	64-bit
       bug-workaround mask.

       Otherwise,  the	parameter  is a	white-space or comma separated list of
       specific	named bug work-arounds chosen from the list below. It is  pos-
       sible that your OpenSSL version includes	new bug	work-arounds added af-
       ter your	Postfix	source code was	last updated, in  that	case  you  can
       only disable one	of these via the hexadecimal syntax above.

       CRYPTOPRO_TLSEXT_BUG
	      New with GOST support in OpenSSL 1.0.0.

       DONT_INSERT_EMPTY_FRAGMENTS
	      See SSL_CTX_set_options(3)

       LEGACY_SERVER_CONNECT
	      See SSL_CTX_set_options(3)

       MICROSOFT_BIG_SSLV3_BUFFER
	      See SSL_CTX_set_options(3)

       MICROSOFT_SESS_ID_BUG
	      See SSL_CTX_set_options(3)

       MSIE_SSLV2_RSA_PADDING
	      also   aliased  as  CVE-2005-2969.  Postfix  2.8	disables  this
	      work-around by default with OpenSSL versions  that  may  predate
	      the fix. Fixed in	OpenSSL	0.9.7h and OpenSSL 0.9.8a.

       NETSCAPE_CHALLENGE_BUG
	      See SSL_CTX_set_options(3)

       NETSCAPE_REUSE_CIPHER_CHANGE_BUG
	      also   aliased  as  CVE-2010-4180.  Postfix  2.8	disables  this
	      work-around by default with OpenSSL versions  that  may  predate
	      the fix. Fixed in	OpenSSL	0.9.8q and OpenSSL 1.0.0c.

       SSLEAY_080_CLIENT_DH_BUG
	      See SSL_CTX_set_options(3)

       SSLREF2_REUSE_CERT_TYPE_BUG
	      See SSL_CTX_set_options(3)

       TLS_BLOCK_PADDING_BUG
	      See SSL_CTX_set_options(3)

       TLS_D5_BUG
	      See SSL_CTX_set_options(3)

       TLS_ROLLBACK_BUG
	      See  SSL_CTX_set_options(3).   This is disabled in OpenSSL 0.9.7
	      and later. Nobody	should still be	using 0.9.6!

       TLSEXT_PADDING
	      Postfix >= 3.4. See SSL_CTX_set_options(3).

       This feature is available in Postfix 2.8	and later.

tls_eecdh_auto_curves (default:	see postconf -d	output)
       The prioritized list of elliptic	curves supported by the	 Postfix  SMTP
       client  and  server.   These curves are used by the Postfix SMTP	server
       when "smtpd_tls_eecdh_grade = auto".  The selected curves must  be  im-
       plemented by OpenSSL and	be standardized	for use	in TLS (RFC 8422).  It
       is unwise to list only "bleeding-edge" curves supported by a small sub-
       set of clients.	The default list is suitable for most users.

       Postfix	skips  curve  names  that  are unknown to OpenSSL, or that are
       known but not yet implemented.  This makes it possible to  "anticipate"
       support	for curves that	should be used once they become	available.  In
       particular, in some OpenSSL versions, the new RFC 8031 curves  "X25519"
       and  "X448"  may	 be known by name, but ECDH support for	either or both
       may be missing.	These curves may appear	in the default value  of  this
       parameter,  even	 though	 they'll only be usable	with later versions of
       OpenSSL.

       This feature is available in Postfix 3.2	and later, when	it is compiled
       and linked with OpenSSL 1.0.2 or	later on platforms where EC algorithms
       have not	been disabled by the vendor.

tls_eecdh_strong_curve (default: prime256v1)
       The elliptic curve used by the Postfix SMTP server for sensibly	strong
       ephemeral  ECDH	key  exchange.	This curve is used by the Postfix SMTP
       server when "smtpd_tls_eecdh_grade  =  strong".	The  phrase  "sensibly
       strong"	means  approximately  128-bit security based on	best known at-
       tacks. The selected curve must be implemented by	OpenSSL	 (as  reported
       by  ecparam(1) with the "-list_curves" option) and be one of the	curves
       listed in Section 5.1.1 of RFC 8422. You	should	not  generally	change
       this  setting.	Remote	SMTP  client implementations must support this
       curve for EECDH key exchange to take place.  It	is  unwise  to	choose
       only  "bleeding-edge"  curves  supported	 by  only  a  small  subset of
       clients.

       The default "strong" curve is rated in  NSA  Suite  B  for  information
       classified up to	SECRET.

       Note: elliptic curve names are poorly standardized; different standards
       groups are assigning different names to	the  same  underlying  curves.
       The curve with the X9.62	name "prime256v1" is also known	under the SECG
       name "secp256r1", but OpenSSL does not recognize	the latter name.

       If you want to take maximal advantage of	ciphers	that offer forward se-
       crecy  see  the Getting started section of FORWARD_SECRECY_README.  The
       full document conveniently presents all information about Postfix "per-
       fect"  forward  secrecy	support	in one place: what forward secrecy is,
       how to tweak settings, and what you can expect to see when Postfix uses
       ciphers with forward secrecy.

       This feature is available in Postfix 2.6	and later, when	it is compiled
       and linked with OpenSSL 1.0.0 or	later on platforms where EC algorithms
       have not	been disabled by the vendor.

tls_eecdh_ultra_curve (default:	secp384r1)
       The elliptic curve used by the Postfix SMTP server for maximally	strong
       ephemeral ECDH key exchange. This curve is used	by  the	 Postfix  SMTP
       server  when  "smtpd_tls_eecdh_grade  =	ultra".	 The phrase "maximally
       strong" means approximately 192-bit security based on  best  known  at-
       tacks.	This  additional strength comes	at a significant computational
       cost, most users	should instead set "smtpd_tls_eecdh_grade  =  strong".
       The  selected  curve must be implemented	by OpenSSL (as reported	by ec-
       param(1)	with the "-list_curves"	option)	 and  be  one  of  the	curves
       listed  in  Section  5.1.1 of RFC 8422. You should not generally	change
       this setting.  Remote SMTP client  implementations  must	 support  this
       curve  for  EECDH  key  exchange	to take	place.	It is unwise to	choose
       only "bleeding-edge"  curves  supported	by  only  a  small  subset  of
       clients.

       This  default  "ultra"  curve  is  rated	in NSA Suite B for information
       classified up to	TOP SECRET.

       If you want to take maximal advantage of	ciphers	that offer forward se-
       crecy  see  the Getting started section of FORWARD_SECRECY_README.  The
       full document conveniently presents all information about Postfix "per-
       fect"  forward  secrecy	support	in one place: what forward secrecy is,
       how to tweak settings, and what you can expect to see when Postfix uses
       ciphers with forward secrecy.

       This feature is available in Postfix 2.6	and later, when	it is compiled
       and linked with OpenSSL 1.0.0 or	later on platforms where EC algorithms
       have not	been disabled by the vendor.

tls_export_cipherlist (default:	see postconf -d	output)
       The  OpenSSL  cipherlist	for "export" or	higher grade ciphers. This de-
       fines  the  meaning  of	the  "export"  setting	in  smtpd_tls_ciphers,
       smtpd_tls_mandatory_ciphers,  smtp_tls_ciphers,	smtp_tls_mandatory_ci-
       phers, lmtp_tls_ciphers,	and lmtp_tls_mandatory_ciphers.	 With  Postfix
       releases	 before	 the middle of 2015 this is the	default	cipherlist for
       the opportunistic ("may") TLS client security level and	also  the  de-
       fault  cipherlist  for the SMTP server. You are strongly	encouraged not
       to change this setting.

       This feature is available in Postfix 2.3	and later.

tls_fast_shutdown_enable (default: yes)
       A workaround for	implementations	that hang Postfix while	shutting  down
       a TLS session, until Postfix times out. With this enabled, Postfix will
       not wait	for the	remote TLS peer	to respond to a	TLS 'close'  notifica-
       tion. This behavior is recommended for TLSv1.0 and later.

tls_high_cipherlist (default: see postconf -d output)
       The OpenSSL cipherlist for "high" grade ciphers.	This defines the mean-
       ing of the "high" setting in smtpd_tls_ciphers, smtpd_tls_mandatory_ci-
       phers,  smtp_tls_ciphers, smtp_tls_mandatory_ciphers, lmtp_tls_ciphers,
       and lmtp_tls_mandatory_ciphers. You  are	 strongly  encouraged  not  to
       change this setting.

       This feature is available in Postfix 2.3	and later.

tls_legacy_public_key_fingerprints (default: no)
       A  temporary  migration	aid  for sites that use	certificate public-key
       fingerprints with Postfix 2.9.0..2.9.5, which use  an  incorrect	 algo-
       rithm. This parameter has no effect on the certificate fingerprint sup-
       port that is available since Postfix 2.2.

       Specify "tls_legacy_public_key_fingerprints = yes" temporarily, pending
       a   migration   from   configuration   files   with  incorrect  Postfix
       2.9.0..2.9.5 certificate	public-key finger prints, to the correct  fin-
       gerprints used by Postfix 2.9.6 and later.  To compute the correct cer-
       tificate	public-key fingerprints, see TLS_README.

       This feature is available in Postfix 2.9.6 and later.

tls_low_cipherlist (default: see postconf -d output)
       The OpenSSL cipherlist for "low"	or higher grade	ciphers. This  defines
       the meaning of the "low"	setting	in smtpd_tls_ciphers, smtpd_tls_manda-
       tory_ciphers,	   smtp_tls_ciphers,	   smtp_tls_mandatory_ciphers,
       lmtp_tls_ciphers,  and lmtp_tls_mandatory_ciphers. You are strongly en-
       couraged	not to change this setting.

       This feature is available in Postfix 2.3	and later.

tls_medium_cipherlist (default:	see postconf -d	output)
       The OpenSSL cipherlist for "medium" or higher grade ciphers.  This  de-
       fines  the  meaning  of	the  "medium"  setting	in  smtpd_tls_ciphers,
       smtpd_tls_mandatory_ciphers,  smtp_tls_ciphers,	smtp_tls_mandatory_ci-
       phers,  lmtp_tls_ciphers,  and lmtp_tls_mandatory_ciphers.  This	is the
       default cipherlist for mandatory	TLS encryption in the TLS client (with
       anonymous  ciphers  disabled when verifying server certificates).  This
       is the default cipherlist for opportunistic TLS with  Postfix  releases
       after  the  middle  of 2015.  You are strongly encouraged not to	change
       this setting.

       This feature is available in Postfix 2.3	and later.

tls_null_cipherlist (default: eNULL:!aNULL)
       The OpenSSL cipherlist for "NULL" grade ciphers that provide  authenti-
       cation  without encryption. This	defines	the meaning of the "null" set-
       ting  in	 smtpd_tls_mandatory_ciphers,  smtp_tls_mandatory_ciphers  and
       lmtp_tls_mandatory_ciphers.   You are strongly encouraged not to	change
       this setting.

       This feature is available in Postfix 2.3	and later.

tls_preempt_cipherlist (default: no)
       With SSLv3 and later, use the Postfix SMTP server's  cipher  preference
       order instead of	the remote client's cipher preference order.

       By  default, the	OpenSSL	server selects the client's most preferred ci-
       pher that the server supports. With SSLv3 and  later,  the  server  may
       choose its own most preferred cipher that is supported (offered)	by the
       client. Setting "tls_preempt_cipherlist = yes"  enables	server	cipher
       preferences.

       While  server  cipher selection may in some cases lead to a more	secure
       or performant cipher choice, there is some risk of interoperability is-
       sues.  In the past, some	SSL clients have listed	lower priority ciphers
       that they did not implement correctly. If the server chooses  a	cipher
       that  the  client prefers less, it may select a cipher whose client im-
       plementation is flawed. Most notably Windows  2003  Microsoft  Exchange
       servers have flawed implementations of DES-CBC3-SHA, which OpenSSL con-
       siders stronger than RC4-SHA.  Enabling server  cipher-suite  selection
       may create interoperability issues with Windows 2003 Microsoft Exchange
       clients.

       This feature is available in Postfix 2.8	and later, in combination with
       OpenSSL 0.9.7 and later.

tls_random_bytes (default: 32)
       The  number  of bytes that tlsmgr(8) reads from $tls_random_source when
       (re)seeding the in-memory pseudo	random number generator	 (PRNG)	 pool.
       The  default of 32 bytes	(256 bits) is good enough for 128bit symmetric
       keys.  If using EGD or a	device file, a maximum of 255 bytes is read.

       This feature is available in Postfix 2.2	and later.

tls_random_exchange_name (default: see postconf	-d output)
       Name of the pseudo random number	generator (PRNG) state	file  that  is
       maintained  by  tlsmgr(8).  The file is created when it does not	exist,
       and its length is fixed at 1024 bytes.

       As of version 2.5, Postfix no longer uses root privileges when  opening
       this  file, and the default file	location was changed from ${config_di-
       rectory}/prng_exch to ${data_directory}/prng_exch.  As a	migration aid,
       an attempt to open the file under a non-Postfix directory is redirected
       to the Postfix-owned data_directory, and	a warning is logged.

       This feature is available in Postfix 2.2	and later.

tls_random_prng_update_period (default:	3600s)
       The time	between	attempts by tlsmgr(8) to save the state	of the	pseudo
       random  number  generator  (PRNG)  to the file specified	with $tls_ran-
       dom_exchange_name.

       Specify a non-zero time value  (an  integral  value  plus  an  optional
       one-letter  suffix  that	specifies the time unit).  Time	units: s (sec-
       onds), m	(minutes), h (hours), d	(days),	w (weeks).  The	 default  time
       unit is s (seconds).

       This feature is available in Postfix 2.2	and later.

tls_random_reseed_period (default: 3600s)
       The maximal time	between	attempts by tlsmgr(8) to re-seed the in-memory
       pseudo random number generator (PRNG) pool from external	sources.   The
       actual  time  between re-seeding	attempts is calculated using the PRNG,
       and is between 0	and the	time specified.

       Specify a non-zero time value  (an  integral  value  plus  an  optional
       one-letter  suffix  that	specifies the time unit).  Time	units: s (sec-
       onds), m	(minutes), h (hours), d	(days),	w (weeks).  The	 default  time
       unit is s (seconds).

       This feature is available in Postfix 2.2	and later.

tls_random_source (default: see	postconf -d output)
       The  external  entropy source for the in-memory tlsmgr(8) pseudo	random
       number generator	(PRNG) pool. Be	sure to	specify	a non-blocking source.
       If  this	 source	is not a regular file, the entropy source type must be
       prepended:  egd:/path/to/egd_socket for a source	 with  EGD  compatible
       socket interface, or dev:/path/to/device	for a device file.

       Note: on	OpenBSD	systems	specify	dev:/dev/arandom when dev:/dev/urandom
       gives timeout errors.

