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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
		     recursively 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
       default 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
       defer 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
       address 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_dependent_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_depen-
       dent_relayhost_maps)
       Overrides  the  sender_dependent_relayhost_maps	parameter  setting for
       address 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
       addresses 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
       :include:  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
	      $local_header_rewrite_clients,

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

       To   get	  the	behavior   before   Postfix   version	2.2,   specify
       "local_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
       addresses  cannot  match	 Postfix access	tables,	because	the address is
       ambiguous.

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
       implements 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
       itself.

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 "@$myorigin" to mail
       addresses without domain	information.  With  remotely  submitted	 mail,
       append the string "@$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
	      $local_header_rewrite_clients,

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

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

append_dot_mydomain (default: yes)
       With   locally  submitted  mail,	 append	 the  string  ".$mydomain"  to
       addresses that have no ".domain"	information. With  remotely  submitted
       mail, append the	string ".$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
	      $local_header_rewrite_clients,

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

       To   get	  the	behavior   before   Postfix   version	2.2,   specify
       "local_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
       replaced	by its contents; a "type:table"	lookup table is	matched	when a
       table  entry  matches  a	 lookup	string (the lookup result is ignored).
       Continue	long lines by starting the next	line with whitespace.  Specify
       "!pattern"  to  exclude	an address or network block from the list. The
       form "!/file/name" is supported only in Postfix version 2.4 and later.

       Note: IP	version	6 address information must be specified	inside	[]  in
       the   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
       local MTA is the	best SMTP mail exchanger for a destination not	listed
       in    $mydestination,	$inet_interfaces,   $proxy_interfaces,	 $vir-
       tual_alias_domains, or $virtual_mailbox_domains.	 By default, the Post-
       fix 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-
       delivery	 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
       obsolete	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
       default,	 canonical_maps	 address mapping is applied to envelope	sender
       and recipient addresses,	and to	header	sender	and  header  recipient
       addresses.

       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
       envelopes.  The	mapping	 is  applied  to  both	sender	and  recipient
       addresses, in both envelopes and	in headers,  as	 controlled  with  the
       canonical_classes  parameter.  This is typically	used to	clean up dirty
       addresses 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
       ADDRESS_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
	      $local_header_rewrite_clients,

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

       To   get	  the	behavior   before   Postfix   version	2.2,   specify
       "local_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
       deferred.

       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
       tables: 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
       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).

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	  par-
       ent_domain_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
       invoked 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.,
       invocations  of	delivery  agents) than the current message counter has
       accumulated (or will eventually	accumulate  -  see  about  slot	 loans
       below).	This parameter controls	how often is the counter incremented -
       it happens after	each default_delivery_slot_cost	recipients  have  been
       delivered.

       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
       required	 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
       required	 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
       before a	specific destination is	considered  unavailable	 (and  further
       delivery	 is suspended).	Specify	zero to	disable	this feature. A	desti-
       nation'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
       $default_destination_concurrency_failed_cohort_limit	(or    $trans-
       port_destination_concurrency_failed_cohort_limit).  To make the	sched-
       uler  completely	 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
       increases until it  reaches  the	 per-destination  maximal  concurrency
       limit. With positive feedback, concurrency is incremented at the	end of
       a sequence with length 1/feedback. This is  unlike  negative  feedback,
       where  concurrency  is decremented at the start of a sequence of	length
       1/feedback.

       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
	      domain.  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
	      domain into concurrency of deliveries  to	 the  same  recipient.
	      Different	 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
       requested from an aliases(5) file that is owned by root,	or when	deliv-
       ery  is done on behalf of root. DO NOT SPECIFY A	PRIVILEGED USER	OR THE
       POSTFIX OWNER.

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

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

       This feature is available in Postfix 2.0	and later.

       The template 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_unknown_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
	      domain 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_interfaces, $virtual_alias_domains, $virtual_mailbox_domains, or
       $relay_domains.	 This  information   can   be	overruled   with   the
       sender_dependent_default_transport_maps	parameter  and with the	trans-
       port(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
       domain.

       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
       explicit	 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
       order 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
       instead 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
       default	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
       migration (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
	      "enable_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
       duplicate elimination on	distinct pairs of (original recipient, rewrit-
       ten 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
       returns 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
       between	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
       default	  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
       altogether.

