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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 "$name", "${name}"	or "$(name)"  are  re-
		     cursively replaced	by the value of	the named parameter.

	      o	     The  expression  "${name?value}"  expands to "value" when
		     "$name" is	non-empty. This	form is	supported with Postfix
		     version 2.2 and later.

	      o	     The  expression  "${name:value}"  expands to "value" when
		     "$name" is	empty. This form  is  supported	 with  Postfix
		     version 2.2 and later.

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

       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.

       Time units: s (seconds),	m (minutes), h (hours),	d (days), w (weeks).

       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.

       Time units: s (seconds),	m (minutes), h (hours),	d (days), w (weeks).

       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.

       Time units: s (seconds),	m (minutes), h (hours),	d (days), w (weeks).

       This feature is available in Postfix 2.1	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.

       Time units: s (seconds),	m (minutes), h (hours),	d (days), w (weeks).

       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.

       Time units: s (seconds),	m (minutes), h (hours),	d (days), w (weeks).

       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).

       Time units: s (seconds),	m (minutes), h (hours),	d (days), w (weeks).

       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 (an integral value plus an optional one-letter  suffix  that
       specifies  the  time unit).  Specify a value of at least	several	hours,
       to avoid	problems with senders that use greylisting.   Avoid  nice  TTL
       values,	to  make the result less predictable.  Time units are: s (sec-
       onds), m	(minutes), h (hours), d	(days),	w (weeks).

       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.

       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, or via the
       MAIL_CONFIG environment parameter.

       This list must be specified in the default Postfix configuration	direc-
       tory,  and is used by set-gid Postfix commands such as postqueue(1) and
       postdrop(1).

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.

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.

       Time units: s (seconds),	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.

       This feature is available in Postfix 2.2	and later.

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

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: 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.

       Time  units:  s (seconds), 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.

       Time units: s (seconds),	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,	for 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 inter-operability	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.

       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
       command.	 Failure to change directory causes the	 delivery  to  be  de-
       ferred.

       The  following $name expansions are done	on command_execution_directory
       before the directory is changed.	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_expan-
       sion_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}
	      Expands to value when $name is non-empty.

       ${name:value}
	      Expands to value when $name is empty.

       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.

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

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	 corresponding
       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.

       Time units: s (seconds),	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 remote client or	server
       matches a pattern in the	debug_peer_list	parameter.

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

       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  parent_do-
       main_matches_subdomains parameter.

       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 is the counter 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,
       their  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_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 per-destination recipient
       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	deliv-
       eries to	the same destination; 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 recipients 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
       external	 file  or command.  These rights are used when delivery	is re-
       quested from an aliases(5) file that is owned by	root, or when delivery
       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 is subject to exactly one level of $name substitution:

       $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 blacklisted 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	blacklisted.

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

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

       $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?text}
	      Expands to `text'	if $name is not	empty.

       ${name:text}
	      Expands to `text'	if $name is empty.

       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  recipients  refills.
       When not	all message recipients fit into	the memory at once, keep load-
       ing more	of them	at least once every this many seconds.	This  is  used
       to  make	 sure  the  recipients are refilled in timely manner even when
       $default_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 the 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.

       Example:

       default_transport = uucp:relayhostname

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  -V" command-line option. Specify 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
       names of	mail delivery transports names that appear in the first	 field
       of master.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	seconds; delay
       values  below the delay_logging_resolution_limit	are logged as "0", and
       small delay values are logged with at most two-digit precision.

       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.

       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.

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.

       Time units: s (seconds),	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

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 white/blacklist lookups.

       This feature is available in Postfix 2.8	and later.

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_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_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 X-Original-To message  header.  This  header  is
       needed for multi-recipient mailboxes.

       When  this  parameter is	set to yes, the	cleanup(8) daemon performs du-
       plicate elimination on distinct pairs of	(original recipient, rewritten
       recipient),  and	 generates  non-empty  original	 recipient  queue file
       records.

       When this parameter is set to no, the cleanup(8)	daemon performs	dupli-
       cate elimination	on the rewritten recipient address only, and generates
       empty original recipient	queue file records.

       This feature is available in Postfix 2.1	and later. With	 Postfix  ver-
       sion 2.0, support for the X-Original-To message header is always	turned
       on. Postfix versions before 2.0 have no support for  the	 X-Original-To
       message header.

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. The name=value form is supported	with  Postfix  version
       2.1 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.

       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.

       Time units: s (seconds),	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  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}
	      Expands to value when $name is non-empty.

       ${name:value}
	      Expands to value when $name is empty.

       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_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 parameters that a Postfix process will	import
       from a non-Postfix parent process. Examples of relevant parameters:

       TZ     Needed for sane time keeping on most System-V-ish	systems.

       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. The name=value	form is	supported with Postfix version
       2.1 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: all)
       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

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 transport-
       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  Postfix-
       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.

       Time  units:  s (seconds), 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.

       Time  units:  s (seconds), 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.

       Time  units:  s (seconds), 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.

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_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_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_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 a 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.

       Time  units:  s (seconds), 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.

       Time units: s (seconds),	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.

       Time units: s (seconds),	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.

       Time  units:  s (seconds), 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_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_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_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].

       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.

       Time  units:  s (seconds), 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_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_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.

       Time units: s (seconds),	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.

       Time units: s (seconds),	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.

       Time  units:  s (seconds), 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 attack.

       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 queuing LMTP server.  Before  you	change
       the value to yes, it is best to make sure that your content filter sup-
       ports 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.

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_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_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: md5)
       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: !SSLv2, !SSLv3)
       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: !SSLv2, !SSLv3)
       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_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_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.

       Time units: s (seconds),	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 command.
       By default, non-Postfix commands	are executed  directly;	 commands  are
       given to	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_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).

       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_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.

       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 following $name expansions are done on luser_relay:

       $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}
	      Expands to value when $name has a	non-empty value.

       ${name:value}
	      Expands to value when $name has an empty value.

       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  system-
       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.

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.

       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.

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

       This feature is available in Postfix 2.3	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 address matches $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.

       Time units: s (seconds),	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.

       Time  units:  s (seconds), 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.

       Time units: s (seconds),	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_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.

       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.

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 (seconds), 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 (seconds),	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 (seconds), 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) application is  unavail-
       able or mis-configured. 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 whitelisting.
       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_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.

       Time  units:  s (seconds), 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	param-
       eter 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: 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.

       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_style (default: 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" 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.  Don't do this with a  dialup  site  -  it	 would
	      cause  Postfix  to  "trust" your entire provider's network.  In-
	      stead, specify an	explicit mynetworks list by hand, as described
	      with the mynetworks configuration	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 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. The  de-
       fault  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

owner_request_special (default:	yes)
       Give  special  treatment	to owner-listname and listname-request address
       localparts: don't split such addresses when the recipient_delimiter  is
       set to "-".  This feature is useful for mailing lists.

parent_domain_matches_subdomains (default: see postconf	-d output)
       What  Postfix  features match subdomains	of "domain.tld"	automatically,
       instead of  requiring  an  explicit  ".domain.tld"  pattern.   This  is
       planned	backwards compatibility:  eventually, all Postfix features are
       expected	to require explicit ".domain.tld" style	patterns when you  re-
       ally want to match subdomains.