       This feature is available in Postfix 2.2	and later.

tls_server_sni_maps (default: empty)
       Optional	lookup tables that map names received from remote SMTP clients
       via  the	 TLS Server Name Indication (SNI) extension to the appropriate
       keys and	certificate chains.  This  parameter  is  implemented  in  the
       Postfix	TLS  library, and applies to both smtpd(8) and the SMTP	server
       mode of tlsproxy(8).

       When this parameter is non-empty, the Postfix SMTP server  enables  SNI
       extension  processing,  and  logs  SNI values that are invalid or don't
       match an	entry in the specified tables.	When an	entry does match,  the
       SNI  name  is  logged as	part of	the connection summary at log levels 1
       and higher.

       The lookup key is either	the verbatim SNI domain	name  or  an  ancestor
       domain prefixed with a leading dot.  For	internationalized domains, the
       lookup key must be in IDNA 2008 A-label form (as	required  in  the  TLS
       SNI extension).

       The   syntax   of   the	 lookup	  value	  is  the  same	 as  with  the
       smtp_tls_chain_files parameter (see there for additional	details),  but
       here  scoped to just TLS	connections in which the client	sends a	match-
       ing SNI domain name.

       Example:

	   /usr/local/etc/postfix/main.cf:
	       #
	       # The indexed SNI table must be created with "postmap -F"
	       #
	       indexed = ${default_database_type}:${config_directory}/
	       tls_server_sni_maps = ${indexed}sni

	   /usr/local/etc/postfix/sni:
	       #
	       # The example.com domain	has both an RSA	and ECDSA certificate
	       # chain.	 The chain files MUST start with the private key,
	       # with the certificate chain next, starting with	the leaf
	       # (server) certificate, and then	the issuer certificates.
	       #
	       example.com /usr/local/etc/postfix/sni-chains/rsa2048.example.com.pem,
			   /usr/local/etc/postfix/sni-chains/ecdsa-p256.example.com.pem
	       #
	       # The example.net domain	has a wildcard certificate, and	two
	       # additional DNS	names.	So its certificate chain is also used
	       # with any subdomain, plus the additional names.
	       #
	       example.net /usr/local/etc/postfix/sni-chains/example.net.pem
	       .example.net /usr/local/etc/postfix/sni-chains/example.net.pem
	       example.info /usr/local/etc/postfix/sni-chains/example.net.pem
	       example.org /usr/local/etc/postfix/sni-chains/example.net.pem

       Note that the SNI lookup	tables should also have	entries	 for  the  do-
       mains  that  correspond	to  the	Postfix	SMTP server's default certifi-
       cate(s).	This ensures that the remote SMTP client's TLS	SNI  extension
       gets  a	positive  response  when  it specifies one of the Postfix SMTP
       server's	default	domains, and ensures that the Postfix SMTP server will
       not  log	 an  SNI  name	mismatch  for such a domain.  The Postfix SMTP
       server's	default	certificates are then only used	when the client	 sends
       no SNI or when it sends SNI with	a domain that the server knows no cer-
       tificate(s) for.

       The mapping from	an SNI domain name to a	certificate chain is indirect.
       In  the	input  source files for	"cdb", "hash", "btree" or other	tables
       that are	converted to on-disk indexed files via postmap(1),  the	 value
       specified for each key is a list	of filenames.  When postmap(1) is used
       with the	-F option, the generated table stores for each lookup key  the
       base64-encoded  contents	of the associated files.  When querying	tables
       via postmap -Fq,	the table value	is decoded from	base64,	 yielding  the
       original	file content, plus a new line.

       With  "regexp",	"pcre",	"inline", "texthash", "static" and similar ta-
       bles that are interpreted at run-time, and don't	have a separate	source
       format,	the  table  value  is again a list files, that are loaded into
       memory when the table is	opened.

       With tables whose content is managed outside of Postfix,	such as	 LDAP,
       MySQL, PostgreSQL, socketmap and	tcp, the value must be a concatenation
       of the desired PEM keys and certificate chains, that  is	 then  further
       encoded	to yield a single-line base64 string.  Creation	of such	tables
       and secure storage (the value includes private key material)  are  out-
       side the	responsibility of Postfix.

       With  "socketmap"  and "tcp" the	data will be transmitted in the	clear,
       and there is no query access control, so	these are generally unsuitable
       for  storing  SNI  chains.  With	LDAP and SQL, you should restrict read
       access and use TLS to protect the sensitive data	in transit.

       Typically there is only one private key and its chain  of  certificates
       starting	 with  the  "leaf"  certificate	corresponding to that key, and
       continuing with the appropriate intermediate  issuer  CA	 certificates,
       with  each  certificate	ideally	 followed by its issuer.  Servers that
       have keys and certificates for more than	one algorithm (e.g.   both  an
       RSA  key	and an ECDSA key, or even RSA, ECDSA and Ed25519) can use mul-
       tiple chains concatenated together, with	the key	always	listed	before
       the corresponding certificates.

       This feature is available in Postfix 3.4	and later.

tls_session_ticket_cipher  (default:  Postfix  >=  3.0:	aes-256-cbc, Postfix <
       3.0: aes-128-cbc)
       Algorithm used to encrypt RFC5077 TLS session tickets.  This  algorithm
       must  use  CBC  mode,  have  a  128-bit block size, and must have a key
       length between 128 and 256 bits.	 The default is	aes-256-cbc.  Overrid-
       ing the default to choose a different algorithm is discouraged.

       Setting	this  parameter	 empty	disables session ticket	support	in the
       Postfix SMTP server.  Another way to disable session ticket support  is
       via the tls_ssl_options parameter.

       This feature is available in Postfix 3.0	and later.

tls_ssl_options	(default: empty)
       List or bit-mask	of OpenSSL options to enable.

       The OpenSSL toolkit provides a set of options that applications can en-
       able to tune the	OpenSSL	behavior.  Some	of these work around  bugs  in
       other  implementations and are on by default.  You can use the tls_dis-
       able_workarounds	parameter to selectively disable some or  all  of  the
       bug  work-arounds, making OpenSSL more strict at	the cost of non-inter-
       operability with	SSL clients or servers that exhibit the	bugs.

       Other options are off by	default, and typically enable or disable  fea-
       tures rather than bug work-arounds.  These may be turned	on (with care)
       via the tls_ssl_options parameter.  The value is	a white-space or comma
       separated  list of named	options	chosen from the	list below.  The names
       are not case-sensitive, you can use lower-case if you prefer.  The  up-
       per  case  values below match the corresponding macro name in the ssl.h
       header file with	the SSL_OP_ prefix removed.  It	is possible that  your
       OpenSSL	version	 includes  new options added after your	Postfix	source
       code was	last updated, in that case you can only	enable	one  of	 these
       via the hexadecimal syntax below.

       You  should only	enable features	via the	hexadecimal mask when the need
       to control the feature is critical (to deal with	a new vulnerability or
       a  serious  interoperability  problem).	Postfix	DOES NOT promise back-
       wards compatible	behavior with respect to the mask bits.	 A feature en-
       abled  via  the	mask in	one release may	be enabled by other means in a
       later release, and the mask bit will then be ignored.   Therefore,  use
       of the hexadecimal mask is only a temporary measure until a new Postfix
       or OpenSSL release provides a better solution.

       If the value of the parameter is	a hexadecimal  long  integer  starting
       with "0x", the options corresponding to the bits	specified in its value
       are enabled (see	openssl/ssl.h and  SSL_CTX_set_options(3)).   You  can
       only  enable  options not already controlled by other Postfix settings.
       For example, you	cannot disable protocols or enable server cipher pref-
       erence.	  Do   not  attempt  to	 enable	 all  features	by  specifying
       0xFFFFFFFF, this	is unlikely to be a good idea.	Some bug  work-arounds
       are  also valid here, allowing them to be re-enabled if/when they're no
       longer enabled by default.  The supported values	include:

       ENABLE_MIDDLEBOX_COMPAT
	      Postfix >= 3.4. See SSL_CTX_set_options(3).

       LEGACY_SERVER_CONNECT
	      See SSL_CTX_set_options(3).

       NO_TICKET
	      Enabled by default when needed in	fully-patched Postfix >=  2.7.
	      Not  needed  at  all for Postfix >= 2.11,	unless for some	reason
	      you do not want to support TLS session resumption.  Best not set
	      explicitly.  See SSL_CTX_set_options(3).

       NO_COMPRESSION
	      Disable  SSL  compression	 even  if supported by the OpenSSL li-
	      brary.  Compression is CPU-intensive, and	compression before en-
	      cryption does not	always improve security.

       NO_RENEGOTIATION
	      Postfix  >=  3.4.	 This can reduce opportunities for a potential
	      CPU exhaustion attack.  See SSL_CTX_set_options(3).

       NO_SESSION_RESUMPTION_ON_RENEGOTIATION
	      Postfix >= 3.4. See SSL_CTX_set_options(3).

       PRIORITIZE_CHACHA
	      Postfix >= 3.4. See SSL_CTX_set_options(3).

       This feature is available in Postfix 2.11 and later.

tls_wildcard_matches_multiple_labels (default: yes)
       Match multiple DNS labels with "*" in wildcard certificates.

       Some mail service providers prepend the customer	domain name to a  base
       domain  for  which  they	have a wildcard	TLS certificate.  For example,
       the MX records for example.com hosted by	example.net may	be:

	   example.com.	IN MX 0	example.com.mx1.example.net.
	   example.com.	IN MX 0	example.com.mx2.example.net.

       and the TLS certificate may be for "*.example.net". The "*" then	corre-
       sponds  with  multiple  labels  in  the mail server domain name.	 While
       multi-label wildcards are not widely supported, and are not blessed  by
       any  standard, there is little to be gained by disallowing their	use in
       this context.

       Notes:

       o      In a certificate name, the "*" is	special	only when it  is  used
	      as the first label.

       o      While Postfix (2.11 or later) can	match "*" with multiple	domain
	      name labels, other implementations likely	will not.

       o      Earlier  Postfix	implementations	 behave	  as   if   "tls_wild-
	      card_matches_multiple_labels = no".

       This feature is available in Postfix 2.11 and later.

tlsmgr_service_name (default: tlsmgr)
       The  name  of  the  tlsmgr(8)  service entry in master.cf. This service
       maintains TLS session caches and	other information in support of	TLS.

       This feature is available in Postfix 2.11 and later.

tlsproxy_client_CAfile (default: $smtp_tls_CAfile)
       A file containing CA certificates of root CAs trusted  to  sign	either
       remote  TLS  server  certificates or intermediate CA certificates.  See
       smtp_tls_CAfile for further details.

       This feature is available in Postfix 3.4	and later.

tlsproxy_client_CApath (default: $smtp_tls_CApath)
       Directory with PEM format Certification Authority certificates that the
       Postfix	tlsproxy(8) client uses	to verify a remote TLS server certifi-
       cate. See smtp_tls_CApath for further details.

       This feature is available in Postfix 3.4	and later.

tlsproxy_client_cert_file (default: $smtp_tls_cert_file)
       File with the Postfix tlsproxy(8) client	RSA certificate	in PEM format.
       See  smtp_tls_cert_file for further details.  The preferred way to con-
       figure  tlsproxy	 client	 keys  and  certificates  is  via   the	  "tl-
       sproxy_client_chain_files" parameter.

       This feature is available in Postfix 3.4	and later.

tlsproxy_client_chain_files (default: $smtp_tls_chain_files)
       Files  with  the	Postfix	tlsproxy(8) client keys	and certificate	chains
       in PEM format. See smtp_tls_chain_files for further details.

       This feature is available in Postfix 3.4	and later.

tlsproxy_client_dcert_file (default: $smtp_tls_dcert_file)
       File with the Postfix tlsproxy(8) client	DSA certificate	in PEM format.
       See smtp_tls_dcert_file for further details. DSA	is obsolete and	should
       not be used.

       This feature is available in Postfix 3.4	and later.

tlsproxy_client_dkey_file (default: $smtp_tls_dkey_file)
       File with the Postfix tlsproxy(8) client	DSA private key	in PEM format.
       See  smtp_tls_dkey_file for further details. DSA	is obsolete and	should
       not be used.

       This feature is available in Postfix 3.4	and later.

tlsproxy_client_eccert_file (default: $smtp_tls_eccert_file)
       File with the Postfix tlsproxy(8) client	ECDSA certificate in PEM  for-
       mat. See	smtp_tls_eccert_file for further details. The preferred	way to
       configure tlsproxy  client  keys	 and  certificates  is	via  the  "tl-
       sproxy_client_chain_files" parameter.

       This feature is available in Postfix 3.4	and later.

tlsproxy_client_eckey_file (default: $smtp_tls_eckey_file)
       File  with the Postfix tlsproxy(8) client ECDSA private key in PEM for-
       mat. See	smtp_tls_eckey_file for	further	details.  The preferred	way to
       configure  tlsproxy  client  keys  and  certificates  is	 via  the "tl-
       sproxy_client_chain_files" parameter.

       This feature is available in Postfix 3.4	and later.

tlsproxy_client_enforce_tls (default: $smtp_enforce_tls)
       Enforcement mode: require that SMTP servers use	TLS  encryption.   See
       smtp_enforce_tls	  for	further	  details.  Use	 tlsproxy_client_secu-
       rity_level instead.

       This feature is available in Postfix 3.4	and later.

tlsproxy_client_fingerprint_digest (default: $smtp_tls_fingerprint_digest)
       The message digest algorithm used to construct remote TLS  server  cer-
       tificate	 fingerprints. See smtp_tls_fingerprint_digest for further de-
       tails.

       This feature is available in Postfix 3.4	and later.

tlsproxy_client_key_file (default: $smtp_tls_key_file)
       File with the Postfix tlsproxy(8) client	RSA private key	in PEM format.
       See smtp_tls_key_file for further details. The preferred	way to config-
       ure  tlsproxy  client  keys  and	  certificates	 is   via   the	  "tl-
       sproxy_client_chain_files" parameter.

       This feature is available in Postfix 3.4	and later.

tlsproxy_client_level (default:	$smtp_tls_security_level)
       The  default TLS	security level for the Postfix tlsproxy(8) client. See
       smtp_tls_security_level for further details.

       This feature is available in Postfix 3.4	- 3.6. It was renamed  to  tl-
       sproxy_client_security_level in Postfix 3.7.

tlsproxy_client_loglevel (default: $smtp_tls_loglevel)
       Enable  additional  Postfix tlsproxy(8) client logging of TLS activity.
       See smtp_tls_loglevel for further details.

       This feature is available in Postfix 3.4	and later.

tlsproxy_client_loglevel_parameter (default: smtp_tls_loglevel)
       The name	of the parameter that  provides	 the  tlsproxy_client_loglevel
       value.

       This feature is available in Postfix 3.4	and later.

tlsproxy_client_per_site (default: $smtp_tls_per_site)
       Optional	 lookup	 tables	 with the Postfix tlsproxy(8) client TLS usage
       policy by next-hop destination and by remote TLS	server hostname.   See
       smtp_tls_per_site for further details.