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
       address 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
       accepting connections. Specify one or more of "ipv4" or	"ipv6",	 sepa-
       rated  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
       before 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
       parameter.  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
       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).

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
       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 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
       insensitive 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
       parameter. 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
       parameter.  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_secu-
       rity_options)
       The   LMTP-specific   version   of   the	  smtp_sasl_tls_verified_secu-
       rity_options 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
       authentication.	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)
       delivery	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
       parameter.  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
       parameter.  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
       parameter.  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
       parameter.  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
       parameter.  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
       parameter. 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
       parameter. 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
       details 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
	      result is	ignored, and no	subnet lookup is done. This  is	 suit-
	      able 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
       addresses.

	   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
       local 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_interfaces	or $proxy_interfaces.  Specify @domain as a  wild-card
       for  domains  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
       delivery	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
       chroot  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
       information 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
       default,	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/local/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.minor.patchlevel. Experimental releases also include the  release
       date. The version string	can be used in,	for example, the SMTP greeting
       banner.

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
       parameter 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
       deliveries 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,
       reject_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
       addresses,  and	to header sender and header recipient addresses.  This
       allows you to use address masquerading on a mail	 gateway  while	 still
       being 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
	      $local_header_rewrite_clients,

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

       To   get	  the	behavior   before   Postfix   version	2.2,   specify
       "local_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
       intentional.

       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
       default	protocol  is  2.  Postfix sends	this version number during the
       initial 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
       instance,  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
       invokes	  the	 multi-instance	   manager    specified	   with	   the
       multi_instance_wrapper  parameter.  The	multi-instance manager in turn
       executes	postfix(1) commands for	the default instance and for all Post-
       fix instances 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
       addressed to user@[the.net.work.address]	of the	mail  system  (the  IP
       addresses  specified  with  the	inet_interfaces	 and  proxy_interfaces
       parameters).

       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
	      machine.	 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.
	      Instead,	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
       default	is  to report only the most serious problems. The paranoid may
       wish to turn on the policy (UCE and mail	relaying) and  protocol	 error
       (broken mail software) reports.

       NOTE:  postmaster  notifications	 may  contain confidential information
       such as SASL passwords or message content.  It is the  system  adminis-
       trator's	responsibility to treat	such information with care.

       The error classes are:

       bounce (also implies 2bounce)
	      Send  the	 postmaster copies of the headers of bounced mail, and
	      send transcripts of SMTP sessions	when Postfix rejects mail. The
	      notification   is	  sent	to  the	 address  specified  with  the
	      bounce_notice_recipient configuration parameter (default:	 post-
	      master).

       2bounce
	      Send undeliverable bounced mail to the postmaster. The notifica-
	      tion   is	  sent	 to   the   address   specified	   with	   the
	      2bounce_notice_recipient configuration parameter (default: post-
	      master).

       data   Send the postmaster a transcript of the  SMTP  session  with  an
	      error  because a critical	data file was unavailable. The notifi-
	      cation   is   sent   to	the   address	specified   with   the
	      error_notice_recipient  configuration  parameter (default: post-
	      master).
	      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_notice_recipient configuration parameter  (default:	 post-
	      master).

       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
	      (default:	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
	      (default:	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
       really 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
       rejected	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
       instance	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
       return.	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)
       instances,   use	 "postscreen_cache_map	=  proxy:btree:/path/to/file".
       This requires Postfix version 2.9 or later; earlier proxymap(8)	imple-
       mentations 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
       insensitive  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:,
       except 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"
       information 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
	      remote  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
       parameter.

       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
       already	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_enforce_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
       attribute 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
       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_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
       because 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
       receive 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
       receive 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_upstream_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_upstream_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
       addresses 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
       detection.

       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,
       especially 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
       request 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
       indexed by the RBL domain name. By default, Postfix  uses  the  default
       template	 as specified with the default_rbl_reply configuration parame-
       ter. 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)
	      recipients. This is typically specified BEFORE an	external  con-
	      tent 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
       recipient address.  The BCC address  (multiple  results	are  not  sup-
       ported) 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
	      address 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_interfaces.

       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
       implements 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
       itself.

       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
       envelope	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"
       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.