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.

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.

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.

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   white/blacklist   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
	      Whitelist	 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.

	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
	      Whitelist	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
	      Blacklist	the client  and	 terminate  the	 search.  Subject  the
	      client  to  the  action  configured  with	 the postscreen_black-
	      list_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
	   postscreen_blacklist_action = enforce

       /usr/local/etc/postfix/postscreen_access.cidr:
	   # Rules are evaluated in the	order as specified.
	   # Blacklist 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_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 some the	result from some other
	      test expires.  This option is useful for testing and  collecting
	      statistics 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 (seconds),
       m (minutes), h (hours), d (days), w (weeks).

       This feature is available in Postfix 2.8.

postscreen_blacklist_action (default: ignore)
       The action that postscreen(8) takes when	a remote SMTP client is	perma-
       nently  blacklisted 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 2.8.

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.

       Time units: s (seconds),	m (minutes), h (hours),	d (days), w (weeks).

       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
       whitelist  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.

       Time units: s (seconds),	m (minutes), h (hours),	d (days), w (weeks).

       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:	${stress?10}${stress:300}s)
       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_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_reply_map (default: empty)
       A  mapping  from	actual DNSBL domain name which includes	a secret pass-
       word, 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 white/blacklist 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 whitelisting.

       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_ttl (default: 1h)
       The amount of time that postscreen(8) will use the result from  a  suc-
       cessful	DNS blocklist test. During this	time, the client IP address is
       excluded	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  (seconds),
       m (minutes), h (hours), d (days), w (weeks).

       This feature is available in Postfix 2.8.

postscreen_dnsbl_whitelist_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_whitelist_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 2.11.

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 whitelist	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 (seconds),
       m (minutes), h (hours), d (days), w (weeks).

       This feature is available in Postfix 2.8.

postscreen_greet_wait (default:	${stress?2}${stress:6}s)
       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 (seconds),	m (minutes), h (hours),	d (days), w (weeks).

       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 some the result from  some	 other
	      test  expires.  This option is useful for	testing	and collecting
	      statistics 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  (seconds),
       m (minutes), h (hours), d (days), w (weeks).

       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 some the result from  some	 other
	      test  expires.  This option is useful for	testing	and collecting
	      statistics 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  (seconds),
       m (minutes), h (hours), d (days), w (weeks).

       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-whitelisted 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-whitelisted 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_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.

       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  (seconds),
       m (minutes), h (hours), d (days), w (weeks).

       This feature is available in Postfix 2.8.

postscreen_whitelist_interfaces	(default: static:all)
       A  list	of  local  postscreen(8)  server  IP  addresses	 where	a non-
       whitelisted remote SMTP client  can  obtain  postscreen(8)'s  temporary
       whitelist 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	whitelist  status on any local postscreen(8) server IP
       address.

       When postscreen(8) listens on both primary and backup MX	addresses, the
       postscreen_whitelist_interfaces parameter can be	configured to give the
       temporary whitelist status only when a client connects to a primary  MX
       address.	 Once  a  client  is whitelisted it can	talk to	a Postfix SMTP
       server on any address. Thus, clients that connect only to backup	MX ad-
       dresses	will  never  become  whitelisted, 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_whitelist_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 whitelist connections to the	backup IP address.
	   postscreen_whitelist_interfaces = !168.100.189.8, static:all

       This feature is available in Postfix 2.9	and later.

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.  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.

       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.

       Time units: s (seconds),	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.

       Time units: s (seconds),	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.

       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.

       Time units: s (seconds),	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.

       Time  units:  s (seconds), 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.

       Time units: s (seconds),	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.

       This feature is available in Postfix 2.1	and later.

       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.

       Specify the types and names of databases	to  use.   After  change,  run
       "postmap	/usr/local/etc/postfix/recipient_bcc".

       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:

       recipient_bcc_maps = hash:$config_directory/recipient_bcc

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 a user name from	its  extension
       (example:  user+foo), or	a .forward file	name from its extension	(exam-
       ple: .forward+foo).  Basically, the software tries user+foo  and	 .for-
       ward+foo	 before	 trying	user and .forward.  This implementation	recog-
       nizes one delimiter character and one extension per  email  address  or
       .forward	file name.

       When  the recipient_delimiter set contains multiple characters (Postfix
       2.11 and	later),	a user name or .forward	file name  is  separated  from
       its  extension by the first character that matches the recipient_delim-
       iter set.

       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).

       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.

       Note: Postfix 2.9.0-2.9.5 computed the public  key  fingerprint	incor-
       rectly.	To  use	 public-key  fingerprints, upgrade to Postfix 2.9.6 or
       later.

       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:	$mydestination)
       What destination	domains	(and subdomains	thereof) this system will  re-
       lay  mail  to.  Subdomain  matching  is	controlled with	the parent_do-
       main_matches_subdomains parameter. For details about how	the  relay_do-
       mains value is used, see	the description	of the permit_auth_destination
       and reject_unauth_destination 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.

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
       table lookup.

       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	of non-local mail; overrides non-local domains
       in recipient addresses. This information	is overruled with relay_trans-
       port,	sender_dependent_default_transport_maps,    default_transport,
       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, specify a domain  name,  hostname,	hostname:port,
       [hostname]:port,	 [hostaddress]	or [hostaddress]:port. The form	[host-
       name] turns off MX lookups.

       If you're connected via UUCP, see the UUCP_README file for  useful  in-
       formation.

       Examples:

       relayhost = $mydomain
       relayhost = [gateway.example.com]
       relayhost = uucphost
       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).

       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, 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 addresses
       from that child alias will be written to	a new queue file, and a	tempo-
       rary  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.  The local(8) delivery agent then	attempts to deliver local  ad-
       dresses as soon as they come out	of child alias expansion.  If delivery
       to any address from child alias expansion fails with a temporary	 error
       condition, the entire mailing list may be expanded repeatedly until the
       mail expires in the queue, resulting in multiple	deliveries of the same
       message 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.

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	 inter-operability  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.

       This feature is available in Postfix 2.1	and later.

       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.

       Specify the types and names of databases	to  use.   After  change,  run
       "postmap	/usr/local/etc/postfix/sender_bcc".

       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

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.

       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.

       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_throttle_time (default:	60s)
       How  long  the Postfix master(8)	waits before forking a server that ap-
       pears to	be malfunctioning.