       This feature is available in Postfix 3.4	and later.

tlsproxy_client_policy (default: $smtp_tls_policy_maps)
       Optional	lookup tables with the Postfix tlsproxy(8) client TLS security
       policy by next-hop destination. See  smtp_tls_policy_maps  for  further
       details.

       This  feature  is available in Postfix 3.4 - 3.6. It was	renamed	to tl-
       sproxy_client_policy_maps in Postfix 3.7.

tlsproxy_client_policy_maps (default: $smtp_tls_policy_maps)
       Optional	lookup tables with the Postfix tlsproxy(8) client TLS security
       policy  by  next-hop  destination. See smtp_tls_policy_maps for further
       details.

       This feature is available in Postfix 3.7	and later. It  was  previously
       called tlsproxy_client_policy.

tlsproxy_client_scert_verifydepth (default: $smtp_tls_scert_verifydepth)
       The  verification  depth	 for  remote  TLS  server  certificates.   See
       smtp_tls_scert_verifydepth for further details.

       This feature is available in Postfix 3.4	and later.

tlsproxy_client_security_level (default: $smtp_tls_security_level)
       The default TLS security	level for the Postfix tlsproxy(8) client.  See
       smtp_tls_security_level for further details.

       This  feature  is available in Postfix 3.7 and later. It	was previously
       called tlsproxy_client_level.

tlsproxy_client_use_tls	(default: $smtp_use_tls)
       Opportunistic mode: use TLS when	a remote server	announces TLS support.
       See   smtp_use_tls   for	 further  details.  Use	 tlsproxy_client_secu-
       rity_level instead.

       This feature is available in Postfix 3.4	and later.

tlsproxy_enforce_tls (default: $smtpd_enforce_tls)
       Mandatory TLS: announce STARTTLS	support	to remote  SMTP	 clients,  and
       require that clients use	TLS encryption.	See smtpd_enforce_tls for fur-
       ther details. Use tlsproxy_tls_security_level instead.

       This feature is available in Postfix 2.8	and later.

tlsproxy_service_name (default:	tlsproxy)
       The name	of the tlsproxy(8) service entry in  master.cf.	 This  service
       performs	plaintext <=> TLS ciphertext conversion.

       This feature is available in Postfix 2.8	and later.

tlsproxy_tls_CAfile (default: $smtpd_tls_CAfile)
       A  file	containing (PEM	format)	CA certificates	of root	CAs trusted to
       sign either remote SMTP client certificates or intermediate CA certifi-
       cates.  See smtpd_tls_CAfile for	further	details.

       This feature is available in Postfix 2.8	and later.

tlsproxy_tls_CApath (default: $smtpd_tls_CApath)
       A directory containing (PEM format) CA certificates of root CAs trusted
       to sign either remote SMTP client certificates or intermediate CA  cer-
       tificates. See smtpd_tls_CApath for further details.

       This feature is available in Postfix 2.8	and later.

tlsproxy_tls_always_issue_session_ids  (default:  $smtpd_tls_always_issue_ses-
       sion_ids)
       Force the Postfix tlsproxy(8) server to issue a TLS  session  id,  even
       when TLS	session	caching	is turned off. See smtpd_tls_always_issue_ses-
       sion_ids	for further details.

       This feature is available in Postfix 2.8	and later.

tlsproxy_tls_ask_ccert (default: $smtpd_tls_ask_ccert)
       Ask  a	remote	 SMTP	client	 for   a   client   certificate.   See
       smtpd_tls_ask_ccert for further details.

       This feature is available in Postfix 2.8	and later.

tlsproxy_tls_ccert_verifydepth (default: $smtpd_tls_ccert_verifydepth)
       The  verification depth for remote SMTP client certificates. A depth of
       1 is sufficient if the issuing CA is listed in a	 local	CA  file.  See
       smtpd_tls_ccert_verifydepth for further details.

       This feature is available in Postfix 2.8	and later.

tlsproxy_tls_cert_file (default: $smtpd_tls_cert_file)
       File with the Postfix tlsproxy(8) server	RSA certificate	in PEM format.
       This file may also contain the Postfix tlsproxy(8) server  private  RSA
       key.  See smtpd_tls_cert_file for further details.  With	Postfix	>= 3.4
       the preferred way to configure tlsproxy server keys and certificates is
       via the "tlsproxy_tls_chain_files" parameter.

       This feature is available in Postfix 2.8	and later.

tlsproxy_tls_chain_files (default: $smtpd_tls_chain_files)
       Files  with  the	Postfix	tlsproxy(8) server keys	and certificate	chains
       in PEM format. See smtpd_tls_chain_files	for further details.

       This feature is available in Postfix 3.4	and later.

tlsproxy_tls_ciphers (default: $smtpd_tls_ciphers)
       The minimum TLS cipher grade that the Postfix tlsproxy(8)  server  will
       use  with  opportunistic	TLS encryption.	See smtpd_tls_ciphers for fur-
       ther details.

       This feature is available in Postfix 2.8	and later.

tlsproxy_tls_dcert_file	(default: $smtpd_tls_dcert_file)
       File with the Postfix tlsproxy(8) server	DSA certificate	in PEM format.
       This  file  may also contain the	Postfix	tlsproxy(8) server private DSA
       key.  DSA is obsolete and should	not be used.  See smtpd_tls_dcert_file
       for further details.

       This feature is available in Postfix 2.8	and later.

tlsproxy_tls_dh1024_param_file (default: $smtpd_tls_dh1024_param_file)
       File  with DH parameters	that the Postfix tlsproxy(8) server should use
       with non-export EDH ciphers. See	smtpd_tls_dh1024_param_file  for  fur-
       ther details.

       This feature is available in Postfix 2.8	and later.

tlsproxy_tls_dh512_param_file (default:	$smtpd_tls_dh512_param_file)
       File  with DH parameters	that the Postfix tlsproxy(8) server should use
       with export-grade EDH ciphers. See smtpd_tls_dh512_param_file for  fur-
       ther  details.	The  default SMTP server cipher	grade is "medium" with
       Postfix releases	after the middle of 2015, and as a result export-grade
       cipher suites are by default not	used.

       With  Postfix  >=  3.6  export-grade  Diffie-Hellman key	exchange is no
       longer supported, and this parameter is silently	ignored.

       This feature is available in Postfix 2.8	and later.

tlsproxy_tls_dkey_file (default: $smtpd_tls_dkey_file)
       File with the Postfix tlsproxy(8) server	DSA private key	in PEM format.
       This  file may be combined with the Postfix tlsproxy(8) server DSA cer-
       tificate	file specified with $smtpd_tls_dcert_file.   DSA  is  obsolete
       and should not be used.	See smtpd_tls_dkey_file	for further details.

       This feature is available in Postfix 2.8	and later.

tlsproxy_tls_eccert_file (default: $smtpd_tls_eccert_file)
       File  with the Postfix tlsproxy(8) server ECDSA certificate in PEM for-
       mat.  This file may also	contain	the Postfix tlsproxy(8)	server private
       ECDSA  key.  See	smtpd_tls_eccert_file for further details.  With Post-
       fix >= 3.4 the preferred	way to configure tlsproxy server keys and cer-
       tificates is via	the "tlsproxy_tls_chain_files" parameter.

       This feature is available in Postfix 2.8	and later.

tlsproxy_tls_eckey_file	(default: $smtpd_tls_eckey_file)
       File  with the Postfix tlsproxy(8) server ECDSA private key in PEM for-
       mat.  This file may be combined with  the  Postfix  tlsproxy(8)	server
       ECDSA  certificate  file	 specified  with  $smtpd_tls_eccert_file.  See
       smtpd_tls_eckey_file for	further	details.  With Postfix >= 3.4 the pre-
       ferred  way  to	configure tlsproxy server keys and certificates	is via
       the "tlsproxy_tls_chain_files" parameter.

       This feature is available in Postfix 2.8	and later.

tlsproxy_tls_eecdh_grade (default: $smtpd_tls_eecdh_grade)
       The Postfix tlsproxy(8) server  security	 grade	for  ephemeral	ellip-
       tic-curve      Diffie-Hellman	 (EECDH)     key     exchange.	   See
       smtpd_tls_eecdh_grade for further details.

       This feature is available in Postfix 2.8	and later.

tlsproxy_tls_exclude_ciphers (default: $smtpd_tls_exclude_ciphers)
       List of ciphers or cipher types to exclude from the tlsproxy(8)	server
       cipher  list  at	all TLS	security levels. See smtpd_tls_exclude_ciphers
       for further details.

       This feature is available in Postfix 2.8	and later.

tlsproxy_tls_fingerprint_digest	(default: $smtpd_tls_fingerprint_digest)
       The message digest algorithm to construct remote	 SMTP  client-certifi-
       cate  fingerprints.  See	 smtpd_tls_fingerprint_digest  for further de-
       tails.

       This feature is available in Postfix 2.8	and later.

tlsproxy_tls_key_file (default:	$smtpd_tls_key_file)
       File with the Postfix tlsproxy(8) server	RSA private key	in PEM format.
       This  file may be combined with the Postfix tlsproxy(8) server RSA cer-
       tificate	   file	   specified	with	$smtpd_tls_cert_file.	   See
       smtpd_tls_key_file  for	further	details.  With Postfix >= 3.4 the pre-
       ferred way to configure tlsproxy	server keys and	 certificates  is  via
       the "tlsproxy_tls_chain_files" parameter.

       This feature is available in Postfix 2.8	and later.

tlsproxy_tls_loglevel (default:	$smtpd_tls_loglevel)
       Enable  additional  Postfix tlsproxy(8) server logging of TLS activity.
       Each logging level also includes	the information	that is	 logged	 at  a
       lower logging level. See	smtpd_tls_loglevel for further details.

       This feature is available in Postfix 2.8	and later.

tlsproxy_tls_mandatory_ciphers (default: $smtpd_tls_mandatory_ciphers)
       The  minimum  TLS cipher	grade that the Postfix tlsproxy(8) server will
       use with	mandatory TLS encryption. See smtpd_tls_mandatory_ciphers  for
       further details.

       This feature is available in Postfix 2.8	and later.

tlsproxy_tls_mandatory_exclude_ciphers	  (default:   $smtpd_tls_mandatory_ex-
       clude_ciphers)
       Additional list of ciphers or cipher types  to  exclude	from  the  tl-
       sproxy(8)  server  cipher  list	at mandatory TLS security levels.  See
       smtpd_tls_mandatory_exclude_ciphers for further details.

       This feature is available in Postfix 2.8	and later.

tlsproxy_tls_mandatory_protocols (default: $smtpd_tls_mandatory_protocols)
       The SSL/TLS protocols accepted by the Postfix tlsproxy(8)  server  with
       mandatory TLS encryption. If the	list is	empty, the server supports all
       available SSL/TLS protocol versions.  See smtpd_tls_mandatory_protocols
       for further details.

       This feature is available in Postfix 2.8	and later.

tlsproxy_tls_protocols (default: $smtpd_tls_protocols)
       List  of	TLS protocols that the Postfix tlsproxy(8) server will exclude
       or include with opportunistic TLS encryption.  See  smtpd_tls_protocols
       for further details.

       This feature is available in Postfix 2.8	and later.

tlsproxy_tls_req_ccert (default: $smtpd_tls_req_ccert)
       With  mandatory	TLS  encryption,  require a trusted remote SMTP	client
       certificate  in	order  to  allow  TLS  connections  to	proceed.   See
       smtpd_tls_req_ccert for further details.

       This feature is available in Postfix 2.8	and later.

tlsproxy_tls_security_level (default: $smtpd_tls_security_level)
       The  SMTP TLS security level for	the Postfix tlsproxy(8)	server;	when a
       non-empty value is specified, this overrides  the  obsolete  parameters
       smtpd_use_tls  and  smtpd_enforce_tls. See smtpd_tls_security_level for
       further details.

       This feature is available in Postfix 2.8	and later.

tlsproxy_tls_session_cache_timeout (default: $smtpd_tls_session_cache_timeout)

       Obsolete	 expiration  time  of  Postfix	tlsproxy(8) server TLS session
       cache information. Since	the cache is shared with smtpd(8) and  managed
       by  tlsmgr(8),  there  is  only one expiration time for the SMTP	server
       cache   shared	by   all   three   services,   namely	smtpd_tls_ses-
       sion_cache_timeout.

       This feature is available in Postfix 2.8	and later.

tlsproxy_use_tls (default: $smtpd_use_tls)
       Opportunistic  TLS:  announce  STARTTLS support to remote SMTP clients,
       but do not require that clients use TLS encryption.  See	 smtpd_use_tls
       for further details. Use	tlsproxy_tls_security_level instead.

       This feature is available in Postfix 2.8	and later.

tlsproxy_watchdog_timeout (default: 10s)
       How much	time a tlsproxy(8) process may take to process local or	remote
       I/O before it is	terminated by a	built-in watchdog timer.   This	 is  a
       safety mechanism	that prevents tlsproxy(8) from becoming	non-responsive
       due to a	bug in Postfix itself or in system software.  To  avoid	 false
       alarms  and unnecessary cache corruption	this limit cannot be set under
       10s.

       Specify a non-zero time value  (an  integral  value  plus  an  optional
       one-letter  suffix  that	specifies the time unit).  Time	units: s (sec-
       onds), m	(minutes), h (hours), d	(days),	w (weeks).  The	 default  time
       unit is s (seconds).

       This feature is available in Postfix 2.8	and later

trace_service_name (default: trace)
       The  name  of  the  trace  service.  This service is implemented	by the
       bounce(8) daemon	and maintains a	record of mail deliveries and produces
       a  mail	delivery report	when verbose delivery is requested with	"send-
       mail -v".

       This feature is available in Postfix 2.1	and later.

transport_delivery_slot_cost (default: $default_delivery_slot_cost)
       A transport-specific override for the default_delivery_slot_cost	param-
       eter value, where transport is the master.cf name of the	message	deliv-
       ery transport.

       Note: transport_delivery_slot_cost  parameters  will  not  show	up  in
       "postconf"  command output before Postfix version 2.9.  This limitation
       applies to many parameters whose	name is	a combination of  a  master.cf
       service	 name	and   a	  built-in  suffix  (in	 this  case:  "_deliv-
       ery_slot_cost").

transport_delivery_slot_discount (default: $default_delivery_slot_discount)
       A transport-specific override  for  the	default_delivery_slot_discount
       parameter  value,  where	transport is the master.cf name	of the message
       delivery	transport.

       Note: transport_delivery_slot_discount parameters will not show	up  in
       "postconf"  command output before Postfix version 2.9.  This limitation
       applies to many parameters whose	name is	a combination of  a  master.cf
       service	name and a built-in suffix (in this case: "_delivery_slot_dis-
       count").

transport_delivery_slot_loan (default: $default_delivery_slot_loan)
       A transport-specific override for the default_delivery_slot_loan	param-
       eter value, where transport is the master.cf name of the	message	deliv-
       ery transport.

