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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 a small subset	of all
       the parameters that control the operation of the	Postfix	 mail  system.
       Parameters not specified	in main.cf are left at their default values.

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

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

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

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

       o      A	parameter value	may refer to other parameters.

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

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

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

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

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

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

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

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

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

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

       Do  not	change	this  unless  you have a complete understanding	of RFC
       2821.

       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
       2821.

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: empty)
       Optional	lookup table for persistent address verification status	 stor-
       age.   The  table is maintained by the verify(8)	service, and is	opened
       before the process releases privileges.

       By default, the information is kept in volatile memory, and is lost af-
       ter "postfix reload" or "postfix	stop".

       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
       the file	and do "postfix	reload".

       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.

       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: 3)
       How many	times to query the verify(8) service for the completion	of  an
       address verification request in progress.

       The default poll	count is 3.

       Specify 1 to implement a	crude form of greylisting, that	is, always de-
       fer the first delivery request for a never seen before address.

       Example:

       address_verify_poll_count = 1

       This feature is available in Postfix 2.1	and later.

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

       The default polling delay is 3 seconds.

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

       This feature is available in Postfix 2.1	and later.

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

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

       This feature is available in Postfix 2.1	and later.

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

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

       This feature is available in Postfix 2.1	and later.

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

       This feature is available in Postfix 2.1	and later.

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

       This feature is available in Postfix 2.1	and later.

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

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

       Examples:

       address_verify_sender = <>
       address_verify_sender = postmaster@my.domain

       This feature is available in Postfix 2.1	and later.

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

       This feature is available in Postfix 2.3	and later.

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

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

       This feature is available in Postfix 2.1	and later.

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

       This feature is available in Postfix 2.1	and later.

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

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

       Examples:

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

alias_maps (default: see postconf -d output)
       The alias databases that	are used for local(8) delivery.	See aliases(5)
       for syntax details.

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

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

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

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

       Examples:

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

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

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

       Example:

       allow_mail_to_commands =	alias,forward,include

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

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

       Example:

       allow_mail_to_files = alias,forward,include

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

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

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

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

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

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

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

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

       Example:

       allow_percent_hack = no

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

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

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

alternate_config_directories (default: empty)
       A list of non-default Postfix configuration  directories	 that  may  be
       specified  with	"-c  config_directory" on the command line, or via the
       MAIL_CONFIG environment parameter.

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

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

       Note:  if  mail	to  the	BCC address bounces it will be returned	to the
       sender.

       Note: automatic BCC recipients are produced  only  for  new  mail.   To
       avoid mailer loops, automatic BCC recipients are	not generated for mail
       that Postfix forwards internally, nor for mail that  Postfix  generates
       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 "@$myorigin" to mail ad-
       dresses	without	 domain	information. With remotely submitted mail, ap-
       pend the	string "@$remote_header_rewrite_domain"	instead.

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

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

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

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

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

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

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

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

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

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

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

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

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

application_event_drain_time (default: 100s)
       How  long  the  postkick(1)  command  waits  for	a request to enter the
       server's	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 SMTP clients are allowed to	specify	the XVERP command.  This  com-
       mand requests that mail be delivered one	recipient at a time with a per
       recipient return	address.

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

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

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

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

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

       This feature is available in Postfix 2.1	and later.

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

       This feature is available in Postfix 2.0	and later.

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

       This feature is available in Postfix 2.0	and later.

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

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

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

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

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

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

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

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

       This feature is available in Postfix 2.0	and later.

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

bounce_queue_lifetime (default:	5d)
       The maximal time	a bounce message is queued before it is	considered un-
       deliverable.   By  default, this	is the same as the queue life time for
       regular mail.

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

       Specify 0 when mail delivery should be tried only once.

       This feature is available in Postfix 2.1	and later.

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

       This feature is available in Postfix 2.0	and later.

bounce_size_limit (default: 50000)
       The maximal amount of original message text that	is sent	in  a  non-de-
       livery  notification. Specify a byte count. With	Postfix	2.4 and	later,
       a message is returned as	either message/rfc822 (the complete  original)
       or  as  text/rfc822-headers  (the  headers only).  With earlier Postfix
       versions, a message is always returned as message/rfc822	and  is	 trun-
       cated 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 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 de-
       fault, canonical_maps address mapping is	applied	to envelope sender and
       recipient  addresses,  and  to  header  sender and header recipient ad-
       dresses.

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

       This feature is available in Postfix 2.2	and later.

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

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

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

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

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

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

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

       Examples:

       canonical_maps =	dbm:/usr/local/etc/postfix/canonical
       canonical_maps =	hash:/usr/local/etc/postfix/canonical

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

       This feature is available in Postfix 2.0	and later.

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

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

       The following $name expansions are done on  command_execution_directory
       before  the  directory  is changed. Expansion happens in	the context of
       the delivery request.  The result of $name expansion is	filtered  with
       the character set that is specified with	the execution_directory_expan-
       sion_filter parameter.

       $user  The recipient's username.

       $shell The recipient's login shell pathname.

       $home  The recipient's home directory.

       $recipient
	      The full recipient address.

       $extension
	      The optional recipient address extension.

       $domain
	      The recipient domain.

       $local The entire recipient localpart.

       $recipient_delimiter
	      The system-wide recipient	address	extension delimiter.

       ${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)
       The name	of a mail delivery transport that filters  mail	 after	it  is
       queued.

       This parameter uses the same syntax as the right-hand side of a Postfix
       transport(5) table. This	setting	has a lower precedence than a  content
       filter	that   is   specified	with   an  access(5)  table  or	 in  a
       header_checks(5)	or body_checks(5) table.

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

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

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

       This feature is available in Postfix 2.5	and later.

debug_peer_level (default: 2)
       The increment in	verbose	logging	level when a remote client  or	server
       matches a pattern in the	debug_peer_list	parameter.

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

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

       Pattern	matching  of  domain  names  is	 controlled  by	the parent_do-
       main_matches_subdomains parameter.

       Examples:

       debug_peer_list = 127.0.0.1
       debug_peer_list = some.domain

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

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

       Example:

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

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

       Examples:

       default_database_type = hash
       default_database_type = dbm

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

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

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

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

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

       Examples:

       default_delivery_slot_cost = 0
       default_delivery_slot_cost = 2

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

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

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

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

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

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

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

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

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

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

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

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

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

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

       Specify one of the following forms:

       number

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

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

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

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

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

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

       Specify one of the following forms:

       number

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

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

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

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

       This feature is available in Postfix 2.5	and later.

default_destination_rate_delay (default: 0s)
       The default amount of delay that	is inserted between individual	deliv-
       eries  to  the same destination;	with per-destination recipient limit >
       1, a destination	is a domain, otherwise it is a recipient.

       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.

       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 changes the meaning of the cor-
       responding per-destination concurrency limit from concurrency  per  do-
       main into concurrency per 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_minimum_delivery_slots (default: 3)
       How  many recipients a message must have	in order to invoke the Postfix
       queue manager's scheduling algorithm  at	 all.	Messages  which	 would
       never  accumulate  at  least  this many delivery	slots (subject to slot
       cost parameter as well) are never preempted.