       For  finer  control, see: unverified_recipient_tempfail_action, unveri-
       fied_sender_tempfail_action,    unknown_address_tempfail_action,	   and
       unknown_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
       appropriate  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
       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
       relay_destination_concurrency_limit from	concurrency  per  domain  into
       concurrency 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
       relay  mail  to.	 Subdomain  matching  is  controlled  with  the	  par-
       ent_domain_matches_subdomains  parameter.  For  details	about  how the
       relay_domains  value  is	 used,	see  the  description  of   the	  per-
       mit_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
       addresses with $relay_recipient_maps and	rejects	 non-existent  recipi-
       ents.   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
       reject 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
       domain. 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
       information.

       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
       domains 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
       parameter 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
       addresses  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
       local(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
       addresses as soon as they come out of child alias expansion.  If	deliv-
       ery 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
       inside quotes.

       By default, the Postfix address resolver	does  not  quote  the  address
       localpart  as  per  RFC	822, so	that additional	@ or % or !  operators
       remain visible. This behavior is	safe but it is also technically	incor-
       rect.

       If  you	specify	 "resolve_dequoted_address  =  no",  then  the Postfix
       resolver	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
       addresses 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
       addresses  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
	      address 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_interfaces.

       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
       implements 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
       itself.

       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
       addresses.

       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_depen-
       dent_default_transport_maps,  default_transport	and  with  the	trans-
       port(5) table.

       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
	      exists 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
       appears 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"
       responses.   The	 extra	detail	makes trouble shooting easier but also
       reveals 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
       improve 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
	      defined 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
       unused  SMTP  client  socket  is	kept open before it is closed.	Do not
       specify 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
       repeatedly.  The	timer starts when the connection is initiated (i.e. it
       includes	 the  connect,	greeting  and helo latency, in addition	to the
       latencies 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
       becomes 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
       until 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
       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 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
       insensitive  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
	      domains. 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
	      Internet.	 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
	      request  DNSSEC-validated	 responses.  If	 the  MX  response  is
	      DNSSEC-validated the corresponding hostnames are considered val-
	      idated.

       o      The address lookups of validated hostnames are  also  validated,
	      (provided	 of  course  "smtp_host_lookup"	 includes  "dns",  see
	      below).

       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
       relies on the system's  configured  DNSSEC-validating  recursive	 name-
       server  to  perform  all	 DNSSEC	 validation.   Since this nameserver's
       DNSSEC-validated	responses will be fully	trusted, it is strongly	recom-
       mended  that  the  MTA  host  have  a local DNSSEC-validating recursive
       caching nameserver 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_enforce_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
       address.	 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_always_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
       indexed	by  hostname  for  consistency	 with	smtp_discard_ehlo_key-
       word_address_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
       involve	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
       instead	 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
       directory 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
       removed.

       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
       ignored.	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-
       dependent authentication	is enabled.  If	no username:password entry  is
       found, then the Postfix SMTP client will	not attempt to authenticate to
       the remote host.

       The Postfix SMTP	client opens the lookup	table before going  to	chroot
       jail, so	you can	leave the password file	in /usr/local/etc/postfix.

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_secu-
       rity_options)
       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
       either 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
       authentication.	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_exclude_ciphers	 are  excluded from the	base definition	of the
       selected	cipher 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
       cipherlist, 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
       encryption  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
       attribute, 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"
       attacks,	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
       example:

	   $ 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
       appropriate 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
       unlikely	to ever	yield DNSSEC validated results,	since child  zones  of
       unsigned	 zones are also	unsigned in the	absence	of DLV or locally con-
       figured 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  interoper-
       ability	problems with nameservers for unsigned zones that are not pre-
       pared 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_exclude_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_ciphers	(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"
       attribute. 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
       require	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_enforce_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
       introduced 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
       enable  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,
       $relay_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
       domain  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,
	      demanding	stronger than  default	TLS  security  merely  reduces
	      inter-operability. The optional "ciphers", "exclude" and "proto-
	      cols" attributes (available for opportunistic TLS	 with  Postfix
	      >=       2.6)	  override	 the	   "smtp_tls_ciphers",
	      "smtp_tls_exclude_ciphers" and  "smtp_tls_protocols"  configura-
	      tion parameters. When opportunistic TLS handshakes fail, Postfix
	      retries the connection with  TLS	disabled.   This  allows  mail
	      delivery to sites	with non-interoperable 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
	      obtained	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
	      digest  algorithm	 used to calculate the fingerprint is selected
	      by the smtp_tls_fingerprint_digest parameter.  Multiple  finger-
	      prints  can  be  combined	with a "|" delimiter in	a single match
	      attribute, or multiple match attributes can be employed. The ":"
	      character	 is  not used as a delimiter as	it occurs 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
       include	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,
       using 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
	      secure 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
	      appropriate 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
	      cipher  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
       issuing	parent	certificates will be ignored.  Specify a list of path-
       names 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
	      labels  followed by a .example.com suffix. Case distinctions are
	      ignored.