       Time units: s (seconds),	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".

show_user_unknown_table_name (default: yes)
       Display the name	of the recipient  table	 in  the  "User	 unknown"  re-
       sponses.	  The  extra detail makes trouble shooting easier but also re-
       veals information that is nobody	elses 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.	 With Postfix 2.8 the  default
       is "ipv6".

       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_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_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

       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

       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_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).

       Time units: s (seconds),	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  numeric
	      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.

       Time units: s (seconds),	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_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.

       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_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 validated.

       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.

       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	EHLO or	HELO 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.

       Time units: s (seconds),	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.

       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.

       Time  units:  s (seconds), 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_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	and later. With	older  Postfix
       releases, the behavior is as if this parameter is set to	"no".

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	a too short time makes this workaround ineffective when	 send-
       ing large messages over slow network connections.

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.

       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.

       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.

       Time units: s (seconds),	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.

       Time  units:  s (seconds), 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 inter-operability 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.

       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 no 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.

       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 remote hostname or domain, or	sender address when sender-de-
       pendent 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.

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.

       This feature is available in Postfix 2.2	and later.

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.

       Specify	"smtp_tls_CAfile  =  /path/to/system_CA_file"  to use ONLY the
       system-supplied default certificate 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 certificate 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 certificate 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.

       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_dcert_file =
	   smtp_tls_dkey_file =
	   smtp_tls_eccert_file	=
	   smtp_tls_eckey_file =

       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".	Create
       the  client.pem	file  with  "cat  client_cert.pem  intermediate_CA.pem
       root_CA.pem > client.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 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/client.pem

       This feature is available in Postfix 2.2	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 inter-operability	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_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.

       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 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.

       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.

       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  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 dis-
       ables ciphers that use the MD5 digest algorithm or the (single) DES en-
       cryption	 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, certificate 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.

       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 = md5
	   smtp_tls_fingerprint_cert_match =
	       3D:95:34:51:24:66:33:B9:D2:40:99:C0:C1:17:0B:D1
	       EC:3B:2D:B0:5B:B1:FB:6D:20:A3:9D:72:F6:8D:12:35

       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 = md5

	   /usr/local/etc/postfix/tls_policy:
	       example.com fingerprint
		   match=3D:95:34:51:24:66:33:B9:D2:40:99:C0:C1:17:0B:D1
		   match=EC:3B:2D:B0:5B:B1:FB:6D:20:A3:9D:72:F6:8D:12:35

       This feature is available in Postfix 2.5	and later.

smtp_tls_fingerprint_digest (default: md5)
       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  md5; this is consistent with the backwards
       compatible setting of the digest	used to	verify client certificates  in
       the SMTP	server.

       The  best practice algorithm is now sha1. Recent	advances in hash func-
       tion cryptanalysis have led to md5 being	deprecated in favor  of	 sha1.
       However,	 as  long  as  there  are  no known "second pre-image" attacks
       against md5, its	use in this context can	still be considered 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. For now this	means just md5 or sha1.

       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 -sha1 -in	cert.pem
	   SHA1	Fingerprint=D4:6A:AB:19:24:79:F8:32: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. With OpenSSL 1.0.0 and	later, the "pkey" com-
       mand supports all key types. With OpenSSL 0.9.8 and  earlier,  the  key
       type  is	 always	 RSA  (nobody uses DSA,	and EC keys are	not fully sup-
       ported by 0.9.8), so the	"rsa" command is used.

	   # OpenSSL 1.0 with all certificates and SHA-1 fingerprints.
	   $ openssl x509 -in cert.pem -noout -pubkey |
	       openssl pkey -pubin -outform DER	|
	       openssl dgst -sha1 -c
	   (stdin)= 64:3f:1f:f6:e5:1e:d4:2a:56:8b:fc:09:1a:61:98:b5:bc:7c:60:58

	   # OpenSSL 0.9.8 with	RSA certificates and MD5 fingerprints.
	   $ openssl x509 -in cert.pem -noout -pubkey |
	       openssl rsa -pubin -outform DER |
	       openssl dgst -md5 -c
	   (stdin)= f4:62:60:f6:12:8f:d5:8d:28:4d:13:a7:db:b2:ff:50

       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.

       Note: Postfix 2.9.0-2.9.5 computed the public  key  fingerprint	incor-
       rectly.	To  use	 public-key  fingerprints, upgrade to Postfix 2.9.6 or
       later.

       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.

       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  hexadecimal	and  ASCII  dump  of  TLS  negotiation
	      process.

	      4	 Also  log hexadecimal and ASCII dump of complete transmission
	      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	to not 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  to  not  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	to not 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 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 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	to not 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: !SSLv2, !SSLv3)
       List of SSL/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_policy_maps) the only valid separator is colon. An empty
       value means allow all protocols.	The valid protocol names, (see	\fBfB-
       SSL_get_version(3)),  are  "SSLv2",  "SSLv3"  and  "TLSv1". The default
       value is	"!SSLv2, !SSLv3" for Postfix  releases	after  the  middle  of
       2015, "!SSLv2" for older	releases.

       With Postfix >= 2.5 the parameter syntax	was expanded to	support	proto-
       col  exclusions.	 One  can  explicitly  exclude	"SSLv2"	  by   setting
       "smtp_tls_mandatory_protocols  =	 !SSLv2".  To exclude both "SSLv2" and
       "SSLv3" set "smtp_tls_mandatory_protocols =  !SSLv2,  !SSLv3".  Listing
       the  protocols  to  include,  rather than protocols to exclude, is sup-
       ported, but not recommended. The	exclusion form	more  closely  matches
       the underlying OpenSSL interface	semantics.

       The range of protocols advertised by an SSL/TLS client must be contigu-
       ous.  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, !TLSv1
       also disables any protocols version  higher  than  TLSv1	 leaving  only
       "SSLv3" enabled.

       Note:  As of OpenSSL 1.0.1 two new protocols are	defined, "TLSv1.1" and
       "TLSv1.2". When Postfix <= 2.5  is  linked  against  OpenSSL  1.0.1  or
       later,  these,  or  any other new protocol versions, cannot be disabled
       except by also disabling	"TLSv1"	(typically leaving just	"SSLv3").  The
       latest  patch  levels of	Postfix	>= 2.6,	and all	versions of Postfix >=
       2.10 can	explicitly disable support for "TLSv1.1" or "TLSv1.2".

       At the dane and dane-only security levels, when usable TLSA records are
       obtained	 for  the remote SMTP server, the Postfix SMTP client is obli-
       gated to	include	the SNI	TLS extension in its SSL client	hello message.
       This  may help the remote SMTP server live up to	its promise to provide
       a certificate that matches its TLSA records.  Since TLS extensions  re-
       quire  TLS  1.0	or later, the Postfix SMTP client must disable "SSLv2"
       and "SSLv3" when	SNI is required.  If you use "dane" or "dane-only"  do
       not disable TLSv1, except perhaps via the policy	table for destinations
       which you are sure will support "TLSv1.1" or "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 >= 2.5:
       smtp_tls_mandatory_protocols = !SSLv2, !SSLv3
       # Legacy	syntax:
       smtp_tls_mandatory_protocols = TLSv1

       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
	      the 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
	      and 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_peer-
	      name 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.