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

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

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

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

       This feature is available in Postfix 2.0	and later.

       The template is subject to exactly one level of $name substitution:

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

       $client_address
	      The client IP address.

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

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

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

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

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

       $rbl_domain
	      The RBL domain where $rbl_what is	blacklisted.

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

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

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

       $recipient_domain
	      The recipient domain or empty string.

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

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

       $sender_domain
	      The sender domain	or empty string.

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

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

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

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

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

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

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

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

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

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

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

       This feature is available in Postfix 2.4	and later.

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

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

       This feature is available in Postfix 2.4	and later.

default_transport (default: smtp)
       The default mail	delivery transport and next-hop	destination for	desti-
       nations that do not match $mydestination, $inet_interfaces,  $proxy_in-
       terfaces,  $virtual_alias_domains,  $virtual_mailbox_domains,  or  $re-
       lay_domains.  In	order of decreasing precedence,	the  nexthop  destina-
       tion   is   taken   from	 $default_transport,  $sender_dependent_relay-
       host_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
       part is optional.  For more details see the transport(5)	manual page.

       Example:

       default_transport = uucp:relayhostname

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

       This feature is available in Postfix 1.1	and later.

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

       Do  not	change	this  unless  you have a complete understanding	of RFC
       2821.

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 TLS

       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.

       This feature is enabled with the	delay_warning_time parameter.

delay_warning_time (default: 0h)
       The  time  after	 which the sender receives 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).

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.

       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

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

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

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

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

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

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

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

enable_original_recipient (default: yes)
       Enable support for the X-Original-To message  header.  This  header  is
       needed for multi-recipient mailboxes.

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

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

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

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

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

       This feature is available in Postfix 2.0	and later.

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

       This feature is available in Postfix 2.2	and later.

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

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

       Specify	a  list	 of names and/or name=value pairs, separated by	white-
       space or	comma. The name=value form is supported	with  Postfix  version
       2.1 and later.

       Example:

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

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

       This feature was	removed	in Postfix version 2.1.

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

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

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

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

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

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

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

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

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

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

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

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

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

       This feature is available in Postfix 2.3	and later.

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

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

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

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

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

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

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

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

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

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

       This feature is available in Postfix 2.0	and later.

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

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

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

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

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

       The  following  $name  expansions  are  done on forward_path before the
       search actually happens.	The result of $name expansion is filtered with
       the  character  set that	is specified with the forward_expansion_filter
       parameter.

       $user  The recipient's username.

       $shell The recipient's login shell pathname.

       $home  The recipient's home directory.

       $recipient
	      The full recipient address.

       $extension
	      The optional recipient address extension.

       $domain
	      The recipient domain.

       $local The entire recipient localpart.

       $recipient_delimiter
	      The system-wide recipient	address	extension delimiter.

       ${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.

       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 SMTP server	process	limit,	"in_flow_delay	=  1s"
       limits  the  mail inflow	to 100 messages	per second above the number of
       messages	delivered per second.

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

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

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

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

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

       On a multi-homed	firewall with separate Postfix instances listening  on
       the  "inside"  and "outside" interfaces,	this can prevent each instance
       from being able to reach	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 problem 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: ipv4)
       The  Internet  protocols	Postfix	will attempt to	use when making	or ac-
       cepting connections. Specify one	or more	of "ipv4" or "ipv6", separated
       by  whitespace  or commas. The form "all" is equivalent to "ipv4, ipv6"
       or "ipv4", depending on whether the operating system implements IPv6.

       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 to DNS type	A record lookups, 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 attempt to connect via IPv6	before attempting to use IPv4.

       Examples:

       inet_protocols =	ipv4 (DEFAULT)
       inet_protocols =	all
       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
       2821.

ipc_idle (default: version dependent)
       The  time  after	 which	a client closes	an idle	internal communication
       channel.	 The purpose is	to allow servers to terminate voluntarily  af-
       ter they	become idle. This is used, for example,	by the address resolv-
       ing 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 servers to terminate voluntarily  af-
       ter reaching their client limit.	 This is used, for example, by the ad-
       dress 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.

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

       This feature is available in Postfix 2.3	and later.

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

       This feature is available in Postfix 2.3	and later.

lmtp_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.

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

       o      The LMTP client idle time	limit is reached.  This	limit is spec-
	      ified 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 LMTP server as-
	      sociated with the	current	session	does not respond to  the  RSET
	      command.

       Most  of	 these	limitations will be removed after Postfix implements 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  LMTP  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 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_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  LMTP client	time limit for sending the LMTP	".", and for receiving
       the 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 LMTP	client time limit for sending the LMTP DATA command,  and  for
       receiving the 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 LMTP	client time limit for sending the LMTP message content.	  When
       the  connection	stalls	for more than $lmtp_data_xfer_timeout the LMTP
       client terminates the transfer.

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

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

       This feature is available in Postfix 2.3	and later.

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

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

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

lmtp_discard_lhlo_keyword_address_maps (default: empty)
       Lookup tables, indexed by the remote LMTP server	address, with case in-
       sensitive  lists	 of  LHLO  keywords (pipelining, starttls, auth, etc.)
       that the	LMTP client will ignore	in the LHLO  response  from  a	remote
       LMTP  server.  See lmtp_discard_lhlo_keywords for details. The table is
       not indexed by hostname for  consistency	 with  smtpd_discard_ehlo_key-
       word_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 LMTP client will ignore in the LHLO response from	a  re-
       mote 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_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_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  LMTP  client  time limit for sending the LHLO command, and for re-
       ceiving the initial 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 LMTP	client time limit for sending the MAIL FROM command,  and  for
       receiving the server response.

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

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

       This feature is available in Postfix 2.3	and later.

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

       This feature is available in Postfix 2.4	and later.

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

       This feature is available in Postfix 2.3	and later.

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

       This feature is available in Postfix 2.4	and later.

lmtp_quit_timeout (default: 300s)
       The LMTP	client time limit for sending the QUIT command,	 and  for  re-
       ceiving the 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 LMTP	client time limit for sending the RCPT TO command, and for re-
       ceiving the server response.

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

lmtp_rset_timeout (default: 20s)
       The LMTP	client time limit for sending the RSET command,	 and  for  re-
       ceiving	the  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	LMTP client lookup tables with one username:password entry per
       host  or	 domain.   If a	remote host or domain has no username:password
       entry, then the Postfix LMTP client will	not attempt to authenticate to
       the remote host.

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

       This feature is available in Postfix 2.3	and later.

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

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

       noplaintext
	      Disallow authentication methods that use plaintext passwords.

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

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

       noanonymous
	      Disallow anonymous logins.

       Example:

       lmtp_sasl_security_options = noplaintext

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

       This feature is available in Postfix 2.3	and later.

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

       This feature is available in Postfix 2.3	and later.

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

       This feature is available in Postfix 2.3	and later.

lmtp_send_xforward_command (default: no)
       Send  an	 XFORWARD command to the 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	supports  this
       command.

       This feature is available in Postfix 2.1	and later.

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

       This feature is available in Postfix 2.3	and later.

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

       This feature is available in Postfix 2.3	and later.