       Strategies specify a transformation from	the  next-hop  domain  to  the
       expected	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
	      ignored.

       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,
       delivery	 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
       replaced	by its contents; a "type:table"	lookup table is	matched	when a
       table entry matches a lookup string (the	 lookup	 result	 is  ignored).
       Continue	 long lines by starting	the next line with whitespace. Specify
       "!pattern" to exclude an	address	or network block from  the  list.  The
       form "!/file/name" is supported only in Postfix version 2.4 and later.

       Note:  IP  version 6 address information	must be	specified inside [] in
       the smtpd_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
       access control. Typical use is for SMTP-based content  filters,	fetch-
       mail-like  programs,  or	 SMTP  server  access  rule  testing.  See the
       XCLIENT_README document for details.

       This feature is available in Postfix 2.1	and later.

       By default, no clients are allowed to specify XCLIENT.

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

       Note:  IP  version 6 address information	must be	specified inside [] in
       the smtpd_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
       details.

       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
       replaced	by its contents; a "type:table"	lookup table is	matched	when a
       table  entry  matches  a	 lookup	string (the lookup result is ignored).
       Continue	long lines by starting the next	line with whitespace.  Specify
       "!pattern"  to  exclude	an address or network block from the list. The
       form "!/file/name" is supported only in Postfix version 2.4 and later.

       Note: IP	version	6 address information must be specified	inside	[]  in
       the  smtpd_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
       allowed 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.
       Restrictions  are applied in the	order as specified; the	first restric-
       tion 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
	      require 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.
	      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_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
	      access(5)	manual page for	details.  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	avail-
	      able 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_interfaces.

       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_domain.
	      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_reply_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
	      DEFER_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
	      exceptions.
	      For  safety,  permit_rhswl_client	 is  silently  ignored when it
	      would  override  reject_unauth_destination.    The   result   is
	      DEFER_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
	      additional  RBL  related configuration parameters.  This feature
	      is available in Postfix 2.8 and later.

       reject_unknown_client_hostname	   (with      Postfix	   <	  2.3:
       reject_unknown_client)
	      Reject  the  request when	1) the client IP address->name mapping
	      fails,  2)  the  name->address  mapping	fails,	 or   3)   the
	      name->address mapping does not match the client IP address.
	      This	is     a     stronger	  restriction	  than	   the
	      reject_unknown_reverse_client_hostname feature,  which  triggers
	      only under condition 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
	      address->name mapping.
	      This	is	a      weaker	  restriction	  than	   the
	      reject_unknown_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
	      NOTIFY=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,
	      because the total	number of recipients is	not known at  an  ear-
	      lier 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
	      reject_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_recipient_restrictions parameters. When  helo,  sender  or
	      recipient	 restrictions  are  listed under smtpd_client_restric-
	      tions, 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
	      domain 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.
       Restrictions are	applied	in the order as	specified; the first  restric-
       tion 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
       recipient 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
       insensitive  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
       after 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
       "Delayed	 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.
       Restrictions are	applied	in the order as	specified; the first  restric-
       tion 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
       escapes 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
       under 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
       require 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
       "Delayed	 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
       restriction  (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.
       Restrictions are	applied	in the order as	specified; the first  restric-
       tion that matches wins.

       The  following  restrictions  are  specific to the hostname information
       received	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
	      action.  Note: specify  "smtpd_helo_required  =  yes"  to	 fully
	      enforce 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.
	      Instead, use DUNNO in  order  to	exclude	 specific  hosts  from
	      blacklists.   Note  2:  specify  "smtpd_helo_required  = yes" to
	      fully enforce this restriction (without  "smtpd_helo_required  =
	      yes", a client can simply	skip check_helo_mx_access by not send-
	      ing 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.
	      Instead, use DUNNO in  order  to	exclude	 specific  hosts  from
	      blacklists.   Note  2:  specify  "smtpd_helo_required  = yes" to
	      fully enforce this restriction (without  "smtpd_helo_required  =
	      yes", a client can simply	skip check_helo_ns_access by not send-
	      ing 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:
       reject_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
	      enforce 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
	      reject_rbl_client	description for	additional RBL related config-
	      uration 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	 send-
	      ing  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
	      described	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_restrictions,	  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
       ignored).   Continue  long  lines by starting the next line with	white-
       space. 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-
       recipient 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
       receiving 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
       recipient.