       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)
	      override the "smtp_tls_ciphers", "smtp_tls_exclude_ciphers"  and
	      "smtp_tls_protocols"  configuration parameters. When opportunis-
	      tic TLS handshakes fail, Postfix retries the connection with TLS
	      disabled.	  This allows mail delivery to sites with non-interop-
	      erable TLS implementations.

       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, and the
	      optional "exclude" attribute  (Postfix  >=  2.6)	overrides  the
	      main.cf  smtp_tls_mandatory_exclude_ciphers  parameter.  In  the
	      policy table, multiple 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 6698 (DANE)	TLS authentication and DNSSEC  support
	      is available with	Postfix	2.11 and later.

       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
	      6698 (DANE) TLS authentication and DNSSEC	support	 is  available
	      with Postfix 2.11	and later.

       fingerprint
	      Certificate fingerprint verification. Available with Postfix 2.5
	      and later. At this security level, there are no trusted certifi-
	      cate  authorities. The certificate trust chain, expiration date,
	      ... are not checked. Instead, the	optional match	attribute,  or
	      else   the  main.cf  smtp_tls_fingerprint_cert_match  parameter,
	      lists the	certificate fingerprints or the	public key fingerprint
	      (Postfix 2.9 and later) of the valid server certificate. The di-
	      gest 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	attri-
	      bute,  or	 multiple  match  attributes  can be employed. The ":"
	      character	is not used as a delimiter as it occurs	 between  each
	      pair of fingerprint (hexadecimal)	digits.

       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.

       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 common server, the	policy
	      entries for additional domains specify matching  rules  for  the
	      primary  domain  certificate.  While  transport  table overrides
	      routing the secondary domains to the primary nexthop also	 allow
	      secure verification, they	risk delivery to the wrong destination
	      when domains change hands	or are re-assigned  to	new  gateways.
	      With  the	 "match" attribute approach, routing is	not perturbed,
	      and mail is deferred if verification of a	new MX host fails.

       Example:

       /usr/local/etc/postfix/main.cf:
	   smtp_tls_policy_maps	= hash:$config_directory/tls_policy
	   # Postfix 2.5 and later
	   smtp_tls_fingerprint_digest = md5

       /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=EC:3B:2D:B0:5B:B1:FB:6D:20:A3:9D:72:F6:8D:12:35
	       match=3D:95:34:51:24:66:33:B9:D2:40:99:C0:C1:17:0B:D1

       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 ta-
       ble can render the secure level vulnerable to DNS forgery. Do  not  use
       the hostname strategy for secure-channel	configurations in environments
       where DNS security is not assured.

       This feature is available in Postfix 2.3	and later.

smtp_tls_protocols (default: !SSLv2, !SSLv3)
       List of TLS protocols that the Postfix SMTP client will exclude or  in-
       clude  with opportunistic TLS encryption. The default value is "!SSLv2,
       !SSLv3" for Postfix releases after the middle  of  2015,	 "!SSLv2"  for
       older  releases.	 Before	Postfix	2.6, the Postfix SMTP client would use
       all protocols with opportunistic	TLS.

       In main.cf the values are separated by whitespace, commas or colons. In
       the policy table	(see smtp_tls_policy_maps) the only valid separator is
       colon. An empty value means allow all  protocols.  The  valid  protocol
       names, (see \fBfBSSL_get_version(3)), are "SSLv2", "SSLv3" and "TLSv1".

       The range of protocols advertised by an SSL/TLS client must be contigu-
       ous.  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, !TLSv1
       also disables any protocols version  higher  than  TLSv1	 leaving  only
       "SSLv3" enabled.

       Note:  As of OpenSSL 1.0.1 two new protocols are	defined, "TLSv1.1" and
       "TLSv1.2". The latest patch levels of Postfix >=	2.6, and all  versions
       of  Postfix  >=	2.10  can  explicitly disable support for "TLSv1.1" or
       "TLSv1.2"

       To include a protocol list its name, to exclude	it,  prefix  the  name
       with  a	"!"  character.	 To  exclude  SSLv2  for opportunistic TLS set
       "smtp_tls_protocols = !SSLv2". To exclude both "SSLv2" and "SSLv3"  set
       "smtp_tls_protocols = !SSLv2, !SSLv3". Explicitly listing the protocols
       to include, rather than protocols to exclude,  is  supported,  but  not
       recommended.   The  exclusion  form more	closely	matches	the underlying
       OpenSSL interface semantics.

       Example:
       # TLSv1 or better:
       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.

       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 inter-operability.	  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
	      6698) 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 6698 (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
	      6698 (DANE) TLS authentication is	available  with	 Postfix  2.11
	      and later.

       fingerprint
	      Certificate  fingerprint	verification.  At this security	level,
	      there are	no trusted certificate 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
       # Postfix >= 2.6:
       # Do not	tweak opportunistic ciphers or protocol	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 from "export" to "low" or	"medium").
       smtp_tls_ciphers	= export
       smtp_tls_protocols = !SSLv2, !SSLv3

       # Mandatory (high-grade)	TLS encryption.
       smtp_tls_security_level = encrypt
       smtp_tls_mandatory_ciphers = high

       # Mandatory TLS verification of hostname	or nexthop domain.
       smtp_tls_security_level = verify
       smtp_tls_mandatory_ciphers = high
       smtp_tls_verify_cert_match = hostname, nexthop, dot-nexthop

       # Secure	channel	TLS with exact nexthop name match.
       smtp_tls_security_level = secure
       smtp_tls_mandatory_protocols = TLSv1
       smtp_tls_mandatory_ciphers = high
       smtp_tls_secure_cert_match = 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 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 = !SSLv2, !SSLv3
       smtp_tls_mandatory_ciphers = high
       smtp_tls_fingerprint_cert_match =
	   3D:95:34:51:24:66:33:B9:D2:40:99:C0:C1:17:0B:D1
	   EC:3B:2D:B0:5B:B1:FB:6D:20:A3:9D:72:F6:8D:12:35

       This feature is available in Postfix 2.3	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
       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.

       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.

       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 certificates.
       Therefore, these	certificates also may be found "in the middle" of  the
       trust  chain presented by the remote SMTP server, and any untrusted is-
       suing 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-destina-
       tion basis via the "tafile" attribute of	the "verify" and "secure" lev-
       els in smtp_tls_policy_maps.

       The  underlying	mechanism is in	support	of RFC 6698 (DANE TLSA), which
       defines mechanisms for a	client to securely determine server  TLS  cer-
       tificates 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  the	server
	      certificate  must	 be example.com, upper and lower case distinc-
	      tions 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_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.

       Time  units:  s (seconds), 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, fetchmail-
       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_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.