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

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

       This feature is available in Postfix 2.3	and later.

lmtp_tcp_port (default:	24)
       The default TCP port that the Postfix LMTP client connects to.

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

       This feature is available in Postfix 2.3	and later.

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

       This feature is available in Postfix 2.6	and later.

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

       This feature is available in Postfix 2.3	and later.

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

       This feature is available in Postfix 2.3	and later.

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

       This  feature  is  available  in	Postfix	2.6 and	later, when Postfix is
       compiled	and linked with	OpenSSL	0.9.9 or later.

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

       This  feature  is  available  in	Postfix	2.6 and	later, when Postfix is
       compiled	and linked with	OpenSSL	0.9.9 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_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: empty)
       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: SSLv3, TLSv1)
       The LMTP-specific version of the	smtp_tls_mandatory_protocols  configu-
       ration parameter. See there for details.

       This feature is available in Postfix 2.3	and later.

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

       This feature is available in Postfix 2.3	and later.

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

       This feature is available in Postfix 2.3	and later.

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

       This feature is available in Postfix 2.3	and later.

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

       This feature is available in Postfix 2.6	and later.

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

       This feature is available in Postfix 2.3	and later.

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

       This feature is available in Postfix 2.3	and later.

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

       This feature is available in Postfix 2.3	and later.

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

       This feature is available in Postfix 2.3	and later.

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

       This feature is available in Postfix 2.3	and later.

lmtp_tls_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 LMTP	client time limit for sending the XFORWARD  command,  and  for
       receiving the 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 /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_destination_concurrency_limit (default: 2)
       The  maximal  number of parallel	deliveries via the local mail delivery
       transport  to  the  same	 recipient  (when   "local_destination_recipi-
       ent_limit  =  1")  or  the maximal number of parallel deliveries	to the
       same local domain (when "local_destination_recipient_limit > 1").  This
       limit  is enforced by the queue manager.	The message delivery transport
       name is the first field in the entry in the master.cf file.

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

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

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

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

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

       Specify a list of zero or more of the following:

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

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

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

       permit_tls_clientcerts
	      Append the domain	name in	$myorigin or $mydomain when the	client
	      TLS  certificate	fingerprint  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	client
	      TLS  certificate is successfully verified, regardless of whether
	      it is listed on the server, and regardless of the	certifying au-
	      thority.

       check_address_map type:table

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

       Examples:

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

	   local_header_rewrite_clients	= static:all

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

	   local_header_rewrite_clients	= permit_inet_interfaces

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

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

	   local_header_rewrite_clients	= permit_mynetworks,
	       permit_sasl_authenticated permit_tls_clientcerts
	       check_address_map hash:/usr/local/etc/postfix/pop-before-smtp

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

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

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

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

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

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

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

       Details are described in	the LOCAL_RECIPIENT_README file.

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

       Examples:

       local_recipient_maps =

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

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

       Specify	a string of the	form transport:nexthop,	where transport	is the
       name of a mail delivery transport defined in master.cf.	 The  :nexthop
       part is optional.  For more details see the transport(5)	manual page.

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

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

       The following $name expansions are done on luser_relay:

       $domain
	      The recipient domain.

       $extension
	      The recipient address extension.

       $home  The recipient's home directory.

       $local The entire recipient address localpart.

       $recipient
	      The full recipient address.

       $recipient_delimiter
	      The system-wide recipient	address	extension delimiter.

       $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 a user account that does not
       share a group with other	accounts and that owns no other	files or  pro-
       cesses  on  the system.	In particular, don't specify nobody or daemon.
       PLEASE USE A DEDICATED USER ID AND GROUP	ID.

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

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

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

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

       Examples:

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

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

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

       The following environment variables are exported	to the command:

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

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

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

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

       DOMAIN The domain part of the recipient address.

       EXTENSION
	      The optional address extension.

       HOME   The recipient home directory.

       LOCAL  The recipient address localpart.

       LOGNAME
	      The recipient's username.

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

       RECIPIENT
	      The full recipient address.

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

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

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

       SENDER The full sender address.

       SHELL  The recipient's login shell.

       USER   The recipient username.

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

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

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

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

       Examples:

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

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

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

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

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

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

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

mailbox_size_limit (default: 51200000)
       The maximal size	of any local(8)	individual mailbox or maildir file, or
       zero (no	limit).	 In fact, this limits the size of  any	file  that  is
       written	to  upon  local	 delivery, including files written by external
       commands	that are executed by the local(8) delivery agent.

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

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

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

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

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

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

       This feature is available in Postfix 2.3	and later.

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

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

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

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

       Do not change this unless you have  a  complete	understanding  of  RFC
       2821.

masquerade_classes (default: envelope_sender, header_sender, header_recipient)

       What addresses are subject to address masquerading.

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

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

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

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

	   masquerade_domains =	foo.example.com	example.com

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

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

	   masquerade_domains =	!foo.example.com example.com

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

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

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

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

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

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

       Example:

       masquerade_domains = $mydomain

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

       By default, address masquerading	makes no exceptions.

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

       Examples:

       masquerade_exceptions = root, mailer-daemon
       masquerade_exceptions = root

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

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

       Examples:

       # 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)
       The maximal time	a message is queued before it is sent back as undeliv-
       erable.

       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 \\.

       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 \\.

       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_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: 2)
       The mail	filter protocol	version	and optional protocol  extensions  for
       communication  with  a  Milter (mail filter) application. Postfix sends
       this version number during the initial protocol handshake.   It	should
       match  the  version number that is expected by the mail filter applica-
       tion (or	by its Milter library).

       Protocol	versions:

       2      Use Sendmail 8 mail filter protocol version  2  (default	as  of
	      Sendmail version 8.11).

       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 as of
	      Sendmail version 8.14).

       Protocol	extensions:

       no_header_reply
	      Specify this when	the Milter application will not	reply for each
	      individual message header.

       This feature is available in Postfix 2.3	and later.

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

       This feature is available in Postfix 2.3	and later.

milter_unknown_command_macros (default:	see postconf -d	output)
       The  macros  that  are sent to version 3	or higher Milter (mail filter)
       applications after an unknown SMTP command.  See	 MILTER_README	for  a
       list of available macro names and their meanings.

       This feature is available in Postfix 2.3	and later.

mime_boundary_length_limit (default: 2048)
       The maximal length of MIME multipart boundary strings. The MIME proces-
       sor is unable to	distinguish between boundary strings that do not  dif-
       fer in the first	$mime_boundary_length_limit characters.

       This feature is available in Postfix 2.0	and later.

mime_header_checks (default: $header_checks)
       Optional	 lookup	 tables	for content inspection of MIME related message
       headers,	as described in	the header_checks(5) manual page.

       This feature is available in Postfix 2.0	and later.

mime_nesting_limit (default: 100)
       The maximal recursion level that	the MIME processor will	handle.	 Post-
       fix refuses mail	that is	nested deeper than the specified limit.

       This feature is available in Postfix 2.0	and later.

minimal_backoff_time (default: 300s)
       The  minimal time between attempts to deliver a deferred	message; prior
       to Postfix 2.4 the default value	was 1000s.