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
       restriction 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.
       Restrictions  are applied in the	order as specified; the	first restric-
       tion 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
	      address  contains	 no   sender-specified	 routing   (user@else-
	      where@domain).

       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
	      access 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
	      parameter	  specifies   the   default   server  reply;  and  the
	      rbl_reply_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
	      response is always 450 in	case of	a temporary DNS	error.
	      The   unknown_address_tempfail_action  parameter	specifies  the
	      action 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_reject_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
	      details.
	      The  unverified_recipient_reject_code  parameter	specifies  the
	      numerical	 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_recipient_defer_code  parameter	specifies  the
	      numerical	response code when an address probe failed  due	 to  a
	      temporary	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
       restriction 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_recipient_maps, and $local_recipient_maps is not null.

       o      The recipient  domain  matches  $virtual_alias_domains  but  the
	      recipient	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_recipi-
       ent_restrictions.

       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
       require a login and password whenever AUTH  is  offered,	 whether  it's
       necessary  or  not.  To work around this, specify, for example, $mynet-
       works 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
       order  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
       behave 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
       authentication.	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
       indexed 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
       address of user@domain:

       1) user@domain
	      This table lookup	is always done and has the highest precedence.

       2) user
	      This table lookup	is done	only  when  the	 domain	 part  of  the
	      sender  address  matches $myorigin, $mydestination, $inet_inter-
	      faces or $proxy_interfaces.

       3) @domain
	      This table lookup	is done	last and has the lowest	precedence.

       In all cases the	result of table	lookup must be either "not found" or a
       list of SASL login names	separated by comma and/or whitespace.

smtpd_sender_restrictions (default: empty)
       Optional	 restrictions that the Postfix SMTP server applies in the con-
       text of a client	MAIL FROM command.  See	 SMTPD_ACCESS_README,  section
       "Delayed	 evaluation of SMTP access restriction lists" for a discussion
       of evaluation context and time.

       The default is to permit	everything.

       Specify a list of restrictions, separated by commas and/or  whitespace.
       Continue	 long  lines  by  starting  the	 next  line  with  whitespace.
       Restrictions are	applied	in the order as	specified; the first  restric-
       tion 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
	      address,	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.
	      Instead,	use  DUNNO  in	order  to  exclude specific hosts from
	      blacklists.  This	feature	is available in	Postfix	2.1 and	later.

       reject_authenticated_sender_login_mismatch
	      Enforces	the   reject_sender_login_mismatch   restriction   for
	      authenticated 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
	      parameter	 specifies  the	 default   server   reply;   and   the
	      rbl_reply_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
	      response is always 450 in	case of	a temporary DNS	error.
	      The  unknown_address_tempfail_action  parameter  specifies   the
	      action 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
	      details.
	      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
	      response 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_delay_reject = yes", so  that  $smtpd_sender_restrictions
	      is evaluated 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
       responses.

       o      With Postfix version 2.1 and  later,  the	 Postfix  SMTP	server
	      delays 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
       receiving 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
       using 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
       requested, 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
       requested, 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
       announce	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
       ensures 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_exclude_ciphers are excluded from the base definition of  the
       selected	 cipher	 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
       parameters 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
       instances.  If you prefer, you can  generate  separate  parameters  for
       each instance.

       If  you	want  to  take maximal advantage of ciphers that offer forward
       secrecy 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
       secrecy 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
       interoperability	 problems.  DO NOT exclude ciphers unless it is	essen-
       tial to do so. This is not an OpenSSL cipherlist; 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):

	   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
       example:

	   $ 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
       appropriate 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
       ciphers.	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
	      underlying 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
	      cipherlist  is  specified	via the	tls_high_cipherlist configura-
	      tion 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  =
       aNULL".