       Note: transport_delivery_slot_loan  parameters  will  not  show	up  in
       "postconf"  command output before Postfix version 2.9.  This limitation
       applies to many parameters whose	name is	a combination of  a  master.cf
       service	 name	and   a	  built-in  suffix  (in	 this  case:  "_deliv-
       ery_slot_loan").

transport_destination_concurrency_failed_cohort_limit (default:	 $default_des-
       tination_concurrency_failed_cohort_limit)
       A   transport-specific  override	 for  the  default_destination_concur-
       rency_failed_cohort_limit parameter value, where	transport is the  mas-
       ter.cf name of the message delivery transport.

       Note: some transport_destination_concurrency_failed_cohort_limit	param-
       eters will not show up in "postconf" command output before Postfix ver-
       sion  2.9.   This limitation applies to many parameters whose name is a
       combination of a	master.cf service name and a built-in suffix (in  this
       case: "_destination_concurrency_failed_cohort_limit").

       This feature is available in Postfix 2.5	and later.

transport_destination_concurrency_limit	(default: $default_destination_concur-
       rency_limit)
       A  transport-specific  override	for  the   default_destination_concur-
       rency_limit  parameter  value, where transport is the master.cf name of
       the message delivery transport.

       Note: some transport_destination_concurrency_limit parameters will  not
       show  up	in "postconf" command output before Postfix version 2.9.  This
       limitation applies to many parameters whose name	is a combination of  a
       master.cf  service name and a built-in suffix (in this case: "_destina-
       tion_concurrency_limit").

transport_destination_concurrency_negative_feedback (default:  $default_desti-
       nation_concurrency_negative_feedback)
       A   transport-specific  override	 for  the  default_destination_concur-
       rency_negative_feedback parameter value,	where transport	 is  the  mas-
       ter.cf name of the message delivery transport.

       Note:  some transport_destination_concurrency_negative_feedback parame-
       ters will not show up in	"postconf" command output before Postfix  ver-
       sion  2.9.   This limitation applies to many parameters whose name is a
       combination of a	master.cf service name and a built-in suffix (in  this
       case: "_destination_concurrency_negative_feedback").

       This feature is available in Postfix 2.5	and later.

transport_destination_concurrency_positive_feedback  (default: $default_desti-
       nation_concurrency_positive_feedback)
       A  transport-specific  override	for  the   default_destination_concur-
       rency_positive_feedback	parameter  value,  where transport is the mas-
       ter.cf name of the message delivery transport.

       Note: some transport_destination_concurrency_positive_feedback  parame-
       ters  will not show up in "postconf" command output before Postfix ver-
       sion 2.9.  This limitation applies to many parameters whose name	 is  a
       combination  of a master.cf service name	and a built-in suffix (in this
       case: "_destination_concurrency_positive_feedback").

       This feature is available in Postfix 2.5	and later.

transport_destination_rate_delay (default: $default_destination_rate_delay)
       A transport-specific override  for  the	default_destination_rate_delay
       parameter  value,  where	transport is the master.cf name	of the message
       delivery	transport.

       Note: some transport_destination_rate_delay parameters will not show up
       in  "postconf" command output before Postfix version 2.9.  This limita-
       tion applies to many parameters whose name is a combination of  a  mas-
       ter.cf  service	name  and  a built-in suffix (in this case: "_destina-
       tion_rate_delay").

       This feature is available in Postfix 2.5	and later.

transport_destination_recipient_limit  (default:  $default_destination_recipi-
       ent_limit)
       A   transport-specific  override	 for  the  default_destination_recipi-
       ent_limit parameter value, where	transport is the master.cf name	of the
       message delivery	transport.

       Note:  some  transport_destination_recipient_limit  parameters will not
       show up in "postconf" command output before Postfix version 2.9.	  This
       limitation  applies to many parameters whose name is a combination of a
       master.cf service name and a built-in suffix (in	this case:  "_destina-
       tion_recipient_limit").

transport_extra_recipient_limit	(default: $default_extra_recipient_limit)
       A transport-specific override for the default_extra_recipient_limit pa-
       rameter value, where transport is the master.cf name of the message de-
       livery transport.

       Note:  transport_extra_recipient_limit  parameters  will	not show up in
       "postconf" command output before	Postfix	version	2.9.  This  limitation
       applies	to  many parameters whose name is a combination	of a master.cf
       service name and	a  built-in  suffix  (in  this	case:  "_extra_recipi-
       ent_limit").

transport_initial_destination_concurrency  (default: $initial_destination_con-
       currency)
       A transport-specific override for  the  initial_destination_concurrency
       parameter  value,  where	transport is the master.cf name	of the message
       delivery	transport.

       Note: some  transport_initial_destination_concurrency  parameters  will
       not  show  up  in "postconf" command output before Postfix version 2.9.
       This limitation applies to many parameters whose	name is	a  combination
       of a master.cf service name and a built-in suffix (in this case:	"_ini-
       tial_destination_concurrency").

       This feature is available in Postfix 2.5	and later.

transport_maps (default: empty)
       Optional	lookup tables with mappings from recipient address to (message
       delivery	 transport,  next-hop  destination).  See transport(5) for de-
       tails.

       Specify zero or more "type:table" lookup	tables,	 separated  by	white-
       space  or comma.	Tables will be searched	in the specified order until a
       match is	found.	If you use this	feature	with local files, run "postmap
       /usr/local/etc/postfix/transport" after making a	change.

       Pattern	matching  of domain names is controlled	by the presence	or ab-
       sence of	"transport_maps" in the	 parent_domain_matches_subdomains  pa-
       rameter value.

       For safety reasons, as of Postfix 2.3 this feature does not allow $num-
       ber substitutions in regular expression maps.

       Examples:

       transport_maps =	dbm:$config_directory/transport
       transport_maps =	hash:$config_directory/transport

transport_minimum_delivery_slots (default: $default_minimum_delivery_slots)
       A transport-specific override  for  the	default_minimum_delivery_slots
       parameter  value,  where	transport is the master.cf name	of the message
       delivery	transport.

       Note: transport_minimum_delivery_slots parameters will not show	up  in
       "postconf"  command output before Postfix version 2.9.  This limitation
       applies to many parameters whose	name is	a combination of  a  master.cf
       service	name  and  a  built-in	suffix (in this	case: "_minimum_deliv-
       ery_slots").

transport_recipient_limit (default: $default_recipient_limit)
       A transport-specific override for the default_recipient_limit parameter
       value,  where  transport	 is the	master.cf name of the message delivery
       transport.

       Note: some transport_recipient_limit parameters will  not  show	up  in
       "postconf"  command output before Postfix version 2.9.  This limitation
       applies to many parameters whose	name is	a combination of  a  master.cf
       service name and	a built-in suffix (in this case: "_recipient_limit").

transport_recipient_refill_delay (default: $default_recipient_refill_delay)
       A  transport-specific  override	for the	default_recipient_refill_delay
       parameter value,	where transport	is the master.cf name of  the  message
       delivery	transport.

       Note:  transport_recipient_refill_delay	parameters will	not show up in
       "postconf" command output before	Postfix	version	2.9.  This  limitation
       applies	to  many parameters whose name is a combination	of a master.cf
       service name and	a  built-in  suffix  (in  this	case:  "_recipient_re-
       fill_delay").

       This feature is available in Postfix 2.4	and later.

transport_recipient_refill_limit (default: $default_recipient_refill_limit)
       A  transport-specific  override	for the	default_recipient_refill_limit
       parameter value,	where transport	is the master.cf name of  the  message
       delivery	transport.

       Note:  transport_recipient_refill_limit	parameters will	not show up in
       "postconf" command output before	Postfix	version	2.9.  This  limitation
       applies	to  many parameters whose name is a combination	of a master.cf
       service name and	a  built-in  suffix  (in  this	case:  "_recipient_re-
       fill_limit").

       This feature is available in Postfix 2.4	and later.

transport_retry_time (default: 60s)
       The  time  between  attempts  by	the Postfix queue manager to contact a
       malfunctioning message delivery transport.

       Specify a non-zero time value  (an  integral  value  plus  an  optional
       one-letter  suffix  that	specifies the time unit).  Time	units: s (sec-
       onds), m	(minutes), h (hours), d	(days),	w (weeks).  The	 default  time
       unit is s (seconds).

transport_time_limit (default: $command_time_limit)
       A  transport-specific  override	for  the  command_time_limit parameter
       value, where transport is the master.cf name of	the  message  delivery
       transport.

       Specify	a  non-zero  time  value  (an  integral	value plus an optional
       one-letter suffix that specifies	the time unit).	 Time units:  s	 (sec-
       onds),  m  (minutes), h (hours),	d (days), w (weeks).  The default time
       unit is s (seconds).

       Note: transport_time_limit parameters will not show  up	in  "postconf"
       command	output before Postfix version 2.9.  This limitation applies to
       many parameters whose name is a combination of a	master.cf service name
       and a built-in suffix (in this case: "_time_limit").

transport_transport_rate_delay (default: $default_transport_rate_delay)
       A  transport-specific override for the default_transport_rate_delay pa-
       rameter value, where the	initial	transport in the parameter name	is the
       master.cf name of the message delivery transport.

       Specify	a  non-negative	time value (an integral	value plus an optional
       one-letter suffix that specifies	the time unit).	 Time units:  s	 (sec-
       onds),  m  (minutes), h (hours),	d (days), w (weeks).  The default time
       unit is s (seconds).

       Note: transport_transport_rate_delay parameters will  not  show	up  in
       "postconf"  command output before Postfix version 2.9.  This limitation
       applies to many parameters whose	name is	a combination of  a  master.cf
       service	name and a built-in suffix (in this case: "_transport_rate_de-
       lay").

trigger_timeout	(default: 10s)
       The time	limit for sending a trigger to a Postfix daemon	(for  example,
       the  pickup(8)  or  qmgr(8)  daemon). This time limit prevents programs
       from getting stuck when the mail	system is under	heavy load.

       Specify a non-zero time value  (an  integral  value  plus  an  optional
       one-letter  suffix  that	specifies the time unit).  Time	units: s (sec-
       onds), m	(minutes), h (hours), d	(days),	w (weeks).  The	 default  time
       unit is s (seconds).

undisclosed_recipients_header (default:	see postconf -d	output)
       Message	header	that the Postfix cleanup(8) server inserts when	a mes-
       sage contains no	To: or Cc: message header. With	Postfix	2.8 and	later,
       the  default  value  is	empty.	With Postfix 2.4-2.7, specify an empty
       value to	disable	this feature.

       Example:

       # Default value before Postfix 2.8.
       # Note: the ":" and ";" are both	required.
       undisclosed_recipients_header = To: undisclosed-recipients:;

unknown_address_reject_code (default: 450)
       The numerical response code when	the  Postfix  SMTP  server  rejects  a
       sender or recipient address because its domain is unknown.  This	is one
       of the possible replies from the	restrictions reject_unknown_sender_do-
       main and	reject_unknown_recipient_domain.

       Do  not	change	this  unless  you have a complete understanding	of RFC
       5321.

unknown_address_tempfail_action	(default: $reject_tempfail_action)
       The Postfix SMTP	server's action	when  reject_unknown_sender_domain  or
       reject_unknown_recipient_domain	fail  due  to a	temporary error	condi-
       tion. Specify "defer" to	defer the remote SMTP client  request  immedi-
       ately.  With  the  default  "defer_if_permit"  action, the Postfix SMTP
       server continues	to look	for opportunities to reject mail,  and	defers
       the client request only if it would otherwise be	accepted.

       This feature is available in Postfix 2.6	and later.

unknown_client_reject_code (default: 450)
       The  numerical  Postfix SMTP server response code when a	client without
       valid  address  <=>  name  mapping  is  rejected	 by   the   reject_un-
       known_client_hostname  restriction. The SMTP server always replies with
       450 when	the mapping failed due to a temporary error condition.

       Do not change this unless you have  a  complete	understanding  of  RFC
       5321.

unknown_helo_hostname_tempfail_action (default:	$reject_tempfail_action)
       The  Postfix  SMTP  server's  action  when reject_unknown_helo_hostname
       fails due to a temporary	error condition. Specify "defer" to defer  the
       remote SMTP client request immediately. With the	default	"defer_if_per-
       mit" action, the	Postfix	SMTP server continues to look  for  opportuni-
       ties  to	 reject	 mail,	and defers the client request only if it would
       otherwise be accepted.

       This feature is available in Postfix 2.6	and later.

unknown_hostname_reject_code (default: 450)
       The numerical Postfix SMTP server response code when the	hostname spec-
       ified  with  the	 HELO  or  EHLO	 command is rejected by	the reject_un-
       known_helo_hostname restriction.

       Do not change this unless you have  a  complete	understanding  of  RFC
       5321.

unknown_local_recipient_reject_code (default: 550)
       The  numerical  Postfix	SMTP server response code when a recipient ad-
       dress is	local, and $local_recipient_maps specifies a  list  of	lookup
       tables that does	not match the recipient.  A recipient address is local
       when its	domain matches $mydestination, $proxy_interfaces or  $inet_in-
       terfaces.

       The  default  setting is	550 (reject mail) but it is safer to initially
       use 450 (try again later) so you	have time to  find  out	 if  your  lo-
       cal_recipient_maps settings are OK.

       Example:

       unknown_local_recipient_reject_code = 450

       This feature is available in Postfix 2.0	and later.

unknown_relay_recipient_reject_code (default: 550)
       The  numerical  Postfix SMTP server reply code when a recipient address
       matches $relay_domains, and relay_recipient_maps	specifies  a  list  of
       lookup tables that does not match the recipient address.

       This feature is available in Postfix 2.0	and later.

unknown_virtual_alias_reject_code (default: 550)
       The  Postfix  SMTP  server  reply code when a recipient address matches
       $virtual_alias_domains, and $virtual_alias_maps	specifies  a  list  of
       lookup tables that does not match the recipient address.

       This feature is available in Postfix 2.0	and later.

unknown_virtual_mailbox_reject_code (default: 550)
       The  Postfix  SMTP  server  reply code when a recipient address matches
       $virtual_mailbox_domains, and $virtual_mailbox_maps specifies a list of
       lookup tables that does not match the recipient address.

       This feature is available in Postfix 2.0	and later.

unverified_recipient_defer_code	(default: 450)
       The  numerical  Postfix	SMTP  server response when a recipient address
       probe fails due to a temporary error condition.

       Unlike elsewhere	in Postfix, you	can specify 250	in order to accept the
       address anyway.

       Do  not	change	this  unless  you have a complete understanding	of RFC
       5321.

       This feature is available in Postfix 2.6	and later.

unverified_recipient_reject_code (default: 450)
       The numerical Postfix SMTP server response when a recipient address  is
       rejected	by the reject_unverified_recipient restriction.

       Unlike elsewhere	in Postfix, you	can specify 250	in order to accept the
       address anyway.

       Do not change this unless you have  a  complete	understanding  of  RFC
       5321.