       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
	      Use the remote SMTP client certificate fingerprint or the	public
	      key  fingerprint	(Postfix  2.9 and later) as lookup key for the
	      specified	access(5) database; with Postfix version 2.2, also re-
	      quire  that  the remote SMTP client certificate is verified suc-
	      cessfully.  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 is  available  with
	      Postfix version 2.2 and later.

       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_mx_access type:table
	      Search the specified access(5) database for the MX hosts for the
	      client  hostname,	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 blacklists.  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	black-
	      lists.  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	blacklists.  This feature is available
	      in Postfix 2.6 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.  Note: a result of "OK" is not  allowed  for	safety
	      reasons.	 Instead, use DUNNO in order to	exclude	specific hosts
	      from blacklists.	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 blacklists.  This feature is available	in Postfix 2.7
	      and later.

       check_sasl_access type:table
	      Use the remote SMTP client SASL user name	as lookup key for  the
	      specified	access(5) database. The	lookup key has the form	"user-
	      name@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
	      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 system-
	      supplied default CAs.  This feature is  available	 with  Postfix
	      version 2.2.

       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
	      is available with	Postfix	version	2.2.

       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 whitelist  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 whitelisting	is fragile, since  the	client
	      name  lookup  can	 fail  due  to temporary outages.  Client name
	      whitelisting should be used only to reduce  false	 positives  in
	      e.g.   DNS-based	blocklists, and	not for	making access rule ex-
	      ceptions.
	      For safety, permit_rhswl_client  is  silently  ignored  when  it
	      would  override  reject_unauth_destination.   The	 result	is DE-
	      FER_IF_REJECT when whitelist  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,  2)  the name->address mapping fails, or 3) the name->ad-
	      dress 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
	      blacklisting feature fails due to	 a  temporary  problem.	  This
	      feature 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 a whitelisting feature fails
	      due  to a	temporary problem.  This feature is available in Post-
	      fix 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
	      EHLO or HELO 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  inter-oper-
       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:]]+)'>(.*)/     RCPT TO:<$1>$2

	   # Append XVERP to MAIL FROM commands	to request VERP-style delivery.
	   # See VERP_README for more information on how to use	Postfix	VERP.
	   /^(MAIL FROM:<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+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
       table is	not searched by	hostname for robustness	reasons.

       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_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.

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.

       This parameter is not subjected to $parameter expansion.

       This feature is available in Postfix 2.0	and later.

smtpd_forbidden_commands (default: CONNECT, GET, POST)
       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.

       This feature is available in Postfix 2.2	and later.

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	exceeded. 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.

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_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.
	      Note 1: a	result of "OK" is not allowed for safety reasons.  In-
	      stead,  use DUNNO	in order to exclude specific hosts from	black-
	      lists.  Note 2: specify "smtpd_helo_required = yes" to fully en-
	      force  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	black-
	      lists.  Note 2: specify "smtpd_helo_required = yes" to fully en-
	      force 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 unknown_hostname_reject_code parameter specifies the numeri-
	      cal response code	for rejected requests (default:	450).
	      The  unknown_helo_hostname_tempfail_action  parameter  specifies
	      the  action  after a temporary DNS error (default: defer_if_per-
	      mit). 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_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_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 and later. With older Postfix
       releases, the behavior is as if this parameter is set to	"no".

smtpd_policy_service_max_idle (default:	300s)
       The time	after which an idle SMTPD policy service connection is closed.

       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.

       This feature is available in Postfix 2.1	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.

       This feature is available in Postfix 2.1	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:"  are specified,  the  local	 machine  is  assumed.
       Pathname	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.

       Time  units:  s (seconds), 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_mx_access type:table
	      Search the specified access(5) database for the MX hosts 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 blacklists.  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 blacklists.  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 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 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	primary	MX for
	      the  recipient  domain.  Exception: permit_mx_backup accepts the
	      address when it specifies	an authorized  destination  (see  per-
	      mit_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  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  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 A	or  MX
	      record or	2) a malformed MX record such as a record with a zero-
	      length MX	hostname (Postfix version 2.3 and later).
	      The unknown_address_reject_code parameter	specifies the  numeri-
	      cal response code	for rejected requests (default:	450).  The re-
	      sponse is	always 450 in case of a	temporary DNS error.
	      The unknown_address_tempfail_action parameter specifies the  ac-
	      tion after a temporary DNS error (default: defer_if_permit).

       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  into 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 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.

       This  feature  supports	a  limited  number  of $name attributes	in the
       footer text. These are replaced by their	current	 value	for  the  SMTP
       session:

       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_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_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  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	"/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 net-
       work 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_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_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 sender (MAIL
       FROM) addresses.

       Specify zero or more "type:table" lookup	tables.	With lookups from  in-
       dexed  files  such  as DB or DBM, or from networked tables such as NIS,
       LDAP or SQL, the	following search operations are	done with a sender ad-
       dress 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_mx_access type:table
	      Search the specified access(5) database for the MX hosts for the
	      MAIL FROM	address, 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 blacklists.	  This
	      feature is available in Postfix 2.1 and later.

       check_sender_ns_access type:table
	      Search  the specified access(5) database for the DNS servers for
	      the MAIL FROM address, 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	black-
	      lists.  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 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 final destination for the
	      sender  address,	and the	MAIL FROM domain has 1)	no DNS A or MX
	      record, or 2) a malformed	MX record such	as  a  record  with  a
	      zero-length MX hostname (Postfix version 2.3 and later).
	      The  unknown_address_reject_code parameter specifies the numeri-
	      cal response code	for rejected requests (default:	450).  The re-
	      sponse is	always 450 in case of a	temporary DNS error.
	      The  unknown_address_tempfail_action parameter specifies the ac-
	      tion after a temporary DNS error (default: defer_if_permit).

       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 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, the Postfix SMTP server de-
	      lays all responses by $smtpd_error_sleep_time seconds.

       o      With Postfix versions 2.0	and earlier, the Postfix  SMTP	server
	      delays all responses by (number of errors) seconds.

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.

       This feature is available in Postfix 2.2	and later.

smtpd_timeout (default:	normal:	300s, overload:	10s)
       The time	limit for sending a Postfix SMTP server	response and  for  re-
       ceiving	a  remote  SMTP	 client	request. 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.

       Time units: s (seconds),	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 certificate 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 certifi-
       cate 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 certificate  authori-
       ties  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 certificate 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   certificate	  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 certificate authorities to select the correct client certifi-
       cate.   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.

       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	 simi-
       lar software, it	will still insist on a server certificate.