       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_ciphers (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
       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
       "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
       include	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	white-
       space, 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.
	      According	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"
       implies "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
       library	(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
       remote	   address	and	 port	   information.	       Specify
       "smtpd_upstream_proxy_protocol  = haproxy" to enable the	haproxy	proto-
       col.

       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_upstream_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
       information.  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	"mail-
       box_delivery_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
	      $local_header_rewrite_clients,

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

       To   get	  the	behavior   before   Postfix   version	2.2,   specify
       "local_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
       accessing 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
       errors  while  parsing  the  command  line  arguments, and errors while
       accessing 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
       ignored.

       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
       descending 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
       ignored 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.
       Enable support for RFC  6698  (DANE  TLSA)  DNS	records	 that  contain
       digests	of trust-anchors with certificate usage	"2".  In this case the
       certificate usage logically requires the	server administrator  to  con-
       figure  the  server  to	include	 the  trust-anchor  certificate	in the
       server's	SSL certificate	chain.	If enough domains mess	this  up,  you
       can  disable  support for these TLSA records, but you'll	no longer have
       secure connections 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
       after  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
       attacks.	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
       secrecy 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
       attacks.	 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
       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.

       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
       secrecy 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
       defines	the  meaning  of  the  "export"	 setting in smtpd_tls_ciphers,
       smtpd_tls_mandatory_ciphers,	smtp_tls_ciphers,      smtp_tls_manda-
       tory_ciphers,  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	default	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_manda-
       tory_ciphers,	   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
       encouraged 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
       defines	the  meaning  of  the  "medium"	 setting in smtpd_tls_ciphers,
       smtpd_tls_mandatory_ciphers,	smtp_tls_ciphers,      smtp_tls_manda-
       tory_ciphers,  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 certifi-
       cates).	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
       cipher 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
       issues.	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 implementation is	flawed.	Most notably  Windows  2003  Microsoft
       Exchange	 servers  have	flawed	implementations	of DES-CBC3-SHA, which
       OpenSSL considers stronger than RC4-SHA.	 Enabling server  cipher-suite
       selection  may  create interoperability issues with Windows 2003	Micro-
       soft 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	${con-
       fig_directory}/prng_exch	to ${data_directory}/prng_exch.	 As  a	migra-
       tion  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
       enable 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
       upper 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
       enabled	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
	      library.	 Compression  is CPU-intensive,	and compression	before
	      encryption 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
       details.

       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_manda-
       tory_exclude_ciphers)
       Additional  list	 of  ciphers  or  cipher  types	 to  exclude  from the
       tlsproxy(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
       parameter value,	where transport	is the master.cf name of  the  message
       delivery	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
       details.

       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:  "_recipi-
       ent_refill_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:  "_recipi-
       ent_refill_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
       reject_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_unknown_client_hostname  restriction.  The  SMTP	server	always
       replies	with 450 when the mapping failed due to	a temporary error con-
       dition.

       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_unknown_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
       address 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_interfaces.

       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
       local_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
       enhanced	 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"
       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.

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
       address 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"
       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.

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
       addresses in other local	or remote domains. The SMTP  server  validates
       recipient  addresses  with $virtual_alias_maps and rejects non-existent
       recipients.  See	 also  the  virtual  alias   domain   class   in   the
       ADDRESS_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
       information 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
       information 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
       ignored).   Continue  long  lines by starting the next line with	white-
       space. Specify "!pattern" to exclude a host or  domain  name  from  the
       list.  The  form	"!/file/name" is supported only	in Postfix version 2.4
       and later.

       See also	the VIRTUAL_README and ADDRESS_CLASS_README documents for fur-
       ther information.

       Example:

       virtual_alias_domains = virtual1.tld virtual2.tld

virtual_alias_expansion_limit (default:	1000)
       The  maximal  number of addresses that virtual alias expansion produces
       from each original recipient.

       This feature is available in Postfix 2.1	and later.

virtual_alias_maps (default: $virtual_maps)
       Optional	lookup tables that alias specific mail addresses or domains to
       other  local or remote 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/local/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)
       delivery	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
       default 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
       deliveries 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
       assumed 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)
       delivery	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)
       addresses 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:	  vir-
       tual_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)
       delivery	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: | address_verify_sender_dependent_relayhost_maps (default: $sender_depen- | 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_secu- | 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_secu- | 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_manda- | 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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