       This parameter also limits the time an unreachable destination is  kept
       in the short-term, in-memory, destination status	cache.

       This parameter should be	set greater than or equal to $queue_run_delay.
       See also	$maximal_backoff_time.

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

multi_instance_directories (default: empty)
       An  optional  list  of  non-default  Postfix configuration directories;
       these directories belong	to additional Postfix instances	that share the
       Postfix executable files	and documentation with the default Postfix in-
       stance, and that	are started, stopped, etc., together with the  default
       Postfix	instance.   Specify  a list of pathnames separated by comma or
       whitespace.

       When the	list of	non-default Postfix configuration directories is  non-
       empty,  the  postfix(1)	command	will invoke the	multi-instance manager
       specified with the multi_instance_wrapper parameter to execute commands
       on the default instance and on all additional Postfix instances.

       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
       2821.

       This feature is available in Postfix 2.1	and later.

mydestination (default:	$myhostname, localhost.$mydomain, localhost)
       The list	of domains that	are delivered via  the	$local_transport  mail
       delivery	 transport.  By	 default this is the Postfix local(8) delivery
       agent which looks up all	recipients in  /etc/passwd  and	 /etc/aliases.
       The  SMTP  server  validates  recipient	addresses  with	$local_recipi-
       ent_maps	and rejects non-existent recipients. See also the local	domain
       class in	the ADDRESS_CLASS_README file.

       The  default  mydestination value specifies names for the local machine
       only.  On a mail	domain gateway,	you should also	include	$mydomain.

       The $local_transport delivery method is	also  selected	for  mail  ad-
       dressed	to  user@[the.net.work.address]	of the mail system (the	IP ad-
       dresses specified with the inet_interfaces and proxy_interfaces parame-
       ters).

       Warnings:

       o      Do  not specify the names	of virtual domains - those domains are
	      specified	elsewhere. See VIRTUAL_README for more information.

       o      Do not specify the names of domains that this machine is	backup
	      MX host for. See STANDARD_CONFIGURATION_README for how to	set up
	      backup MX	hosts.

       o      By default, the Postfix SMTP server rejects mail for  recipients
	      not  listed  with	 the  local_recipient_maps parameter.  See the
	      postconf(5) manual for a description of the local_recipient_maps
	      and unknown_local_recipient_reject_code parameters.

       Specify	a  list	 of host or domain names, "/file/name" or "type:table"
       patterns, separated by commas and/or whitespace.	A "/file/name" pattern
       is  replaced  by	 its  contents;	a "type:table" lookup table is matched
       when a name matches a lookup key	(the lookup result is ignored).	  Con-
       tinue long lines	by starting the	next line with whitespace.

       Examples:

       mydestination = $myhostname, localhost.$mydomain	$mydomain
       mydestination = $myhostname, localhost.$mydomain	www.$mydomain, ftp.$mydomain

mydomain (default: see postconf	-d output)
       The  internet  domain  name of this mail	system.	 The default is	to use
       $myhostname minus the first component.  $mydomain is used as a  default
       value for many other configuration 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 from	gethostname(). $myhostname is used  as
       a default value for many	other configuration parameters.

       Example:

       myhostname = host.domain.tld

mynetworks (default: see postconf -d output)
       The  list  of  "trusted"	 SMTP  clients	that have more privileges than
       "strangers".

       In particular, "trusted"	SMTP clients are allowed to relay mail through
       Postfix.	 See the smtpd_recipient_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:/usr/local/etc/postfix/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"
	      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"
	      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".	See the	MILTER_README document for details.

       This feature is available in Postfix 2.3	and later.

notify_classes (default: resource, software)
       The  list of error classes that are reported to the postmaster. The de-
       fault is	to report only the most	serious	 problems.  The	 paranoid  may
       wish  to	 turn on the policy (UCE and mail relaying) and	protocol error
       (broken mail software) reports.

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

       The error classes are:

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

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

       delay  Send the postmaster copies of the	headers	of delayed  mail.  The
	      notification is sent to the address specified with the delay_no-
	      tice_recipient configuration parameter (default: postmaster).

       policy Send the postmaster a transcript of  the	SMTP  session  when  a
	      client request was rejected because of (UCE) policy. The notifi-
	      cation is	sent to	 the  address  specified  with	the  error_no-
	      tice_recipient configuration parameter (default: postmaster).

       protocol
	      Send  the	postmaster a transcript	of the SMTP session in case of
	      client or	server protocol	errors.	The notification  is  sent  to
	      the address specified with the error_notice_recipient configura-
	      tion parameter (default: postmaster).

       resource
	      Inform the postmaster of mail  not  delivered  due  to  resource
	      problems.	  The  notification  is	 sent to the address specified
	      with the	error_notice_recipient	configuration  parameter  (de-
	      fault: postmaster).

       software
	      Inform  the  postmaster  of  mail	 not delivered due to software
	      problems.	 The notification is sent  to  the  address  specified
	      with  the	 error_notice_recipient	 configuration	parameter (de-
	      fault: postmaster).

       Examples:

       notify_classes =	bounce,	delay, policy, protocol, resource, software
       notify_classes =	2bounce, resource, software

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

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

permit_mx_backup_networks (default: empty)
       Restrict	the use	of the permit_mx_backup	SMTP access  feature  to  only
       domains	whose primary MX hosts match the listed	networks.  The parame-
       ter value syntax	is the same as with the	 mynetworks  parameter;	 note,
       however,	that the default value is empty.

pickup_service_name (default: pickup)
       The  name  of  the  pickup(8) service. This service picks up local mail
       submissions from	the Postfix maildrop queue.

       This feature is available in Postfix 2.0	and later.

plaintext_reject_code (default:	450)
       The numerical Postfix SMTP server response code when a request  is  re-
       jected by the reject_plaintext_session restriction.

       This feature is available in Postfix 2.3	and later.

prepend_delivered_header (default: command, file, forward)
       The message delivery contexts where the Postfix local(8)	delivery agent
       prepends	a Delivered-To:	 message header	with the address that the mail
       was  delivered  to. This	information is used for	mail delivery loop de-
       tection.

       By default, the Postfix local delivery agent prepends  a	 Delivered-To:
       header  when  forwarding	mail and when delivering to file (mailbox) and
       command.	Turning	off the	Delivered-To: header when forwarding  mail  is
       not recommended.

       Specify zero or more of forward,	file, or command.

       Example:

       prepend_delivered_header	= forward

process_id (read-only)
       The process ID of a Postfix command or daemon process.

process_id_directory (default: pid)
       The  location  of Postfix PID files relative to $queue_directory.  This
       is a read-only parameter.

process_name (read-only)
       The process name	of a Postfix command or	daemon process.

propagate_unmatched_extensions (default: canonical, virtual)
       What address lookup tables copy an address extension  from  the	lookup
       key to the lookup result.

       For   example,	with  a	 virtual(5)  mapping  of  "joe@example.com  =_
       joe.user@example.net", the address "joe+foo@example.com"	would  rewrite
       to "joe.user+foo@example.net".

       Specify	zero or	more of	canonical, virtual, alias, forward, include or
       generic.	These cause address extension propagation  with	 canonical(5),
       virtual(5),  and	 aliases(5) maps, with local(8)	.forward and :include:
       file lookups, and with smtp(8) generic maps, respectively.