       For servers that	are not	public Internet	MX hosts, Postfix 2.3 supports
       configurations with no certificates. This entails the use of  just  the
       anonymous TLS ciphers, which are	not supported by typical SMTP clients.
       Since such clients will not, as a rule, fall back to plain text after a
       TLS  handshake failure, the server will be unable to receive email from
       TLS enabled clients. To avoid accidental	configurations	with  no  cer-
       tificates, Postfix 2.3 enables certificate-less operation only when the
       administrator explicitly	sets "smtpd_tls_cert_file =  none".  This  en-
       sures that new Postfix configurations will not accidentally run with no
       certificates.

       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   or
       smtpd_tls_dcert_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_cipherlist (default: empty)
       Obsolete	Postfix	< 2.3 control for the Postfix SMTP server  TLS	cipher
       list.  It  is  easy  to create inter-operability	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.

       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.

       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/dh512.pem 512
	   openssl dhparam -out	/usr/local/etc/postfix/dh1024.pem 1024
	   openssl dhparam -out	/usr/local/etc/postfix/dh2048.pem 2048

       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 with Postfix version 2.2.

smtpd_tls_dh512_param_file (default: empty)
       File  with  DH  parameters that the Postfix SMTP	server should use with
       export-grade EDH	ciphers.

       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 with Postfix version 2.2.

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  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.

       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.

       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.

       The available choices are:

       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	 current best-practice
	      trade-off	between	security and computational efficiency. This is
	      the default in Postfix version 2.8 and later.

       ultra  Use  EECDH  with	approximately 192 bits of security at computa-
	      tional cost that is approximately	 twice	as  high  as  128  bit
	      strength	ECC. Barring significant progress in attacks on	ellip-
	      tic curve	crypto-systems,	the "strong" curve is  sufficient  for
	      most users.

       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: md5)
       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 algo-
       rithm is	md5, for backwards compatibility with Postfix  releases	 prior
       to 2.5.

       Advances	 in  hash  function cryptanalysis have led to md5 being	depre-
       cated in	favor of sha1.	However, as long as there are no known "second
       pre-image"  attacks  against  md5, its use in this context can still be
       considered 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.

       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 -sha1 -in	cert.pem
	   SHA1	Fingerprint=D4:6A:AB:19:24:79:F8:32: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. With OpenSSL 1.0.0 and	later, the "pkey" com-
       mand supports all key types. With OpenSSL 0.9.8 and  earlier,  the  key
       type  is	 always	 RSA  (nobody uses DSA,	and EC keys are	not fully sup-
       ported by 0.9.8), so the	"rsa" command is used.

	   # OpenSSL 1.0 with all certificates and SHA-1 fingerprints.
	   $ openssl x509 -in cert.pem -noout -pubkey |
	       openssl pkey -pubin -outform DER	|
	       openssl dgst -sha1 -c
	   (stdin)= 64:3f:1f:f6:e5:1e:d4:2a:56:8b:fc:09:1a:61:98:b5:bc:7c:60:58

	   # OpenSSL 0.9.8 with	RSA certificates and MD5 fingerprints.
	   $ openssl x509 -in cert.pem -noout -pubkey |
	       openssl rsa -pubin -outform DER |
	       openssl dgst -md5 -c
	   (stdin)= f4:62:60:f6:12:8f:d5:8d:28:4d:13:a7:db:b2:ff:50

       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.

       Note: Postfix 2.9.0-2.9.5 computed the public  key  fingerprint	incor-
       rectly.	To  use	 public-key  fingerprints, upgrade to Postfix 2.9.6 or
       later.

       Example:	client-certificate access table, with sha1 fingerprints:

	   /usr/local/etc/postfix/main.cf:
	       smtpd_tls_fingerprint_digest = sha1
	       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:F6:01:FB:2E:48:CD:AB:49:25:A2:3B
		   OK
	       85:16:78:FD:73:6E:CE:70:E0:31:5F: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.

       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  to  not
	      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	to not 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  to
	      not 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 to	not 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:	!SSLv2,	!SSLv3)
       The SSL/TLS protocols accepted by the Postfix SMTP server  with	manda-
       tory  TLS  encryption.  If  the	list is	empty, the server supports all
       available SSL/TLS protocol versions.  A non-empty value is  a  list  of
       protocol	 names	separated  by  whitespace, commas or colons.  The sup-
       ported protocol names are "SSLv2", "SSLv3" and  "TLSv1",	 and  are  not
       case  sensitive.	 The default value is "!SSLv2, !SSLv3" for Postfix re-
       leases after the	middle of 2015,	"!SSLv2" for older releases.

       With Postfix >= 2.5 the parameter syntax	was expanded to	support	proto-
       col   exclusions.   One	can  explicitly	 exclude  "SSLv2"  by  setting
       "smtpd_tls_mandatory_protocols =	!SSLv2". To exclude both  "SSLv2"  and
       "SSLv3"	set  "smtpd_tls_mandatory_protocols = !SSLv2, !SSLv3". Listing
       the protocols to	include, rather	than protocols	to  exclude,  is  sup-
       ported,	but  not  recommended. The exclusion form more closely matches
       the underlying OpenSSL interface	semantics.

       Note: As	of OpenSSL 1.0.1 two new protocols are defined,	"TLSv1.1"  and
       "TLSv1.2".  When	 Postfix  <=  2.5  is  linked against OpenSSL 1.0.1 or
       later, these, or	any other new protocol versions, cannot	 be  disabled.
       The  latest patch levels	of Postfix >= 2.6, and all versions of Postfix
       >= 2.10 can disable support for "TLSv1.1" or "TLSv1.2".

       Example:

       # Preferred syntax with Postfix >= 2.5:
       smtpd_tls_mandatory_protocols = !SSLv2, !SSLv3
       # Legacy	syntax:
       smtpd_tls_mandatory_protocols = TLSv1

       This feature is available in Postfix 2.3	and later.

smtpd_tls_protocols (default: !SSLv2, !SSLv3)
       List of TLS protocols that the Postfix SMTP server will exclude or  in-
       clude  with opportunistic TLS encryption. The default value is "!SSLv2,
       !SSLv3" for Postfix releases after the middle of	2015, empty for	 older
       releases	 allowing  all protocols to be used with opportunistic TLS.  A
       non-empty value is a list of protocol names  separated  by  whitespace,
       commas  or  colons.   The supported protocol names are "SSLv2", "SSLv3"
       and "TLSv1", and	are not	case sensitive.

       Note: As	of OpenSSL 1.0.1 two new protocols are defined,	"TLSv1.1"  and
       "TLSv1.2".  The latest patch levels of Postfix >= 2.6, and all versions
       of Postfix >= 2.10 can disable support for "TLSv1.1" or "TLSv1.2".

       To include a protocol list its name, to exclude	it,  prefix  the  name
       with  a	"!"  character.	 To  exclude  SSLv2  for opportunistic TLS set
       "smtpd_tls_protocols = !SSLv2". To exclude both "SSLv2" and "SSLv3" set
       "smtpd_tls_protocols  =	!SSLv2,	!SSLv3". Explicitly listing the	proto-
       cols to include,	rather than protocols to exclude,  is  supported,  but
       not  recommended.  The exclusion	form more closely matches the underly-
       ing OpenSSL interface semantics.