       This feature is available in Postfix 2.1	and later.

unverified_recipient_reject_reason (default: empty)
       The Postfix SMTP	server's reply when rejecting mail with	reject_unveri-
       fied_recipient. Do not include the numeric SMTP reply code or  the  en-
       hanced  status  code.  By default, the response includes	actual address
       verification details.

       Example:

       unverified_recipient_reject_reason = Recipient address lookup failed

       This feature is available in Postfix 2.6	and later.

unverified_recipient_tempfail_action (default: $reject_tempfail_action)
       The Postfix SMTP	server's action	when reject_unverified_recipient fails
       due to a	temporary error	condition. Specify "defer" to defer the	remote
       SMTP client request immediately.	With the default "defer_if_permit" ac-
       tion,  the  Postfix  SMTP server	continues to look for opportunities to
       reject mail, and	defers the client request only if it  would  otherwise
       be accepted.

       This feature is available in Postfix 2.6	and later.

unverified_sender_defer_code (default: 450)
       The  numerical  Postfix SMTP server response code when a	sender address
       probe fails due to a temporary error condition.

       Unlike elsewhere	in Postfix, you	can specify 250	in order to accept the
       address anyway.

       Do  not	change	this  unless  you have a complete understanding	of RFC
       5321.

       This feature is available in Postfix 2.6	and later.

unverified_sender_reject_code (default:	450)
       The numerical Postfix SMTP server response code when  a	recipient  ad-
       dress is	rejected by the	reject_unverified_sender restriction.

       Unlike elsewhere	in Postfix, you	can specify 250	in order to accept the
       address anyway.

       Do not change this unless you have  a  complete	understanding  of  RFC
       5321.

       This feature is available in Postfix 2.1	and later.

unverified_sender_reject_reason	(default: empty)
       The Postfix SMTP	server's reply when rejecting mail with	reject_unveri-
       fied_sender. Do not include the numeric SMTP reply code or the enhanced
       status code. By default,	the response includes actual address verifica-
       tion details.

       Example:

       unverified_sender_reject_reason = Sender	address	lookup failed

       This feature is available in Postfix 2.6	and later.

unverified_sender_tempfail_action (default: $reject_tempfail_action)
       The Postfix SMTP	server's action	 when  reject_unverified_sender	 fails
       due to a	temporary error	condition. Specify "defer" to defer the	remote
       SMTP client request immediately.	With the default "defer_if_permit" ac-
       tion,  the  Postfix  SMTP server	continues to look for opportunities to
       reject mail, and	defers the client request only if it  would  otherwise
       be accepted.

       This feature is available in Postfix 2.6	and later.

verp_delimiter_filter (default:	-=+)
       The  characters	Postfix	 accepts  as  VERP delimiter characters	on the
       Postfix sendmail(1) command line	and in SMTP commands.

       This feature is available in Postfix 1.1	and later.

virtual_alias_address_length_limit (default: 1000)
       The maximal length of an	email address after virtual  alias  expansion.
       This  stops virtual aliasing loops that increase	the address length ex-
       ponentially.

       This feature is available in Postfix 3.0	and later.

virtual_alias_domains (default:	$virtual_alias_maps)
       Postfix is the final destination	for  the  specified  list  of  virtual
       alias  domains, that is,	domains	for which all addresses	are aliased to
       addresses in other local	or remote domains. The SMTP  server  validates
       recipient  addresses  with $virtual_alias_maps and rejects non-existent
       recipients. See	also  the  virtual  alias  domain  class  in  the  AD-
       DRESS_CLASS_README file

       This  feature  is available in Postfix 2.0 and later. The default value
       is backwards compatible with Postfix version 1.1.

       The default value is $virtual_alias_maps	so that	you can	keep  all  in-
       formation  about	 virtual alias domains in one place.  If you have many
       users, it is better to separate	information  that  changes  more  fre-
       quently	(virtual  address -> local or remote address mapping) from in-
       formation that changes less frequently  (the  list  of  virtual	domain
       names).

       Specify	a  list	 of host or domain names, "/file/name" or "type:table"
       patterns, separated by commas and/or whitespace.	A "/file/name" pattern
       is  replaced  by	 its  contents;	a "type:table" lookup table is matched
       when a table entry matches a host or domain name	(the lookup result  is
       ignored).   Continue  long  lines by starting the next line with	white-
       space. Specify "!pattern" to exclude a host or  domain  name  from  the
       list.  The  form	"!/file/name" is supported only	in Postfix version 2.4
       and later.

       See also	the VIRTUAL_README and ADDRESS_CLASS_README documents for fur-
       ther information.

       Example:

       virtual_alias_domains = virtual1.tld virtual2.tld

virtual_alias_expansion_limit (default:	1000)
       The  maximal  number of addresses that virtual alias expansion produces
       from each original recipient.

       This feature is available in Postfix 2.1	and later.

virtual_alias_maps (default: $virtual_maps)
       Optional	lookup tables that alias specific mail addresses or domains to
       other local or remote addresses.	 The table format and lookups are doc-
       umented in virtual(5). For an overview of Postfix address manipulations
       see the ADDRESS_REWRITING_README	document.

       This  feature  is available in Postfix 2.0 and later. The default value
       is backwards compatible with Postfix version 1.1.

       Specify zero or more "type:name"	lookup tables, separated by whitespace
       or  comma. Tables will be searched in the specified order until a match
       is found.  Note:	these lookups are recursive.

       If you use this feature	with  indexed  files,  run  "postmap  /usr/lo-
       cal/etc/postfix/virtual"	after changing the file.

       Examples:

       virtual_alias_maps = dbm:$config_directory/virtual
       virtual_alias_maps = hash:$config_directory/virtual

virtual_alias_recursion_limit (default:	1000)
       The  maximal  nesting  depth of virtual alias expansion.	 Currently the
       recursion limit is applied only to the left  branch  of	the  expansion
       graph,  so the depth of the tree	can in the worst case reach the	sum of
       the expansion and recursion limits.  This may change in the future.

       This feature is available in Postfix 2.1	and later.

virtual_delivery_status_filter (default: $default_delivery_status_filter)
       Optional	filter for the virtual(8) delivery agent to change the	deliv-
       ery  status  code or explanatory	text of	successful or unsuccessful de-
       liveries.  See default_delivery_status_filter for details.

       This feature is available in Postfix 3.0	and later.

virtual_destination_concurrency_limit  (default:  $default_destination_concur-
       rency_limit)
       The  maximal  number of parallel	deliveries to the same destination via
       the virtual message delivery transport. This limit is enforced  by  the
       queue  manager.	The message delivery transport name is the first field
       in the entry in the master.cf file.

virtual_destination_recipient_limit   (default:	  $default_destination_recipi-
       ent_limit)
       The  maximal  number  of	recipients per message for the virtual message
       delivery	transport. This	limit is enforced by the  queue	 manager.  The
       message	delivery transport name	is the first field in the entry	in the
       master.cf file.

       Setting this parameter to a value of 1  changes	the  meaning  of  vir-
       tual_destination_concurrency_limit  from	 concurrency  per  domain into
       concurrency per recipient.

virtual_gid_maps (default: empty)
       Lookup tables with the per-recipient group ID  for  virtual(8)  mailbox
       delivery.

       This  parameter	is specific to the virtual(8) delivery agent.  It does
       not apply when mail is delivered	with a different  mail	delivery  pro-
       gram.

       Specify zero or more "type:name"	lookup tables, separated by whitespace
       or comma. Tables	will be	searched in the	specified order	until a	 match
       is found.

       In  a  lookup table, specify a left-hand	side of	"@domain.tld" to match
       any user	in  the	 specified  domain  that  does	not  have  a  specific
       "user@domain.tld" entry.

       When   a	  recipient   address	has   an  optional  address  extension
       (user+foo@domain.tld), the virtual(8) delivery agent looks up the  full
       address	first,	and  when the lookup fails, it looks up	the unextended
       address (user@domain.tld).

       Note 1: for security reasons, the virtual(8) delivery  agent  disallows
       regular expression substitution of $1 etc. in regular expression	lookup
       tables, because that would open a security hole.

       Note 2: for  security  reasons,	the  virtual(8)	 delivery  agent  will
       silently	ignore requests	to use the proxymap(8) server. Instead it will
       open the	table directly.	Before Postfix version 2.2, the	virtual(8) de-
       livery agent will terminate with	a fatal	error.

virtual_mailbox_base (default: empty)
       A  prefix  that	the virtual(8) delivery	agent prepends to all pathname
       results from $virtual_mailbox_maps table	lookups.   This	 is  a	safety
       measure	to  ensure  that an out	of control map doesn't litter the file
       system with mailboxes.  While virtual_mailbox_base could	be set to "/",
       this setting isn't recommended.

       This  parameter	is specific to the virtual(8) delivery agent.  It does
       not apply when mail is delivered	with a different  mail	delivery  pro-
       gram.

       Example:

       virtual_mailbox_base = /var/mail

virtual_mailbox_domains	(default: $virtual_mailbox_maps)
       Postfix	is  the	 final	destination for	the specified list of domains;
       mail is delivered via the $virtual_transport mail  delivery  transport.
       By  default  this  is  the Postfix virtual(8) delivery agent.  The SMTP
       server validates	recipient addresses with $virtual_mailbox_maps and re-
       jects  mail  for	non-existent recipients.  See also the virtual mailbox
       domain class in the ADDRESS_CLASS_README	file.

       This parameter expects the same syntax as the mydestination  configura-
       tion parameter.

       This  feature  is available in Postfix 2.0 and later. The default value
       is backwards compatible with Postfix version 1.1.

virtual_mailbox_limit (default:	51200000)
       The maximal size	in  bytes  of  an  individual  virtual(8)  mailbox  or
       maildir file, or	zero (no limit).

       This  parameter	is specific to the virtual(8) delivery agent.  It does
       not apply when mail is delivered	with a different  mail	delivery  pro-
       gram.

virtual_mailbox_lock (default: see postconf -d output)
       How to lock a UNIX-style	virtual(8) mailbox before attempting delivery.
       For a list of available file locking methods,  use  the	"postconf  -l"
       command.

       This  parameter	is specific to the virtual(8) delivery agent.  It does
       not apply when mail is delivered	with a different  mail	delivery  pro-
       gram.

       This  setting  is ignored with maildir style delivery, because such de-
       liveries	are safe without application-level locks.

       Note 1: the dotlock method requires that	the recipient UID or  GID  has
       write access to the parent directory of the recipient's mailbox file.

       Note 2: the default setting of this parameter is	system dependent.

virtual_mailbox_maps (default: empty)
       Optional	 lookup	 tables	 with  all valid addresses in the domains that
       match $virtual_mailbox_domains.

       Specify zero or more "type:name"	lookup tables, separated by whitespace
       or  comma. Tables will be searched in the specified order until a match
       is found.

       In a lookup table, specify a left-hand side of "@domain.tld"  to	 match
       any  user  in  the  specified  domain  that  does  not  have a specific
       "user@domain.tld" entry.

       With the	 default  "virtual_mailbox_domains  =  $virtual_mailbox_maps",
       lookup  tables  also need entries with a	left-hand side of "domain.tld"
       to satisfy virtual_mailbox_domain lookups (the right-hand side  is  re-
       quired but will not be used).

       The  remainder  of  this	 text  is  specific to the virtual(8) delivery
       agent.  It does not apply when mail is delivered	with a different  mail
       delivery	program.

       The virtual(8) delivery agent uses this table to	look up	the per-recip-
       ient mailbox or maildir pathname.  If the lookup	result ends in a slash
       ("/"), maildir-style delivery is	carried	out, otherwise the path	is as-
       sumed to	specify	a UNIX-style mailbox file.  Note  that	$virtual_mail-
       box_base	is unconditionally prepended to	this path.

       When   a	  recipient   address	has   an  optional  address  extension
       (user+foo@domain.tld), the virtual(8) delivery agent looks up the  full
       address	first,	and  when the lookup fails, it looks up	the unextended
       address (user@domain.tld).

       Note 1: for security reasons, the virtual(8) delivery  agent  disallows
       regular expression substitution of $1 etc. in regular expression	lookup
       tables, because that would open a security hole.

       Note 2: for  security  reasons,	the  virtual(8)	 delivery  agent  will
       silently	ignore requests	to use the proxymap(8) server. Instead it will
       open the	table directly.	Before Postfix version 2.2, the	virtual(8) de-
       livery agent will terminate with	a fatal	error.

virtual_maps (default: empty)
       Optional	lookup tables with a) names of domains for which all addresses
       are aliased to addresses	in other local or remote domains, and  b)  ad-
       dresses that are	aliased	to addresses in	other local or remote domains.
       Available before	Postfix	version	2.0.  With  Postfix  version  2.0  and
       later, this is replaced by separate controls: virtual_alias_domains and
       virtual_alias_maps.

virtual_minimum_uid (default: 100)
       The minimum user	ID value that the virtual(8) delivery agent accepts as
       a  result  from	$virtual_uid_maps  table lookup.  Returned values less
       than this will be rejected, and the message will	be deferred.

       This parameter is specific to the virtual(8) delivery agent.   It  does
       not  apply  when	 mail is delivered with	a different mail delivery pro-
       gram.

virtual_transport (default: virtual)
       The default mail	delivery transport and next-hop	destination for	 final
       delivery	 to domains listed with	$virtual_mailbox_domains.  This	infor-
       mation can be overruled with the	transport(5) table.

       Specify a string	of the form transport:nexthop, where transport is  the
       name  of	 a mail	delivery transport defined in master.cf.  The :nexthop
       destination is optional;	its syntax is documented in the	manual page of
       the corresponding delivery agent.

       This feature is available in Postfix 2.0	and later.

virtual_uid_maps (default: empty)
       Lookup tables with the per-recipient user ID that the virtual(8)	deliv-
       ery agent uses while writing to the recipient's mailbox.

       This parameter is specific to the virtual(8) delivery agent.   It  does
       not  apply  when	 mail is delivered with	a different mail delivery pro-
       gram.

       Specify zero or more "type:name"	lookup tables, separated by whitespace
       or  comma. Tables will be searched in the specified order until a match
       is found.

       In a lookup table, specify a left-hand side of "@domain.tld"  to	 match
       any  user  in  the  specified  domain  that  does  not  have a specific
       "user@domain.tld" entry.

       When  a	recipient  address   has   an	optional   address   extension
       (user+foo@domain.tld),  the virtual(8) delivery agent looks up the full
       address first, and when the lookup fails, it looks  up  the  unextended
       address (user@domain.tld).

       Note  1:	 for security reasons, the virtual(8) delivery agent disallows
       regular expression substitution of $1 etc. in regular expression	lookup
       tables, because that would open a security hole.

       Note  2:	 for  security	reasons,  the  virtual(8)  delivery agent will
       silently	ignore requests	to use the proxymap(8) server. Instead it will
       open the	table directly.	Before Postfix version 2.2, the	virtual(8) de-
       livery agent will terminate with	a fatal	error.