       Note: enabling this feature for types other than	canonical and  virtual
       is  likely to cause problems when mail is forwarded to other sites, es-
       pecially	with mail that is sent to a mailing list exploder address.

       Examples:

       propagate_unmatched_extensions =	canonical, virtual, alias,
	       forward,	include
       propagate_unmatched_extensions =	canonical, virtual

proxy_interfaces (default: empty)
       The network interface addresses that this mail system receives mail  on
       by way of a proxy or network address translation	unit.

       This feature is available in Postfix 2.0	and later.

       You must	specify	your "outside" proxy/NAT addresses when	your system is
       a backup	MX host	for other domains, otherwise mail delivery loops  will
       happen when the primary MX host is down.

       Example:

       proxy_interfaces	= 1.2.3.4

proxy_read_maps	(default: see postconf -d output)
       The  lookup tables that the proxymap(8) server is allowed to access for
       the read-only service.  Table references	that don't begin  with	proxy:
       are ignored.

       This feature is available in Postfix 2.0	and later.

proxy_write_maps (default: see postconf	-d output)
       The  lookup tables that the proxymap(8) server is allowed to access for
       the read-write service. Postfix-owned local database  files  should  be
       stored  under  the Postfix-owned	data_directory.	 Table references that
       don't begin with	proxy: are ignored.

       This feature is available in Postfix 2.5	and later.

proxymap_service_name (default:	proxymap)
       The name	of the proxymap	read-only table	lookup service.	 This  service
       is normally implemented by the proxymap(8) daemon.

       This feature is available in Postfix 2.6	and later.

proxywrite_service_name	(default: proxywrite)
       The  name of the	proxywrite read-write table lookup service.  This ser-
       vice is normally	implemented by the proxymap(8) daemon.

       This feature is available in Postfix 2.6	and later.

qmgr_clog_warn_time (default: 300s)
       The minimal delay between warnings that a specific destination is clog-
       ging up the Postfix active queue. Specify 0 to disable.

       This feature is enabled with the	helpful_warnings parameter.

       This feature is available in Postfix 2.0	and later.

qmgr_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_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 size of the	short-term,  in-memory
       "dead" destination 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 clients are	allowed	to connect to the 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 QMQP server will pause before sending a negative reply to
       the 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	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 SMTP	server
       to decide if it will accept any mail at all.

       By default, the Postfix version 2.1 SMTP	server rejects MAIL FROM  com-
       mands   when   the   amount  of	free  space  is	 less  than  1.5*$mes-
       sage_size_limit.	 To specify a higher minimum free space	limit, specify
       a queue_minfree value that is at	least 1.5*$message_size_limit.

       With  Postfix  versions	2.0 and	earlier, a queue_minfree value of zero
       means there is no minimum required amount of free space.

queue_run_delay	(default: 300s)
       The time	between	deferred queue scans by	the queue  manager;  prior  to
       Postfix 2.4 the default value was 1000s.

       This  parameter	should	be  set	 less  than or equal to	$minimal_back-
       off_time. See also $maximal_backoff_time.

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

queue_service_name (default: qmgr)
       The name	of the qmgr(8) service.	This service manages the Postfix queue
       and schedules delivery requests.

       This feature is available in Postfix 2.0	and later.

rbl_reply_maps (default: empty)
       Optional	lookup tables with RBL response	templates. The tables are  in-
       dexed by	the RBL	domain name. By	default, Postfix uses the default tem-
       plate as	specified with the default_rbl_reply configuration  parameter.
       See there for a discussion of the syntax	of RBL reply templates.

       This feature is available in Postfix 2.0	and later.

readme_directory (default: see postconf	-d output)
       The  location  of Postfix README	files that describe how	to build, con-
       figure or operate a specific Postfix subsystem or feature.

receive_override_options (default: empty)
       Enable or disable recipient validation, built-in	content	filtering,  or
       address	mapping.  Typically,  these are	specified in master.cf as com-
       mand-line arguments for the smtpd(8), qmqpd(8) or pickup(8) daemons.

       Specify zero or more of the following options.	The  options  override
       main.cf	settings  and are either implemented by	smtpd(8), qmqpd(8), or
       pickup(8) themselves, or	they are forwarded to the cleanup server.

       no_unknown_recipient_checks
	      Do not try to reject  unknown  recipients	 (SMTP	server	only).
	      This is typically	specified AFTER	an external content filter.

       no_address_mappings
	      Disable  canonical address mapping, virtual alias	map expansion,
	      address masquerading, and	automatic BCC (blind carbon-copy)  re-
	      cipients.	This is	typically specified BEFORE an external content
	      filter.

       no_header_body_checks
	      Disable header/body_checks. This is typically specified AFTER an
	      external content filter.

       no_milters
	      Disable  Milter  (mail  filter)  applications. This is typically
	      specified	AFTER an external content filter.

       Note: when the "BEFORE content filter" receive_override_options setting
       is  specified  in  the main.cf file, specify the	"AFTER content filter"
       receive_override_options	setting	in master.cf (and vice versa).

       Examples:

       receive_override_options	=
	   no_unknown_recipient_checks,	no_header_body_checks
       receive_override_options	= no_address_mappings

       This feature is available in Postfix 2.1	and later.

recipient_bcc_maps (default: empty)
       Optional	BCC (blind carbon-copy)	address	lookup tables, indexed by  re-
       cipient	address.  The BCC address (multiple results are	not supported)
       is added	when mail enters from outside of Postfix.

       This feature is available in Postfix 2.1	and later.

       The table search	order is as follows:

       o      Look up the "user+extension@domain.tld"  address	including  the
	      optional address extension.

       o      Look  up	the "user@domain.tld" address without the optional ad-
	      dress extension.

       o      Look up the "user+extension" address local part when the recipi-
	      ent domain equals	$myorigin, $mydestination, $inet_interfaces or
	      $proxy_interfaces.

       o      Look up the "user" address local part when the recipient	domain
	      equals $myorigin,	$mydestination,	$inet_interfaces or $proxy_in-
	      terfaces.

       o      Look up the "@domain.tld"	part.

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

       Note:  if  mail	to  the	BCC address bounces it will be returned	to the
       sender.

       Note: automatic BCC recipients are produced  only  for  new  mail.   To
       avoid mailer loops, automatic BCC recipients are	not generated for mail
       that Postfix forwards internally, nor for mail that  Postfix  generates
       itself.

       Example:

       recipient_bcc_maps = hash:/usr/local/etc/postfix/recipient_bcc

recipient_canonical_classes (default: envelope_recipient, header_recipient)
       What addresses are subject to recipient_canonical_maps address mapping.
       By default, recipient_canonical_maps address mapping is applied to  en-
       velope recipient	addresses, and to header recipient addresses.

       Specify one or more of: envelope_recipient, header_recipient

       This feature is available in Postfix 2.2	and later.

recipient_canonical_maps (default: empty)
       Optional	 address mapping lookup	tables for envelope and	header recipi-
       ent addresses.  The table format	and lookups are	documented in  canoni-
       cal(5).