       Example:
       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.

       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.

       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 the non-standard "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 (smtps) was once chosen for this purpose.

       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.

       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.

       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.

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.

       Time  units:  s (seconds), 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.

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)
       The  mail  system  name that is prepended to the	process	name in	syslog
       records,	so that	"smtpd"	becomes, for example, "postfix/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 certificate  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  DANE	TLSA  digest algorithm agility.	 When digest algorithm
       agility is enabled, and the server and client support a	common	strong
       digest  algorithm,  TLSA	 records with weaker digest algorithms are ig-
       nored.

       Specify one of the following:

       off    DANE verification	examines each well-formed record in  the  TLSA
	      RRset whose matching type	is either "0" (no hash used) or	is one
	      of the digest algorithms listed in $tls_dane_digests.  This set-
	      ting is not recommended.

       on     From each	group of well-formed TLSA RRs a	non-zero digest	match-
	      ing type with the	same certificate usage and selector, DANE ver-
	      ification	 examines  only	 those records whose matching type has
	      the highest precedence (appear earliest in $tls_dane_digests).

       maybe  For compatibility	with digest algorithm agility,	each  certifi-
	      cate  or	public	key  whose  digest  is included	in a DANE TLSA
	      RRset, SHOULD be published with the same set of digest  matching
	      type  values  as	any  other  with  the same usage and selector.
	      Therefore, compatible TLSA  RRsets  will	contain	 an  identical
	      count of well-formed RRs with each non-zero digest matching type
	      for any fixed combination	of usage and selector.	When this con-
	      straint is violated, or any of the digest	records	are malformed,
	      digest algorithm agility will disabled.  Otherwise, digest algo-
	      rithm agility is enabled.

       Digest algorithm	agility	ensures	that the strongest digest supported by
       both the	Postfix	SMTP client and	the remote server is used, and	weaker
       digests	are ignored.  This supports non-disruptive deprecation of out-
       dated digest algorithms.

       To ensure compatibility with digest algorithm agility during key	 rota-
       tion,  when a certificate or public key is being	replaced with another,
       and both	are published during the transition, both the old and the  new
       certificate  MUST  be  specified	with the same set of digests.  One can
       change the list of digest algorithms later, once	old keys are  retired.
       At  any	given time, change either the list of digests without changing
       the list	of certificates	or public keys or the list of certificates  or
       public  keys without changing the list of digests.  Full	value matching
       type "0"	records	are not	subject	to this	constraint, but	 are  discour-
       aged due	to the size of the resulting DNS records.

       It  is expected that this algorithm agility mechanism will be published
       in a standards track RFC	for SMTP with DANE, and	also  in  an  eventual
       update to RFC 6698.

       This feature is available in Postfix 2.11 and later.

tls_dane_digests (default: sha512 sha256)
       RFC  6698 TLSA resource-record "matching	type" digest algorithms	in de-
       scending	preference order.  All the specified algorithms	must  be  sup-
       ported  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	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.

       When for	a particular combination of "certificate usage"	and "selector"
       the TLSA	RRset contains records with  more  than	 one  digest  matching
       type,  the tls_dane_digest_agility parameter determines whether all the
       RRs are used, or	only those with	the  most  preferred  digest  matching
       type.

       The  tls_dane_trust_anchor_digest_enable	parameter controls whether any
       digest TLSA records are acceptable in usage "2"	(trust	anchor	asser-
       tion) TLSA records.

       This feature is available in Postfix 2.11 and later.

tls_dane_trust_anchor_digest_enable (default: yes)
       RFC  6698  trust-anchor digest support in the Postfix TLS library.  En-
       able support for	RFC 6698 (DANE TLSA) DNS records that contain  digests
       of trust-anchors	with certificate usage "2".  In	this case the certifi-
       cate usage logically requires the server	administrator to configure the
       server to include the trust-anchor certificate in the server's SSL cer-
       tificate	chain.	If enough domains mess this up,	you can	 disable  sup-
       port  for  these	TLSA records, but you'll no longer have	secure connec-
       tions that get it right and only	publish	trust anchor records.

       At the dane security level, when	a TLSA RRset  includes	only  unusable
       associations,  the  Postfix  SMTP  client will automatically switch the
       connection to the encrypt security level.  At  the  dane-only  security
       level, the server in question is	skipped	and delivery is	deferred if no
       secure servers are found.

       The tls_dane_digests parameter controls the list	of  digest  algorithms
       that are	supported in TLSA records.  The	tls_dane_digest_agility	param-
       eter controls digest algorithm downgrade	attack resistance.

       This feature is available in Postfix 2.11 and later.

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.

       MICROSOFT_SESS_ID_BUG
	      See SSL_CTX_set_options(3)

       NETSCAPE_CHALLENGE_BUG
	      See SSL_CTX_set_options(3)

       LEGACY_SERVER_CONNECT
	      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.

       SSLREF2_REUSE_CERT_TYPE_BUG
	      See SSL_CTX_set_options(3)

       MICROSOFT_BIG_SSLV3_BUFFER
	      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.

       SSLEAY_080_CLIENT_DH_BUG
	      See SSL_CTX_set_options(3)

       TLS_D5_BUG
	      See SSL_CTX_set_options(3)

       TLS_BLOCK_PADDING_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!

       DONT_INSERT_EMPTY_FRAGMENTS
	      See SSL_CTX_set_options(3)

       CRYPTOPRO_TLSEXT_BUG
	      New with GOST support in OpenSSL 1.0.0.

       This feature is available in Postfix 2.8	and later.

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 4492. 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  an
       "exotic"	curve 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 4492. You	should	not  generally	change
       this setting.

       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:	ALL:+RC4:@STRENGTH)
       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 to
       not change this setting.

       This feature is available in Postfix 2.3	and later.

tls_high_cipherlist (default: ALL:!EXPORT:!LOW:!MEDIUM:+RC4:@STRENGTH)
       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	to not
       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: ALL:!EXPORT:+RC4:@STRENGTH)
       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	to not change this setting.

       This feature is available in Postfix 2.3	and later.

tls_medium_cipherlist (default:	ALL:!EXPORT:!LOW:+RC4:@STRENGTH)
       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  to  not	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_mandatory_tls_ciphers,  smtp_tls_mandatory_ciphers  and
       lmtp_tls_mandatory_ciphers.  You	are strongly encouraged	to not	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.

       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.

       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/arandom when  /dev/urandom	 gives
       timeout errors.

       This feature is available in Postfix 2.2	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 turn	all features by	specifying 0xFFFFFFFF,
       this is unlikely	to be a	good idea.

       LEGACY_SERVER_CONNECT
	      See SSL_CTX_set_options(3).

       NO_TICKET
	      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.

       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_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.

       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.

       This feature is available in Postfix 2.8	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.  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.