SEE ALSO
       postconf(1), Postfix configuration parameter maintenance
       master(5), Postfix daemon configuration maintenance

LICENSE
       The Secure Mailer license must be distributed with this software.

AUTHOR(S)
       Wietse Venema
       IBM T.J.	Watson Research
       P.O. Box	704
       Yorktown	Heights, NY 10598, USA

       Wietse Venema
       Google, Inc.
       111 8th Avenue
       New York, NY 10011, USA

       Viktor Dukhovni

								   POSTCONF(5)

NAME | SYNOPSIS | DESCRIPTION | 2bounce_notice_recipient (default: postmaster) | access_map_defer_code (default: 450) | access_map_reject_code (default: 554) | address_verify_cache_cleanup_interval (default: 12h) | address_verify_default_transport (default: $default_transport) | address_verify_local_transport (default: $local_transport) | address_verify_map (default: see postconf -d output) | address_verify_negative_cache (default: yes) | address_verify_negative_expire_time (default: 3d) | address_verify_negative_refresh_time (default: 3h) | address_verify_pending_request_limit (default: see postconf -d output) | address_verify_poll_count (default: normal: 3, overload: 1) | address_verify_poll_delay (default: 3s) | address_verify_positive_expire_time (default: 31d) | address_verify_positive_refresh_time (default: 7d) | address_verify_relay_transport (default: $relay_transport) | address_verify_relayhost (default: $relayhost) | address_verify_sender (default: $double_bounce_sender) | address_verify_sender_dependent_default_transport_maps (default: $sender_de- | address_verify_sender_dependent_relayhost_maps (default: $sender_dependent_re- | address_verify_sender_ttl (default: 0s) | address_verify_service_name (default: verify) | address_verify_transport_maps (default: $transport_maps) | address_verify_virtual_transport (default: $virtual_transport) | alias_database (default: see postconf -d output) | alias_maps (default: see postconf -d output) | allow_mail_to_commands (default: alias, forward) | allow_mail_to_files (default: alias, forward) | allow_min_user (default: no) | allow_percent_hack (default: yes) | allow_untrusted_routing (default: no) | alternate_config_directories (default: empty) | always_add_missing_headers (default: no) | always_bcc (default: empty) | anvil_rate_time_unit (default: 60s) | anvil_status_update_time (default: 600s) | append_at_myorigin (default: yes) | append_dot_mydomain (default: Postfix >= 3.0: no, Postfix < 3.0: yes) | application_event_drain_time (default: 100s) | authorized_flush_users (default: static:anyone) | authorized_mailq_users (default: static:anyone) | authorized_submit_users (default: static:anyone) | authorized_verp_clients (default: $mynetworks) | backwards_bounce_logfile_compatibility (default: yes) | berkeley_db_create_buffer_size (default: 16777216) | berkeley_db_read_buffer_size (default: 131072) | best_mx_transport (default: empty) | biff (default: yes) | body_checks (default: empty) | body_checks_size_limit (default: 51200) | bounce_notice_recipient (default: postmaster) | bounce_queue_lifetime (default: 5d) | bounce_service_name (default: bounce) | bounce_size_limit (default: 50000) | bounce_template_file (default: empty) | broken_sasl_auth_clients (default: no) | canonical_classes (default: envelope_sender, envelope_recipient, | canonical_maps (default: empty) | cleanup_service_name (default: cleanup) | command_directory (default: see postconf -d output) | command_execution_directory (default: empty) | command_expansion_filter (default: see postconf -d output) | command_time_limit (default: 1000s) | compatibility_level (default: 0) | config_directory (default: see postconf -d output) | confirm_delay_cleared (default: no) | connection_cache_protocol_timeout (default: 5s) | connection_cache_service_name (default: scache) | connection_cache_status_update_time (default: 600s) | connection_cache_ttl_limit (default: 2s) | content_filter (default: empty) | cyrus_sasl_config_path (default: empty) | daemon_directory (default: see postconf -d output) | daemon_table_open_error_is_fatal (default: no) | daemon_timeout (default: 18000s) | data_directory (default: see postconf -d output) | debug_peer_level (default: 2) | debug_peer_list (default: empty) | debugger_command (default: empty) | default_database_type (default: see postconf -d output) | default_delivery_slot_cost (default: 5) | default_delivery_slot_discount (default: 50) | default_delivery_slot_loan (default: 3) | default_delivery_status_filter (default: empty) | default_destination_concurrency_failed_cohort_limit (default: 1) | default_destination_concurrency_limit (default: 20) | default_destination_concurrency_negative_feedback (default: 1) | default_destination_concurrency_positive_feedback (default: 1) | default_destination_rate_delay (default: 0s) | default_destination_recipient_limit (default: 50) | default_extra_recipient_limit (default: 1000) | default_filter_nexthop (default: empty) | default_minimum_delivery_slots (default: 3) | default_privs (default: nobody) | default_process_limit (default: 100) | default_rbl_reply (default: see postconf -d output) | default_recipient_limit (default: 20000) | default_recipient_refill_delay (default: 5s) | default_recipient_refill_limit (default: 100) | default_transport (default: smtp) | default_transport_rate_delay (default: 0s) | default_verp_delimiters (default: +=) | defer_code (default: 450) | defer_service_name (default: defer) | defer_transports (default: empty) | delay_logging_resolution_limit (default: 2) | delay_notice_recipient (default: postmaster) | delay_warning_time (default: 0h) | deliver_lock_attempts (default: 20) | deliver_lock_delay (default: 1s) | destination_concurrency_feedback_debug (default: no) | detect_8bit_encoding_header (default: yes) | disable_dns_lookups (default: no) | disable_mime_input_processing (default: no) | disable_mime_output_conversion (default: no) | disable_verp_bounces (default: no) | disable_vrfy_command (default: no) | dns_ncache_ttl_fix_enable (default: no) | dnsblog_reply_delay (default: 0s) | dnsblog_service_name (default: dnsblog) | dnssec_probe (default: ns:.) | dont_remove (default: 0) | double_bounce_sender (default: double-bounce) | duplicate_filter_limit (default: 1000) | empty_address_default_transport_maps_lookup_key (default: <>) | empty_address_local_login_sender_maps_lookup_key (default: <>) | empty_address_recipient (default: MAILER-DAEMON) | empty_address_relayhost_maps_lookup_key (default: <>) | enable_errors_to (default: no) | enable_idna2003_compatibility (default: no) | enable_long_queue_ids (default: no) | enable_original_recipient (default: yes) | enable_threaded_bounces (default: no) | error_notice_recipient (default: postmaster) | error_service_name (default: error) | execution_directory_expansion_filter (default: see postconf -d output) | expand_owner_alias (default: no) | export_environment (default: see postconf -d output) | extract_recipient_limit (default: 10240) | fallback_relay (default: empty) | fallback_transport (default: empty) | fallback_transport_maps (default: empty) | fast_flush_domains (default: $relay_domains) | fast_flush_purge_time (default: 7d) | fast_flush_refresh_time (default: 12h) | fault_injection_code (default: 0) | flush_service_name (default: flush) | fork_attempts (default: 5) | fork_delay (default: 1s) | forward_expansion_filter (default: see postconf -d output) | forward_path (default: see postconf -d output) | frozen_delivered_to (default: yes) | hash_queue_depth (default: 1) | hash_queue_names (default: deferred, defer) | header_address_token_limit (default: 10240) | header_checks (default: empty) | header_from_format (default: standard) | header_size_limit (default: 102400) | helpful_warnings (default: yes) | home_mailbox (default: empty) | hopcount_limit (default: 50) | html_directory (default: see postconf -d output) | ignore_mx_lookup_error (default: no) | import_environment (default: see postconf -d output) | in_flow_delay (default: 1s) | inet_interfaces (default: all) | inet_protocols (default: see 'postconf -d output') | info_log_address_format (default: external) | initial_destination_concurrency (default: 5) | internal_mail_filter_classes (default: empty) | invalid_hostname_reject_code (default: 501) | ipc_idle (default: version dependent) | ipc_timeout (default: 3600s) | ipc_ttl (default: 1000s) | known_tcp_ports (default: lmtp=24, smtp=25, smtps=submissions=465, submis- | line_length_limit (default: 2048) | lmdb_map_size (default: 16777216) | lmtp_address_preference (default: ipv6) | lmtp_address_verify_target (default: rcpt) | lmtp_assume_final (default: no) | lmtp_balance_inet_protocols (default: yes) | lmtp_bind_address (default: empty) | lmtp_bind_address6 (default: empty) | lmtp_bind_address_enforce (default: empty) | lmtp_body_checks (default: empty) | lmtp_cache_connection (default: yes) | lmtp_cname_overrides_servername (default: yes) | lmtp_connect_timeout (default: 0s) | lmtp_connection_cache_destinations (default: empty) | lmtp_connection_cache_on_demand (default: yes) | lmtp_connection_cache_time_limit (default: 2s) | lmtp_connection_reuse_count_limit (default: 0) | lmtp_connection_reuse_time_limit (default: 300s) | lmtp_data_done_timeout (default: 600s) | lmtp_data_init_timeout (default: 120s) | lmtp_data_xfer_timeout (default: 180s) | lmtp_defer_if_no_mx_address_found (default: no) | lmtp_delivery_status_filter (default: empty) | lmtp_destination_concurrency_limit (default: $default_destination_concur- | lmtp_destination_recipient_limit (default: $default_destination_recipi- | lmtp_discard_lhlo_keyword_address_maps (default: empty) | lmtp_discard_lhlo_keywords (default: empty) | lmtp_dns_reply_filter (default: empty) | lmtp_dns_resolver_options (default: empty) | lmtp_dns_support_level (default: empty) | lmtp_enforce_tls (default: no) | lmtp_fallback_relay (default: empty) | lmtp_generic_maps (default: empty) | lmtp_header_checks (default: empty) | lmtp_host_lookup (default: dns) | lmtp_lhlo_name (default: $myhostname) | lmtp_lhlo_timeout (default: 300s) | lmtp_line_length_limit (default: 990) | lmtp_mail_timeout (default: 300s) | lmtp_mime_header_checks (default: empty) | lmtp_min_data_rate (default: 500) | lmtp_mx_address_limit (default: 5) | lmtp_mx_session_limit (default: 2) | lmtp_nested_header_checks (default: empty) | lmtp_per_record_deadline (default: no) | lmtp_per_request_deadline (default: no) | lmtp_pix_workaround_delay_time (default: 10s) | lmtp_pix_workaround_maps (default: empty) | lmtp_pix_workaround_threshold_time (default: 500s) | lmtp_pix_workarounds (default: empty) | lmtp_quit_timeout (default: 300s) | lmtp_quote_rfc821_envelope (default: yes) | lmtp_randomize_addresses (default: yes) | lmtp_rcpt_timeout (default: 300s) | lmtp_reply_filter (default: empty) | lmtp_rset_timeout (default: 20s) | lmtp_sasl_auth_cache_name (default: empty) | lmtp_sasl_auth_cache_time (default: 90d) | lmtp_sasl_auth_enable (default: no) | lmtp_sasl_auth_soft_bounce (default: yes) | lmtp_sasl_mechanism_filter (default: empty) | lmtp_sasl_password_maps (default: empty) | lmtp_sasl_path (default: empty) | lmtp_sasl_security_options (default: noplaintext, noanonymous) | lmtp_sasl_tls_security_options (default: $lmtp_sasl_security_options) | lmtp_sasl_tls_verified_security_options (default: $lmtp_sasl_tls_security_op- | lmtp_sasl_type (default: cyrus) | lmtp_send_dummy_mail_auth (default: no) | lmtp_send_xforward_command (default: no) | lmtp_sender_dependent_authentication (default: no) | lmtp_skip_5xx_greeting (default: yes) | lmtp_skip_quit_response (default: no) | lmtp_starttls_timeout (default: 300s) | lmtp_tcp_port (default: 24) | lmtp_tls_CAfile (default: empty) | lmtp_tls_CApath (default: empty) | lmtp_tls_block_early_mail_reply (default: empty) | lmtp_tls_cert_file (default: empty) | lmtp_tls_chain_files (default: empty) | lmtp_tls_ciphers (default: medium) | lmtp_tls_connection_reuse (default: no) | lmtp_tls_dcert_file (default: empty) | lmtp_tls_dkey_file (default: $lmtp_tls_dcert_file) | lmtp_tls_eccert_file (default: empty) | lmtp_tls_eckey_file (default: empty) | lmtp_tls_enforce_peername (default: yes) | lmtp_tls_exclude_ciphers (default: empty) | lmtp_tls_fingerprint_cert_match (default: empty) | lmtp_tls_fingerprint_digest (default: see postconf -d output) | lmtp_tls_force_insecure_host_tlsa_lookup (default: no) | lmtp_tls_key_file (default: $lmtp_tls_cert_file) | lmtp_tls_loglevel (default: 0) | lmtp_tls_mandatory_ciphers (default: medium) | lmtp_tls_mandatory_exclude_ciphers (default: empty) | lmtp_tls_mandatory_protocols (default: see postconf -d output) | lmtp_tls_note_starttls_offer (default: no) | lmtp_tls_per_site (default: empty) | lmtp_tls_policy_maps (default: empty) | lmtp_tls_protocols (default: see postconf -d output) | lmtp_tls_scert_verifydepth (default: 9) | lmtp_tls_secure_cert_match (default: nexthop) | lmtp_tls_security_level (default: empty) | lmtp_tls_servername (default: empty) | lmtp_tls_session_cache_database (default: empty) | lmtp_tls_session_cache_timeout (default: 3600s) | lmtp_tls_trust_anchor_file (default: empty) | lmtp_tls_verify_cert_match (default: hostname) | lmtp_tls_wrappermode (default: no) | lmtp_use_tls (default: no) | lmtp_xforward_timeout (default: 300s) | local_command_shell (default: empty) | local_delivery_status_filter (default: $default_delivery_status_filter) | local_destination_concurrency_limit (default: 2) | local_destination_recipient_limit (default: 1) | local_header_rewrite_clients (default: permit_inet_interfaces) | local_login_sender_maps (default: static:*) | local_recipient_maps (default: proxy:unix:passwd.byname $alias_maps) | local_transport (default: local:$myhostname) | luser_relay (default: empty) | mail_name (default: Postfix) | mail_owner (default: postfix) | mail_release_date (default: see postconf -d output) | mail_spool_directory (default: see postconf -d output) | mail_version (default: see postconf -d output) | mailbox_command (default: empty) | mailbox_command_maps (default: empty) | mailbox_delivery_lock (default: see postconf -d output) | mailbox_size_limit (default: 51200000) | mailbox_transport (default: empty) | mailbox_transport_maps (default: empty) | maillog_file (default: empty) | maillog_file_compressor (default: gzip) | maillog_file_prefixes (default: /var, /dev/stdout) | maillog_file_rotate_suffix (default: %Y%m%d-%H%M%S) | mailq_path (default: see postconf -d output) | manpage_directory (default: see postconf -d output) | maps_rbl_domains (default: empty) | maps_rbl_reject_code (default: 554) | masquerade_classes (default: envelope_sender, header_sender, header_recipient) | masquerade_domains (default: empty) | masquerade_exceptions (default: empty) | master_service_disable (default: empty) | max_idle (default: 100s) | max_use (default: 100) | maximal_backoff_time (default: 4000s) | maximal_queue_lifetime (default: 5d) | message_drop_headers (default: bcc, content-length, resent-bcc, return-path) | message_reject_characters (default: empty) | message_size_limit (default: 10240000) | message_strip_characters (default: empty) | meta_directory (default: see 'postconf -d' output) | milter_command_timeout (default: 30s) | milter_connect_macros (default: see postconf -d output) | milter_connect_timeout (default: 30s) | milter_content_timeout (default: 300s) | milter_data_macros (default: see postconf -d output) | milter_default_action (default: tempfail) | milter_end_of_data_macros (default: see postconf -d output) | milter_end_of_header_macros (default: see postconf -d output) | milter_header_checks (default: empty) | milter_helo_macros (default: see postconf -d output) | milter_macro_daemon_name (default: $myhostname) | milter_macro_defaults (default: empty) | milter_macro_v (default: $mail_name $mail_version) | milter_mail_macros (default: see postconf -d output) | milter_protocol (default: 6) | milter_rcpt_macros (default: see postconf -d output) | milter_unknown_command_macros (default: see postconf -d output) | mime_boundary_length_limit (default: 2048) | mime_header_checks (default: $header_checks) | mime_nesting_limit (default: 100) | minimal_backoff_time (default: 300s) | multi_instance_directories (default: empty) | multi_instance_enable (default: no) | multi_instance_group (default: empty) | multi_instance_name (default: empty) | multi_instance_wrapper (default: empty) | multi_recipient_bounce_reject_code (default: 550) | mydestination (default: $myhostname, localhost.$mydomain, localhost) | mydomain (default: see postconf -d output) | myhostname (default: see postconf -d output) | mynetworks (default: see postconf -d output) | mynetworks_style (default: Postfix >= 3.0: host, Postfix < 3.0: subnet) | myorigin (default: $myhostname) | nested_header_checks (default: $header_checks) | newaliases_path (default: see postconf -d output) | non_fqdn_reject_code (default: 504) | non_smtpd_milters (default: empty) | notify_classes (default: resource, software) | openssl_path (default: openssl) | owner_request_special (default: yes) | parent_domain_matches_subdomains (default: see postconf -d output) | permit_mx_backup_networks (default: empty) | pickup_service_name (default: pickup) | pipe_delivery_status_filter (default: $default_delivery_status_filter) | plaintext_reject_code (default: 450) | postlog_service_name (default: postlog) | postlogd_watchdog_timeout (default: 10s) | postmulti_control_commands (default: reload flush) | postmulti_start_commands (default: start) | postmulti_stop_commands (default: see postconf -d output) | postscreen_access_list (default: permit_mynetworks) | postscreen_allowlist_interfaces (default: static:all) | postscreen_bare_newline_action (default: ignore) | postscreen_bare_newline_enable (default: no) | postscreen_bare_newline_ttl (default: 30d) | postscreen_blacklist_action (default: ignore) | postscreen_cache_cleanup_interval (default: 12h) | postscreen_cache_map (default: btree:$data_directory/postscreen_cache) | postscreen_cache_retention_time (default: 7d) | postscreen_client_connection_count_limit (default: $smtpd_client_connec- | postscreen_command_count_limit (default: 20) | postscreen_command_filter (default: $smtpd_command_filter) | postscreen_command_time_limit (default: normal: 300s, overload: 10s) | postscreen_denylist_action (default: ignore) | postscreen_disable_vrfy_command (default: $disable_vrfy_command) | postscreen_discard_ehlo_keyword_address_maps (default: $smtpd_dis- | postscreen_discard_ehlo_keywords (default: $smtpd_discard_ehlo_keywords) | postscreen_dnsbl_action (default: ignore) | postscreen_dnsbl_allowlist_threshold (default: 0) | postscreen_dnsbl_max_ttl (default: | postscreen_dnsbl_min_ttl (default: 60s) | postscreen_dnsbl_reply_map (default: empty) | postscreen_dnsbl_sites (default: empty) | postscreen_dnsbl_threshold (default: 1) | postscreen_dnsbl_timeout (default: 10s) | postscreen_dnsbl_ttl (default: 1h) | postscreen_dnsbl_whitelist_threshold (default: 0) | postscreen_enforce_tls (default: $smtpd_enforce_tls) | postscreen_expansion_filter (default: see postconf -d output) | postscreen_forbidden_commands (default: $smtpd_forbidden_commands) | postscreen_greet_action (default: ignore) | postscreen_greet_banner (default: $smtpd_banner) | postscreen_greet_ttl (default: 1d) | postscreen_greet_wait (default: normal: 6s, overload: 2s) | postscreen_helo_required (default: $smtpd_helo_required) | postscreen_non_smtp_command_action (default: drop) | postscreen_non_smtp_command_enable (default: no) | postscreen_non_smtp_command_ttl (default: 30d) | postscreen_pipelining_action (default: enforce) | postscreen_pipelining_enable (default: no) | postscreen_pipelining_ttl (default: 30d) | postscreen_post_queue_limit (default: $default_process_limit) | postscreen_pre_queue_limit (default: $default_process_limit) | postscreen_reject_footer (default: $smtpd_reject_footer) | postscreen_reject_footer_maps (default: $smtpd_reject_footer_maps) | postscreen_tls_security_level (default: $smtpd_tls_security_level) | postscreen_upstream_proxy_protocol (default: empty) | postscreen_upstream_proxy_timeout (default: 5s) | postscreen_use_tls (default: $smtpd_use_tls) | postscreen_watchdog_timeout (default: 10s) | postscreen_whitelist_interfaces (default: static:all) | prepend_delivered_header (default: command, file, forward) | process_id (read-only) | process_id_directory (default: pid) | process_name (read-only) | propagate_unmatched_extensions (default: canonical, virtual) | proxy_interfaces (default: empty) | proxy_read_maps (default: see postconf -d output) | proxy_write_maps (default: see postconf -d output) | proxymap_service_name (default: proxymap) | proxywrite_service_name (default: proxywrite) | qmgr_clog_warn_time (default: 300s) | qmgr_daemon_timeout (default: 1000s) | qmgr_fudge_factor (default: 100) | qmgr_ipc_timeout (default: 60s) | qmgr_message_active_limit (default: 20000) | qmgr_message_recipient_limit (default: 20000) | qmgr_message_recipient_minimum (default: 10) | qmqpd_authorized_clients (default: empty) | qmqpd_client_port_logging (default: no) | qmqpd_error_delay (default: 1s) | qmqpd_timeout (default: 300s) | queue_directory (default: see postconf -d output) | queue_file_attribute_count_limit (default: 100) | queue_minfree (default: 0) | queue_run_delay (default: 300s) | queue_service_name (default: qmgr) | rbl_reply_maps (default: empty) | readme_directory (default: see postconf -d output) | receive_override_options (default: empty) | recipient_bcc_maps (default: empty) | recipient_canonical_classes (default: envelope_recipient, header_recipient) | recipient_canonical_maps (default: empty) | recipient_delimiter (default: empty) | reject_code (default: 554) | reject_tempfail_action (default: defer_if_permit) | relay_clientcerts (default: empty) | relay_destination_concurrency_limit (default: $default_destination_concur- | relay_destination_recipient_limit (default: $default_destination_recipi- | relay_domains (default: Postfix >= 3.0: empty, Postfix < 3.0: $mydestination) | relay_domains_reject_code (default: 554) | relay_recipient_maps (default: empty) | relay_transport (default: relay) | relayhost (default: empty) | relocated_maps (default: empty) | remote_header_rewrite_domain (default: empty) | require_home_directory (default: no) | reset_owner_alias (default: no) | resolve_dequoted_address (default: yes) | resolve_null_domain (default: no) | resolve_numeric_domain (default: no) | respectful_logging (default: see 'postconf -d' output) | rewrite_service_name (default: rewrite) | sample_directory (default: /usr/local/etc/postfix) | send_cyrus_sasl_authzid (default: no) | sender_based_routing (default: no) | sender_bcc_maps (default: empty) | sender_canonical_classes (default: envelope_sender, header_sender) | sender_canonical_maps (default: empty) | sender_dependent_default_transport_maps (default: empty) | sender_dependent_relayhost_maps (default: empty) | sendmail_fix_line_endings (default: always) | sendmail_path (default: see postconf -d output) | service_name (read-only) | service_throttle_time (default: 60s) | setgid_group (default: postdrop) | shlib_directory (default: see 'postconf -d' output) | show_user_unknown_table_name (default: yes) | showq_service_name (default: showq) | smtp_address_preference (default: any) | smtp_address_verify_target (default: rcpt) | smtp_always_send_ehlo (default: yes) | smtp_balance_inet_protocols (default: yes) | smtp_bind_address (default: empty) | smtp_bind_address6 (default: empty) | smtp_bind_address_enforce (default: no) | smtp_body_checks (default: empty) | smtp_cname_overrides_servername (default: version dependent) | smtp_connect_timeout (default: 30s) | smtp_connection_cache_destinations (default: empty) | smtp_connection_cache_on_demand (default: yes) | smtp_connection_cache_time_limit (default: 2s) | smtp_connection_reuse_count_limit (default: 0) | smtp_connection_reuse_time_limit (default: 300s) | smtp_data_done_timeout (default: 600s) | smtp_data_init_timeout (default: 120s) | smtp_data_xfer_timeout (default: 180s) | smtp_defer_if_no_mx_address_found (default: no) | smtp_delivery_status_filter (default: $default_delivery_status_filter) | smtp_destination_concurrency_limit (default: $default_destination_concur- | smtp_destination_recipient_limit (default: $default_destination_recipi- | smtp_discard_ehlo_keyword_address_maps (default: empty) | smtp_discard_ehlo_keywords (default: empty) | smtp_dns_reply_filter (default: empty) | smtp_dns_resolver_options (default: empty) | smtp_dns_support_level (default: empty) | smtp_enforce_tls (default: no) | smtp_fallback_relay (default: $fallback_relay) | smtp_generic_maps (default: empty) | smtp_header_checks (default: empty) | smtp_helo_name (default: $myhostname) | smtp_helo_timeout (default: 300s) | smtp_host_lookup (default: dns) | smtp_line_length_limit (default: 998) | smtp_mail_timeout (default: 300s) | smtp_mime_header_checks (default: empty) | smtp_min_data_rate (default: 500) | smtp_mx_address_limit (default: 5) | smtp_mx_session_limit (default: 2) | smtp_nested_header_checks (default: empty) | smtp_never_send_ehlo (default: no) | smtp_per_record_deadline (default: no) | smtp_per_request_deadline (default: no) | smtp_pix_workaround_delay_time (default: 10s) | smtp_pix_workaround_maps (default: empty) | smtp_pix_workaround_threshold_time (default: 500s) | smtp_pix_workarounds (default: disable_esmtp, delay_dotcrlf) | smtp_quit_timeout (default: 300s) | smtp_quote_rfc821_envelope (default: yes) | smtp_randomize_addresses (default: yes) | smtp_rcpt_timeout (default: 300s) | smtp_reply_filter (default: empty) | smtp_rset_timeout (default: 20s) | smtp_sasl_auth_cache_name (default: empty) | smtp_sasl_auth_cache_time (default: 90d) | smtp_sasl_auth_enable (default: no) | smtp_sasl_auth_soft_bounce (default: yes) | smtp_sasl_mechanism_filter (default: empty) | smtp_sasl_password_maps (default: empty) | smtp_sasl_path (default: empty) | smtp_sasl_security_options (default: noplaintext, noanonymous) | smtp_sasl_tls_security_options (default: $smtp_sasl_security_options) | smtp_sasl_tls_verified_security_options (default: $smtp_sasl_tls_security_op- | smtp_sasl_type (default: cyrus) | smtp_send_dummy_mail_auth (default: no) | smtp_send_xforward_command (default: no) | smtp_sender_dependent_authentication (default: no) | smtp_skip_4xx_greeting (default: yes) | smtp_skip_5xx_greeting (default: yes) | smtp_skip_quit_response (default: yes) | smtp_starttls_timeout (default: 300s) | smtp_tcp_port (default: smtp) | smtp_tls_CAfile (default: empty) | smtp_tls_CApath (default: empty) | smtp_tls_block_early_mail_reply (default: no) | smtp_tls_cert_file (default: empty) | smtp_tls_chain_files (default: empty) | smtp_tls_cipherlist (default: empty) | smtp_tls_ciphers (default: medium) | smtp_tls_connection_reuse (default: no) | smtp_tls_dane_insecure_mx_policy (default: see postconf -d output) | smtp_tls_dcert_file (default: empty) | smtp_tls_dkey_file (default: $smtp_tls_dcert_file) | smtp_tls_eccert_file (default: empty) | smtp_tls_eckey_file (default: $smtp_tls_eccert_file) | smtp_tls_enforce_peername (default: yes) | smtp_tls_exclude_ciphers (default: empty) | smtp_tls_fingerprint_cert_match (default: empty) | smtp_tls_fingerprint_digest (default: see postconf -d output) | smtp_tls_force_insecure_host_tlsa_lookup (default: no) | smtp_tls_key_file (default: $smtp_tls_cert_file) | smtp_tls_loglevel (default: 0) | smtp_tls_mandatory_ciphers (default: medium) | smtp_tls_mandatory_exclude_ciphers (default: empty) | smtp_tls_mandatory_protocols (default: see postconf -d output) | smtp_tls_note_starttls_offer (default: no) | smtp_tls_per_site (default: empty) | smtp_tls_policy_maps (default: empty) | smtp_tls_protocols (default: see postconf -d output) | smtp_tls_scert_verifydepth (default: 9) | smtp_tls_secure_cert_match (default: nexthop, dot-nexthop) | smtp_tls_security_level (default: empty) | smtp_tls_servername (default: empty) | smtp_tls_session_cache_database (default: empty) | smtp_tls_session_cache_timeout (default: 3600s) | smtp_tls_trust_anchor_file (default: empty) | smtp_tls_verify_cert_match (default: hostname) | smtp_tls_wrappermode (default: no) | smtp_use_tls (default: no) | smtp_xforward_timeout (default: 300s) | smtpd_authorized_verp_clients (default: $authorized_verp_clients) | smtpd_authorized_xclient_hosts (default: empty) | smtpd_authorized_xforward_hosts (default: empty) | smtpd_banner (default: $myhostname ESMTP $mail_name) | smtpd_client_auth_rate_limit (default: 0) | smtpd_client_connection_count_limit (default: 50) | smtpd_client_connection_rate_limit (default: 0) | smtpd_client_event_limit_exceptions (default: $mynetworks) | smtpd_client_message_rate_limit (default: 0) | smtpd_client_new_tls_session_rate_limit (default: 0) | smtpd_client_port_logging (default: no) | smtpd_client_recipient_rate_limit (default: 0) | smtpd_client_restrictions (default: empty) | smtpd_command_filter (default: empty) | smtpd_data_restrictions (default: empty) | smtpd_delay_open_until_valid_rcpt (default: yes) | smtpd_delay_reject (default: yes) | smtpd_discard_ehlo_keyword_address_maps (default: empty) | smtpd_discard_ehlo_keywords (default: empty) | smtpd_dns_reply_filter (default: empty) | smtpd_end_of_data_restrictions (default: empty) | smtpd_enforce_tls (default: no) | smtpd_error_sleep_time (default: 1s) | smtpd_etrn_restrictions (default: empty) | smtpd_expansion_filter (default: see postconf -d output) | smtpd_forbidden_commands (default: CONNECT GET POST regexp:{{/^[^A-Z]/ Bo- | smtpd_hard_error_limit (default: normal: 20, overload: 1) | smtpd_helo_required (default: no) | smtpd_helo_restrictions (default: empty) | smtpd_history_flush_threshold (default: 100) | smtpd_junk_command_limit (default: normal: 100, overload: 1) | smtpd_log_access_permit_actions (default: empty) | smtpd_milter_maps (default: empty) | smtpd_milters (default: empty) | smtpd_min_data_rate (default: 500) | smtpd_noop_commands (default: empty) | smtpd_null_access_lookup_key (default: <>) | smtpd_peername_lookup (default: yes) | smtpd_per_record_deadline (default: normal: no, overload: yes) | smtpd_per_request_deadline (default: normal: no, overload: yes) | smtpd_policy_service_default_action (default: 451 4.3.5 Server configuration | smtpd_policy_service_max_idle (default: 300s) | smtpd_policy_service_max_ttl (default: 1000s) | smtpd_policy_service_policy_context (default: empty) | smtpd_policy_service_request_limit (default: 0) | smtpd_policy_service_retry_delay (default: 1s) | smtpd_policy_service_timeout (default: 100s) | smtpd_policy_service_try_limit (default: 2) | smtpd_proxy_ehlo (default: $myhostname) | smtpd_proxy_filter (default: empty) | smtpd_proxy_options (default: empty) | smtpd_proxy_timeout (default: 100s) | smtpd_recipient_limit (default: 1000) | smtpd_recipient_overshoot_limit (default: 1000) | smtpd_recipient_restrictions (default: see postconf -d output) | smtpd_reject_footer (default: empty) | smtpd_reject_footer_maps (default: empty) | smtpd_reject_unlisted_recipient (default: yes) | smtpd_reject_unlisted_sender (default: no) | smtpd_relay_before_recipient_restrictions (default: see postconf -d output) | smtpd_relay_restrictions (default: permit_mynetworks, permit_sasl_authenti- | smtpd_restriction_classes (default: empty) | smtpd_sasl_application_name (default: smtpd) | smtpd_sasl_auth_enable (default: no) | smtpd_sasl_authenticated_header (default: no) | smtpd_sasl_exceptions_networks (default: empty) | smtpd_sasl_local_domain (default: empty) | smtpd_sasl_mechanism_filter (default: !external, static:rest) | smtpd_sasl_path (default: smtpd) | smtpd_sasl_response_limit (default: 12288) | smtpd_sasl_security_options (default: noanonymous) | smtpd_sasl_service (default: smtp) | smtpd_sasl_tls_security_options (default: $smtpd_sasl_security_options) | smtpd_sasl_type (default: cyrus) | smtpd_sender_login_maps (default: empty) | smtpd_sender_restrictions (default: empty) | smtpd_service_name (default: smtpd) | smtpd_soft_error_limit (default: 10) | smtpd_starttls_timeout (default: see postconf -d output) | smtpd_timeout (default: normal: 300s, overload: 10s) | smtpd_tls_CAfile (default: empty) | smtpd_tls_CApath (default: empty) | smtpd_tls_always_issue_session_ids (default: yes) | smtpd_tls_ask_ccert (default: no) | smtpd_tls_auth_only (default: no) | smtpd_tls_ccert_verifydepth (default: 9) | smtpd_tls_cert_file (default: empty) | smtpd_tls_chain_files (default: empty) | smtpd_tls_cipherlist (default: empty) | smtpd_tls_ciphers (default: medium) | smtpd_tls_dcert_file (default: empty) | smtpd_tls_dh1024_param_file (default: empty) | smtpd_tls_dh512_param_file (default: empty) | smtpd_tls_dkey_file (default: $smtpd_tls_dcert_file) | smtpd_tls_eccert_file (default: empty) | smtpd_tls_eckey_file (default: $smtpd_tls_eccert_file) | smtpd_tls_eecdh_grade (default: see postconf -d output) | smtpd_tls_exclude_ciphers (default: empty) | smtpd_tls_fingerprint_digest (default: see postconf -d output) | smtpd_tls_key_file (default: $smtpd_tls_cert_file) | smtpd_tls_loglevel (default: 0) | smtpd_tls_mandatory_ciphers (default: medium) | smtpd_tls_mandatory_exclude_ciphers (default: empty) | smtpd_tls_mandatory_protocols (default: see postconf -d output) | smtpd_tls_protocols (default: see postconf -d output) | smtpd_tls_received_header (default: no) | smtpd_tls_req_ccert (default: no) | smtpd_tls_security_level (default: empty) | smtpd_tls_session_cache_database (default: empty) | smtpd_tls_session_cache_timeout (default: 3600s) | smtpd_tls_wrappermode (default: no) | smtpd_upstream_proxy_protocol (default: empty) | smtpd_upstream_proxy_timeout (default: 5s) | smtpd_use_tls (default: no) | smtputf8_autodetect_classes (default: sendmail, verify) | smtputf8_enable (default: yes) | soft_bounce (default: no) | stale_lock_time (default: 500s) | stress (default: empty) | strict_7bit_headers (default: no) | strict_8bitmime (default: no) | strict_8bitmime_body (default: no) | strict_mailbox_ownership (default: yes) | strict_mime_encoding_domain (default: no) | strict_rfc821_envelopes (default: no) | strict_smtputf8 (default: no) | sun_mailtool_compatibility (default: no) | swap_bangpath (default: yes) | syslog_facility (default: mail) | syslog_name (default: see postconf -d output) | tcp_windowsize (default: 0) | tls_append_default_CA (default: no) | tls_daemon_random_bytes (default: 32) | tls_dane_digest_agility (default: on) | tls_dane_digests (default: sha512 sha256) | tls_dane_trust_anchor_digest_enable (default: yes) | tls_disable_workarounds (default: see postconf -d output) | tls_eecdh_auto_curves (default: see postconf -d output) | tls_eecdh_strong_curve (default: prime256v1) | tls_eecdh_ultra_curve (default: secp384r1) | tls_export_cipherlist (default: see postconf -d output) | tls_fast_shutdown_enable (default: yes) | tls_high_cipherlist (default: see postconf -d output) | tls_legacy_public_key_fingerprints (default: no) | tls_low_cipherlist (default: see postconf -d output) | tls_medium_cipherlist (default: see postconf -d output) | tls_null_cipherlist (default: eNULL:!aNULL) | tls_preempt_cipherlist (default: no) | tls_random_bytes (default: 32) | tls_random_exchange_name (default: see postconf -d output) | tls_random_prng_update_period (default: 3600s) | tls_random_reseed_period (default: 3600s) | tls_random_source (default: see postconf -d output) | tls_server_sni_maps (default: empty) | tls_ssl_options (default: empty) | tls_wildcard_matches_multiple_labels (default: yes) | tlsmgr_service_name (default: tlsmgr) | tlsproxy_client_CAfile (default: $smtp_tls_CAfile) | tlsproxy_client_CApath (default: $smtp_tls_CApath) | tlsproxy_client_cert_file (default: $smtp_tls_cert_file) | tlsproxy_client_chain_files (default: $smtp_tls_chain_files) | tlsproxy_client_dcert_file (default: $smtp_tls_dcert_file) | tlsproxy_client_dkey_file (default: $smtp_tls_dkey_file) | tlsproxy_client_eccert_file (default: $smtp_tls_eccert_file) | tlsproxy_client_eckey_file (default: $smtp_tls_eckey_file) | tlsproxy_client_enforce_tls (default: $smtp_enforce_tls) | tlsproxy_client_fingerprint_digest (default: $smtp_tls_fingerprint_digest) | tlsproxy_client_key_file (default: $smtp_tls_key_file) | tlsproxy_client_level (default: $smtp_tls_security_level) | tlsproxy_client_loglevel (default: $smtp_tls_loglevel) | tlsproxy_client_loglevel_parameter (default: smtp_tls_loglevel) | tlsproxy_client_per_site (default: $smtp_tls_per_site) | tlsproxy_client_policy (default: $smtp_tls_policy_maps) | tlsproxy_client_policy_maps (default: $smtp_tls_policy_maps) | tlsproxy_client_scert_verifydepth (default: $smtp_tls_scert_verifydepth) | tlsproxy_client_security_level (default: $smtp_tls_security_level) | tlsproxy_client_use_tls (default: $smtp_use_tls) | tlsproxy_enforce_tls (default: $smtpd_enforce_tls) | tlsproxy_service_name (default: tlsproxy) | tlsproxy_tls_CAfile (default: $smtpd_tls_CAfile) | tlsproxy_tls_CApath (default: $smtpd_tls_CApath) | tlsproxy_tls_always_issue_session_ids (default: $smtpd_tls_always_issue_ses- | tlsproxy_tls_ask_ccert (default: $smtpd_tls_ask_ccert) | tlsproxy_tls_ccert_verifydepth (default: $smtpd_tls_ccert_verifydepth) | tlsproxy_tls_cert_file (default: $smtpd_tls_cert_file) | tlsproxy_tls_chain_files (default: $smtpd_tls_chain_files) | tlsproxy_tls_ciphers (default: $smtpd_tls_ciphers) | tlsproxy_tls_dcert_file (default: $smtpd_tls_dcert_file) | tlsproxy_tls_dh1024_param_file (default: $smtpd_tls_dh1024_param_file) | tlsproxy_tls_dh512_param_file (default: $smtpd_tls_dh512_param_file) | tlsproxy_tls_dkey_file (default: $smtpd_tls_dkey_file) | tlsproxy_tls_eccert_file (default: $smtpd_tls_eccert_file) | tlsproxy_tls_eckey_file (default: $smtpd_tls_eckey_file) | tlsproxy_tls_eecdh_grade (default: $smtpd_tls_eecdh_grade) | tlsproxy_tls_exclude_ciphers (default: $smtpd_tls_exclude_ciphers) | tlsproxy_tls_fingerprint_digest (default: $smtpd_tls_fingerprint_digest) | tlsproxy_tls_key_file (default: $smtpd_tls_key_file) | tlsproxy_tls_loglevel (default: $smtpd_tls_loglevel) | tlsproxy_tls_mandatory_ciphers (default: $smtpd_tls_mandatory_ciphers) | tlsproxy_tls_mandatory_exclude_ciphers (default: $smtpd_tls_mandatory_ex- | tlsproxy_tls_mandatory_protocols (default: $smtpd_tls_mandatory_protocols) | tlsproxy_tls_protocols (default: $smtpd_tls_protocols) | tlsproxy_tls_req_ccert (default: $smtpd_tls_req_ccert) | tlsproxy_tls_security_level (default: $smtpd_tls_security_level) | tlsproxy_tls_session_cache_timeout (default: $smtpd_tls_session_cache_timeout) | tlsproxy_use_tls (default: $smtpd_use_tls) | tlsproxy_watchdog_timeout (default: 10s) | trace_service_name (default: trace) | transport_delivery_slot_cost (default: $default_delivery_slot_cost) | transport_delivery_slot_discount (default: $default_delivery_slot_discount) | transport_delivery_slot_loan (default: $default_delivery_slot_loan) | transport_destination_concurrency_failed_cohort_limit (default: $default_des- | transport_destination_concurrency_limit (default: $default_destination_concur- | transport_destination_concurrency_negative_feedback (default: $default_desti- | transport_destination_concurrency_positive_feedback (default: $default_desti- | transport_destination_rate_delay (default: $default_destination_rate_delay) | transport_destination_recipient_limit (default: $default_destination_recipi- | transport_extra_recipient_limit (default: $default_extra_recipient_limit) | transport_initial_destination_concurrency (default: $initial_destination_con- | transport_maps (default: empty) | transport_minimum_delivery_slots (default: $default_minimum_delivery_slots) | transport_recipient_limit (default: $default_recipient_limit) | transport_recipient_refill_delay (default: $default_recipient_refill_delay) | transport_recipient_refill_limit (default: $default_recipient_refill_limit) | transport_retry_time (default: 60s) | transport_time_limit (default: $command_time_limit) | transport_transport_rate_delay (default: $default_transport_rate_delay) | trigger_timeout (default: 10s) | undisclosed_recipients_header (default: see postconf -d output) | unknown_address_reject_code (default: 450) | unknown_address_tempfail_action (default: $reject_tempfail_action) | unknown_client_reject_code (default: 450) | unknown_helo_hostname_tempfail_action (default: $reject_tempfail_action) | unknown_hostname_reject_code (default: 450) | unknown_local_recipient_reject_code (default: 550) | unknown_relay_recipient_reject_code (default: 550) | unknown_virtual_alias_reject_code (default: 550) | unknown_virtual_mailbox_reject_code (default: 550) | unverified_recipient_defer_code (default: 450) | unverified_recipient_reject_code (default: 450) | unverified_recipient_reject_reason (default: empty) | unverified_recipient_tempfail_action (default: $reject_tempfail_action) | unverified_sender_defer_code (default: 450) | unverified_sender_reject_code (default: 450) | unverified_sender_reject_reason (default: empty) | unverified_sender_tempfail_action (default: $reject_tempfail_action) | verp_delimiter_filter (default: -=+) | virtual_alias_address_length_limit (default: 1000) | virtual_alias_domains (default: $virtual_alias_maps) | virtual_alias_expansion_limit (default: 1000) | virtual_alias_maps (default: $virtual_maps) | virtual_alias_recursion_limit (default: 1000) | virtual_delivery_status_filter (default: $default_delivery_status_filter) | virtual_destination_concurrency_limit (default: $default_destination_concur- | virtual_destination_recipient_limit (default: $default_destination_recipi- | virtual_gid_maps (default: empty) | virtual_mailbox_base (default: empty) | virtual_mailbox_domains (default: $virtual_mailbox_maps) | virtual_mailbox_limit (default: 51200000) | virtual_mailbox_lock (default: see postconf -d output) | virtual_mailbox_maps (default: empty) | virtual_maps (default: empty) | virtual_minimum_uid (default: 100) | virtual_transport (default: virtual) | virtual_uid_maps (default: empty) | SEE ALSO | LICENSE | AUTHOR(S)

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