       Note: $recipient_canonical_maps is processed before $canonical_maps.

       Example:

       recipient_canonical_maps	= hash:/usr/local/etc/postfix/recipient_canonical

recipient_delimiter (default: empty)
       The  separator  between	user  names and	address	extensions (user+foo).
       See canonical(5), local(8), relocated(5)	and virtual(5) for the effects
       this has	on aliases, canonical, virtual,	relocated and on .forward file
       lookups.	 Basically, the	software tries user+foo	and  .forward+foo  be-
       fore trying user	and .forward.

       Example:

       recipient_delimiter = +

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
       2821.

reject_tempfail_action (default: defer_if_permit)
       The  Postfix  SMTP server's action when a reject-type restriction fails
       due to a	temporary error	condition. Specify "defer" to defer the	remote
       SMTP client request immediately.	With the default "defer_if_permit" ac-
       tion, the Postfix SMTP server continues to look	for  opportunities  to
       reject  mail,  and defers the client request only if it would otherwise
       be accepted.

       For finer control, see:	unverified_recipient_tempfail_action,  unveri-
       fied_sender_tempfail_action,  unknown_address_tempfail_action,  and un-
       known_helo_hostname_tempfail_action.

       This feature is available in Postfix 2.6	and later.

relay_clientcerts (default: empty)
       List of tables with remote  SMTP	 client-certificate  fingerprints  for
       which  the  Postfix  SMTP  server  will	allow  access  with  the  per-
       mit_tls_clientcerts feature.  The fingerprint digest algorithm is  con-
       figurable via the smtpd_tls_fingerprint_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:/usr/local/etc/postfix/relay_clientcerts

       For  more fine-grained control, use check_ccert_access to select	an ap-
       propriate   access(5)   policy	for   each   client.	See   RESTRIC-
       TION_CLASS_README.

       This feature is available with Postfix version 2.2.

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

       This feature is available in Postfix 2.0	and later.

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

       Setting	this  parameter	 to  a	value  of 1 changes the	meaning	of re-
       lay_destination_concurrency_limit from concurrency per domain into con-
       currency	per recipient.

       This feature is available in Postfix 2.0	and later.

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

       Domains	that match $relay_domains are delivered	with the $relay_trans-
       port mail delivery transport. The SMTP server validates	recipient  ad-
       dresses with $relay_recipient_maps and rejects non-existent recipients.
       See also	the relay domains address class	 in  the  ADDRESS_CLASS_README
       file.

       Note: Postfix will not automatically forward mail for domains that list
       this  system  as	 their	primary	 or  backup  MX	 host.	See  the  per-
       mit_mx_backup restriction in the	postconf(5) manual page.

       Specify	a  list	 of  host  or  domain  names, "/file/name" patterns or
       "type:table" lookup tables,  separated  by  commas  and/or  whitespace.
       Continue	 long  lines  by  starting  the	 next  line with whitespace. A
       "/file/name" pattern is replaced	by its contents; a "type:table"	lookup
       table  is matched when a	(parent) domain	appears	as lookup key. Specify
       "!pattern" to exclude a domain from the list. The form "!/file/name" is
       supported only in Postfix version 2.4 and later.

relay_domains_reject_code (default: 554)
       The  numerical  Postfix SMTP server response code when a	client request
       is rejected by the reject_unauth_destination recipient restriction.

       Do not change this unless you have  a  complete	understanding  of  RFC
       2821.

relay_recipient_maps (default: empty)
       Optional	 lookup	 tables	 with  all valid addresses in the domains that
       match $relay_domains. Specify @domain as	a wild-card for	 domains  that
       have  no	valid recipient	list, and become a source of backscatter mail:
       Postfix accepts spam for	non-existent recipients	and then floods	 inno-
       cent  people  with undeliverable	mail.  Technically, tables listed with
       $relay_recipient_maps are used as lists:	Postfix	needs to know only  if
       a  lookup  string  is found or not, but it does not use the result from
       table lookup.

       If this parameter is non-empty, then the	Postfix	SMTP server  will  re-
       ject mail to unknown relay users. This feature is off by	default.

       See  also  the  relay domains address class in the ADDRESS_CLASS_README
       file.

       Example:

       relay_recipient_maps = hash:/usr/local/etc/postfix/relay_recipients

       This feature is available in Postfix 2.0	and later.

relay_transport	(default: relay)
       The default mail	delivery transport and next-hop	destination for	remote
       delivery	 to domains listed with	$relay_domains.	In order of decreasing
       precedence, the nexthop destination  is	taken  from  $relay_transport,
       $sender_dependent_relayhost_maps, $relayhost, or	from the recipient do-
       main. This information can be overruled with the	transport(5) table.

       Specify a string	of the form transport:nexthop, where transport is  the
       name  of	 a mail	delivery transport defined in master.cf.  The :nexthop
       part is optional.  For more details see the transport(5)	manual page.

       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,  default_transport,  sender_dependent_relayhost_maps and with the
       transport(5) table.

       On an intranet, specify the organizational domain name. If your	inter-
       nal  DNS	 uses  no MX records, specify the name of the intranet gateway
       host instead.

       In the case of SMTP, specify a domain  name,  hostname,	hostname:port,
       [hostname]:port,	 [hostaddress]	or [hostaddress]:port. The form	[host-
       name] turns off MX lookups.

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

       Examples:

       relayhost = $mydomain
       relayhost = [gateway.my.domain]
       relayhost = uucphost
       relayhost = [an.ip.add.ress]

relocated_maps (default: empty)
       Optional	 lookup	 tables	 with new contact information for users	or do-
       mains that no longer exist.  The	table format  and  lookups  are	 docu-
       mented in relocated(5).

       If you use this feature,	run "postmap /usr/local/etc/postfix/relocated"
       to build	the necessary DBM or  DB  file	after  change,	then  "postfix
       reload" to make the changes visible.

       Examples:

       relocated_maps =	dbm:/usr/local/etc/postfix/relocated
       relocated_maps =	hash:/usr/local/etc/postfix/relocated

remote_header_rewrite_domain (default: empty)
       Don't  rewrite message headers from remote clients at all when this pa-
       rameter is empty; otherwise, rewrite message  headers  and  append  the
       specified  domain  name	to incomplete addresses.  The local_header_re-
       write_clients parameter controls	what clients Postfix considers local.

       Examples:

       The safe	setting: append	 "domain.invalid"  to  incomplete  header  ad-
       dresses	from  remote  SMTP  clients, so	that those addresses cannot be
       confused	with local addresses.

	   remote_header_rewrite_domain	= domain.invalid

       The default, purist, setting: don't rewrite headers from	remote clients
       at all.

	   remote_header_rewrite_domain	=

require_home_directory (default: no)
       Whether	or not a local(8) recipient's home directory must exist	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 (NOT RECOMMENDED).

resolve_dequoted_address (default: yes)
       Resolve a recipient address safely instead of correctly,	by looking in-
       side quotes.