       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.	   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.

       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.

       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 elliptic-
       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.

       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.

       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  (seconds),
       m (minutes), h (hours), d (days), w (weeks).

       This feature is available in Postfix 2.8.

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.	 If you	use this  fea-
       ture  with  local files,	run "postmap /usr/local/etc/postfix/transport"
       after making a change.

       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.

       Time  units:  s (seconds), 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.

       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").

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.

       Time  units:  s (seconds), 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 Postfix SMTP server response code when a sender or	recip-
       ient address is rejected	by  the	 reject_unknown_sender_domain  or  re-
       ject_unknown_recipient_domain  restriction.  The	response is always 450
       in case of a temporary DNS error.

       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 an 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_domains (default:	$virtual_alias_maps)
       Postfix	is  final  destination for the specified list of virtual alias
       domains,	that is, domains for which all addresses are  aliased  to  ad-
       dresses in other	local or remote	domains. The SMTP server validates re-
       cipient addresses with $virtual_alias_maps and rejects non-existent re-
       cipients.   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 lookup string (the lookup result	is ig-
       nored).	Continue long lines by starting	the next line with whitespace.
       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 address.	The table format and lookups are docu-
       mented 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.

       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_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.

       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 final	destination for	the specified list of domains; mail is
       delivered via the $virtual_transport mail delivery transport.   By  de-
       fault  this  is the Postfix virtual(8) delivery agent.  The SMTP	server
       validates recipient addresses with  $virtual_mailbox_maps  and  rejects
       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.

       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.

       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.

       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

								   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_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: 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) | config_directory (default: see postconf -d output) | 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_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_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) | dnsblog_reply_delay (default: 0s) | dnsblog_service_name (default: dnsblog) | 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_recipient (default: MAILER-DAEMON) | empty_address_relayhost_maps_lookup_key (default: <>) | enable_errors_to (default: no) | enable_long_queue_ids (default: no) | enable_original_recipient (default: yes) | 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_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: all) | 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) | line_length_limit (default: 2048) | lmdb_map_size (default: 16777216) | lmtp_address_preference (default: ipv6) | lmtp_assume_final (default: no) | lmtp_bind_address (default: empty) | lmtp_bind_address6 (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_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_resolver_options (default: empty) | lmtp_dns_support_level (default: empty) | lmtp_enforce_tls (default: no) | 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_mx_address_limit (default: 5) | lmtp_mx_session_limit (default: 2) | lmtp_nested_header_checks (default: empty) | lmtp_per_record_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_ciphers (default: medium) | 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: md5) | 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: !SSLv2, !SSLv3) | lmtp_tls_note_starttls_offer (default: no) | lmtp_tls_per_site (default: empty) | lmtp_tls_policy_maps (default: empty) | lmtp_tls_protocols (default: !SSLv2, !SSLv3) | lmtp_tls_scert_verifydepth (default: 9) | lmtp_tls_secure_cert_match (default: nexthop) | lmtp_tls_security_level (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_use_tls (default: no) | lmtp_xforward_timeout (default: 300s) | local_command_shell (default: empty) | local_destination_concurrency_limit (default: 2) | local_destination_recipient_limit (default: 1) | local_header_rewrite_clients (default: permit_inet_interfaces) | 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) | 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_reject_characters (default: empty) | message_size_limit (default: 10240000) | message_strip_characters (default: empty) | 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_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: subnet) | myorigin (default: $myhostname) | nested_header_checks (default: $header_checks) | newaliases_path (default: see postconf -d output) | non_fqdn_reject_code (default: 504) | non_smtpd_milters (default: empty) | notify_classes (default: resource, software) | owner_request_special (default: yes) | parent_domain_matches_subdomains (default: see postconf -d output) | permit_mx_backup_networks (default: empty) | pickup_service_name (default: pickup) | plaintext_reject_code (default: 450) | postmulti_control_commands (default: reload flush) | postmulti_start_commands (default: start) | postmulti_stop_commands (default: see postconf -d output) | postscreen_access_list (default: permit_mynetworks) | postscreen_bare_newline_action (default: ignore) | postscreen_bare_newline_enable (default: no) | postscreen_bare_newline_ttl (default: 30d) | postscreen_blacklist_action (default: ignore) | postscreen_cache_cleanup_interval (default: 12h) | postscreen_cache_map (default: btree:$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: ${stress?10}${stress:300}s) | 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_reply_map (default: empty) | postscreen_dnsbl_sites (default: empty) | postscreen_dnsbl_threshold (default: 1) | 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: ${stress?2}${stress:6}s) | 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_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: $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) | 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_throttle_time (default: 60s) | setgid_group (default: postdrop) | show_user_unknown_table_name (default: yes) | showq_service_name (default: showq) | smtp_address_preference (default: any) | smtp_always_send_ehlo (default: yes) | smtp_bind_address (default: empty) | smtp_bind_address6 (default: empty) | 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_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_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_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_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_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_cipherlist (default: empty) | smtp_tls_ciphers (default: medium) | 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: md5) | 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: !SSLv2, !SSLv3) | smtp_tls_note_starttls_offer (default: no) | smtp_tls_per_site (default: empty) | smtp_tls_policy_maps (default: empty) | smtp_tls_protocols (default: !SSLv2, !SSLv3) | smtp_tls_scert_verifydepth (default: 9) | smtp_tls_secure_cert_match (default: nexthop, dot-nexthop) | smtp_tls_security_level (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_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_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_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) | 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_milters (default: empty) | 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_policy_service_max_idle (default: 300s) | smtpd_policy_service_max_ttl (default: 1000s) | smtpd_policy_service_timeout (default: 100s) | 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_unlisted_recipient (default: yes) | smtpd_reject_unlisted_sender (default: no) | 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_path (default: smtpd) | 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_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: md5) | 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: !SSLv2, !SSLv3) | smtpd_tls_protocols (default: !SSLv2, !SSLv3) | 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) | 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) | 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_strong_curve (default: prime256v1) | tls_eecdh_ultra_curve (default: secp384r1) | tls_export_cipherlist (default: ALL:+RC4:@STRENGTH) | tls_high_cipherlist (default: ALL:!EXPORT:!LOW:!MEDIUM:+RC4:@STRENGTH) | tls_legacy_public_key_fingerprints (default: no) | tls_low_cipherlist (default: ALL:!EXPORT:+RC4:@STRENGTH) | tls_medium_cipherlist (default: ALL:!EXPORT:!LOW:+RC4:@STRENGTH) | 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_ssl_options (default: empty) | tls_wildcard_matches_multiple_labels (default: yes) | tlsmgr_service_name (default: tlsmgr) | 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_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) | 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_domains (default: $virtual_alias_maps) | virtual_alias_expansion_limit (default: 1000) | virtual_alias_maps (default: $virtual_maps) | virtual_alias_recursion_limit (default: 1000) | 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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