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

       If you specify "resolve_dequoted_address	= no", then  the  Postfix  re-
       solver  will  not know about additional @ etc. operators	in the address
       localpart. This opens opportunities for obscure mail relay attacks with
       user@domain@domain  addresses  when  Postfix provides backup MX service
       for Sendmail systems.

resolve_null_domain (default: no)
       Resolve an address that ends in the "@" null domain  as	if  the	 local
       hostname	were specified,	instead	of rejecting the address as invalid.

       This  feature  is available in Postfix 2.1 and later.  Earlier versions
       always resolve the null domain as the local hostname.

       The Postfix SMTP	server uses this feature to reject mail	from or	to ad-
       dresses	that  end  in the "@" null domain, and from addresses that re-
       write into a form that ends in the "@" null domain.

resolve_numeric_domain (default: no)
       Resolve "user@ipaddress"	as "user@[ipaddress]",	instead	 of  rejecting
       the address as invalid.

       This feature is available in Postfix 2.3	and later.

rewrite_service_name (default: rewrite)
       The  name  of  the address rewriting service. This service rewrites ad-
       dresses to standard form	and resolves them to a (delivery method, next-
       hop host, recipient) triple.

       This feature is available in Postfix 2.0	and later.

sample_directory (default: /usr/local/etc/postfix)
       The name	of the directory with example Postfix configuration files.

send_cyrus_sasl_authzid	(default: no)
       When  authenticating  to	 a remote SMTP or LMTP server with the default
       setting "no", send no SASL authoriZation	ID (authzid);  send  only  the
       SASL authentiCation ID (authcid)	plus the authcid's password.

       The  non-default	 setting  "yes"	 enables the behavior of older Postfix
       versions.  These	always send a SASL authzid that	is equal to  the  SASL
       authcid,	 but  this  causes  inter-operability  problems	with some SMTP
       servers.

       This feature is available in Postfix 2.4.4 and later.

sender_based_routing (default: no)
       This parameter should not be used. It  was  replaced  by	 sender_depen-
       dent_relayhost_maps in Postfix version 2.3.

sender_bcc_maps	(default: empty)
       Optional	 BCC  (blind  carbon-copy)  address  lookup tables, indexed by
       sender address.	The BCC	address	(multiple results are  not  supported)
       is added	when mail enters from outside of Postfix.

       This feature is available in Postfix 2.1	and later.

       The table search	order is as follows:

       o      Look  up	the  "user+extension@domain.tld" address including the
	      optional address extension.

       o      Look up the "user@domain.tld" address without the	 optional  ad-
	      dress extension.

       o      Look  up the "user+extension" address local part when the	sender
	      domain equals  $myorigin,	 $mydestination,  $inet_interfaces  or
	      $proxy_interfaces.

       o      Look  up	the  "user"  address local part	when the sender	domain
	      equals $myorigin,	$mydestination,	$inet_interfaces or $proxy_in-
	      terfaces.

       o      Look up the "@domain.tld"	part.

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

       Note: if	mail to	the BCC	address	bounces	it will	 be  returned  to  the
       sender.

       Note:  automatic	 BCC  recipients  are  produced	only for new mail.  To
       avoid mailer loops, automatic BCC recipients are	not generated for mail
       that  Postfix  forwards internally, nor for mail	that Postfix generates
       itself.

       Example:

       sender_bcc_maps = hash:/usr/local/etc/postfix/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:/usr/local/etc/postfix/sender_canonical

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,  default_transport  and  with
       the transport(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_path (default:	see postconf -d	output)
       A Sendmail compatibility	feature	that specifies	the  location  of  the
       Postfix	sendmail(1)  command.  This command can	be used	to submit mail
       into the	Postfix	queue.

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

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

setgid_group (default: postdrop)
       The group ownership of set-gid Postfix commands and  of	group-writable
       Postfix	directories.  When this	parameter value	is changed you need to
       re-run "postfix set-permissions"	(with Postfix version 2.0 and earlier:
       "/usr/local/etc/postfix/post-install set-permissions".

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

       This feature is available in Postfix 2.0	and later.

showq_service_name (default: showq)
       The name	of the showq(8)	service. This service produces mail queue sta-
       tus reports.

       This feature is available in Postfix 2.0	and later.

smtp_always_send_ehlo (default:	yes)
       Always send EHLO	at the start of	an SMTP	session.

       With "smtp_always_send_ehlo = no", Postfix sends	 EHLO  only  when  the
       word  "ESMTP"  appears  in  the	server	greeting  banner (example: 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)
       Allow DNS CNAME records to override the	servername  that  the  Postfix
       SMTP  client  uses  for logging,	SASL password lookup, TLS policy deci-
       sions, or TLS certificate verification. The value "no" hardens  Postfix
       smtp_tls_per_site hostname-based	policies against false hostname	infor-
       mation in DNS CNAME records, and	makes SASL password file lookups  more
       predictable. This is the	default	setting	as of Postfix 2.3.

       This feature is available in Postfix 2.2.9 and later.

smtp_connect_timeout (default: 30s)
       The  SMTP  client  time	limit for completing a TCP connection, or zero
       (use the	operating system built-in time limit).

       When no connection can be made within the deadline,  the	 Postfix  SMTP
       client  tries the next address on the mail exchanger list. Specify 0 to
       disable the time	limit (i.e. use	whatever timeout is implemented	by the
       operating system).

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

smtp_connection_cache_destinations (default: empty)
       Permanently enable SMTP connection caching for the  specified  destina-
       tions.	With SMTP connection caching, a	connection is not closed imme-
       diately after completion	of a mail transaction.	Instead,  the  connec-
       tion  is	kept open for up to $smtp_connection_cache_time_limit seconds.
       This allows connections to be reused for	other deliveries, and can  im-
       prove mail delivery performance.

       Specify	a  comma  or  white  space  separated  list of destinations or
       pseudo-destinations:

       o      if mail is sent without a	relay host: a domain name (the	right-
	      hand  side  of an	email address, without the [] around a numeric
	      IP address),

       o      if mail is sent via a relay host:	a relay	host name (without  []
	      or  non-default  TCP  port),  as	specified in main.cf or	in the
	      transport	map,

       o      if mail is sent via a UNIX-domain	socket:	 a  pathname  (without
	      the unix:	prefix),

       o      a	 /file/name  with  domain names	and/or relay host names	as de-
	      fined above,

       o      a	"type:table" with domain names and/or relay host names on  the
	      left-hand	 side.	 The  right-hand side result from "type:table"
	      lookups is ignored.

       This feature is available in Postfix 2.2	and later.

smtp_connection_cache_on_demand	(default: yes)
       Temporarily enable SMTP connection caching while	a  destination	has  a
       high volume of mail in the active queue.	 With SMTP connection caching,
       a connection is not closed  immediately	after  completion  of  a  mail
       transaction.  Instead, the connection is	kept open for up to $smtp_con-
       nection_cache_time_limit	seconds.  This allows connections to be	reused
       for other deliveries, and can improve mail delivery performance.

       This feature is available in Postfix 2.2	and later.

smtp_connection_cache_reuse_limit (default: 10)
       When  SMTP  connection  caching is enabled, the number of times that an
       SMTP session may	be reused before it is closed.

       This feature is available in Postfix 2.2. In Postfix 2.3	it is replaced
       by $smtp_connection_reuse_time_limit.

smtp_connection_cache_time_limit (default: 2s)
       When SMTP connection caching is enabled,	the amount of time that	an un-
       used SMTP client	socket is kept open before it is closed.  Do not spec-
       ify larger values without permission from the remote sites.

       This feature is available in Postfix 2.2	and later.

smtp_connection_reuse_time_limit (default: 300s)
       The amount of time during which Postfix will use	an SMTP	connection re-
       peatedly.  The timer starts when	the connection is initiated  (i.e.  it
       includes	the connect, greeting and helo latency,	in addition to the la-
       tencies of subsequent mail delivery transactions).

       This feature addresses a	performance stability problem with remote SMTP
       servers.	 This  problem	is not specific	to Postfix: it can happen when
       any MTA sends large amounts of SMTP email to a site that	 has  multiple
       MX hosts.

       The  problem  starts  when one of a set of MX hosts becomes slower than
       the rest.  Even though SMTP clients connect to fast and slow  MX	 hosts
       with equal probability, the slow	MX host	ends up	with more simultaneous
       inbound connections than	the faster MX hosts, because the slow MX  host
       needs more time to serve	each client request.

       The  slow  MX  host becomes a connection	attractor.  If one MX host be-
       comes N times slower than the rest, it dominates	mail delivery  latency
       unless  there  are more than N fast MX hosts to counter the effect. And
       if the number of	MX hosts is smaller than N, the	mail delivery  latency
       becomes	effectively  that  of the slowest MX host divided by the total
       number of MX hosts.

       The solution uses connection caching in a way that differs from Postfix
       version	2.2.  By limiting the amount of	time during which a connection
       can be used repeatedly (instead of limiting the	number	of  deliveries
       over  that  connection),	Postfix	not only restores fairness in the dis-
       tribution of simultaneous connections across a set of MX	hosts, it also
       favors  deliveries over connections that	perform	well, which is exactly
       what we want.

       The default reuse time limit, 300s, is comparable to the	 various  smtp
       transaction timeouts which are fair estimates of	maximum	excess latency
       for a slow delivery.  Note that hosts may accept	thousands of  messages
       over  a	single	connection  within  the	 default connection reuse time
       limit. This number is much larger than the default Postfix version  2.2
       limit  of  10 messages per cached connection. It	may prove necessary to
       lower the limit to avoid	interoperability issues	with MTAs that exhibit
       bugs when many messages are delivered via a single connection.  A lower
       reuse time limit	risks losing the benefit of connection reuse when  the
       average	connection  and	 mail  delivery	latency	exceeds	the reuse time
       limit.

       This feature is available in Postfix 2.3	and later.

smtp_data_done_timeout (default: 600s)
       The SMTP	client time limit for sending the SMTP ".", and	for  receiving
       the 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  SMTP  client time limit for	sending	the SMTP DATA command, and for
       receiving the 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  SMTP client	time limit for sending the SMTP	message	content.  When
       the connection makes no progress	for more than  $smtp_data_xfer_timeout
       seconds the Postfix SMTP	client terminates the transfer.

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

smtp_defer_if_no_mx_address_found (default: no)
       Defer mail delivery when	no MX record resolves to an IP address.

       The default (no)	is to return the mail  as  undeliverable.  With	 older
       Postfix versions	the default was	to keep	trying to deliver the mail un-
       til someone fixed the MX	record or until	the mail was too old.

       Note: Postfix always ignores MX records with equal or worse  preference
       than the	local MTA itself.

       This feature is available in Postfix 2.1	and later.

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

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

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

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

       This feature is available in Postfix 2.2	and later.

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

       This feature is available in Postfix 2.2	and later.

       Notes:

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

       o      Use  the	smtp_discard_ehlo_keyword_address_maps feature to dis-
	      card EHLO	keywords selectively.

smtp_enforce_tls (default: no)
       Enforcement mode: require that remote SMTP servers use TLS  encryption,
       and  never  send	mail in	the clear.  This also requires that the	remote
       SMTP server hostname matches the	information in the remote server  cer-
       tificate,  and  that the	remote SMTP server certificate was issued by a
       CA that is trusted by the  Postfix  SMTP	 client.  If  the  certificate
       doesn't	verify or the hostname doesn't match, delivery is deferred and
       mail stays in the queue.

       The server hostname is matched against all names	provided  as  dNSNames
       in  the SubjectAlternativeName.	If no dNSNames are specified, the Com-
       monName is checked.  The	behavior may be	changed	with the  smtp_tls_en-
       force_peername option.

       This  option  is	 useful	 only if you are definitely sure that you will
       only connect to servers that support RFC	2487 _and_ that	provide	 valid
       server  certificates.   Typical	use is for clients that	send all their
       email to	a dedicated mailhub.

       This feature is available in Postfix 2.2	and later.  With  Postfix  2.3
       and later use smtp_tls_security_level instead.

smtp_fallback_relay (default: $fallback_relay)
       Optional	 list of relay hosts for SMTP destinations that	can't be found
       or that are unreachable.	With Postfix 2.2 and earlier this parameter is
       called fallback_relay.

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

       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 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 SMTP	client time limit for sending the HELO or  EHLO	 command,  and
       for receiving the initial 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 when the	Postfix	SMTP client uses to look up  a	host's
       IP address.  This parameter is ignored when DNS lookups are disabled.

       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: 990)
       The maximal length of message header and	body lines that	 Postfix  will
       send via	SMTP.  Longer lines are	broken by inserting "<CR><LF><SPACE>".
       This minimizes the damage to MIME formatted mail.

       By default, the line length is limited to 990 characters, because  some
       server implementations cannot receive mail with long lines.

smtp_mail_timeout (default: 300s)
       The  SMTP  client time limit for	sending	the MAIL FROM command, and for
       receiving the 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 mail exchanger lookups, or zero (no	limit).	Prior to Postfix  ver-
       sion 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	giving
       up or delivering	to a fall-back relay host, or zero  (no	 limit).  This
       restriction  ignores  sessions  that  fail to complete the SMTP initial
       handshake (Postfix version 2.2 and earlier) or that  fail  to  complete
       the EHLO	and TLS	handshake (Postfix version 2.3 and later).

       This feature is available in Postfix 2.1	and later.

smtp_nested_header_checks (default: empty)
       Restricted  nested_header_checks(5) tables for the Postfix SMTP client.
       These tables are	searched while mail is being delivered.	 Actions  that
       change the delivery time	or destination are not available.

       This feature is available in Postfix 2.5	and later.

smtp_never_send_ehlo (default: no)
       Never  send EHLO	at the start of	an SMTP	session. See also the smtp_al-
       ways_send_ehlo parameter.

smtp_pix_workaround_delay_time (default: 10s)
       How long	the Postfix SMTP client	pauses before sending  ".<CR><LF>"  in
       order to	work around the	PIX firewall "<CR><LF>.<CR><LF>" bug.

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

smtp_pix_workaround_maps (default: empty)
       Lookup tables, indexed by the remote SMTP server	address, with per-des-
       tination	workarounds for	CISCO PIX firewall bugs.  The table is not in-
       dexed by	hostname for  consistency  with	 smtp_discard_ehlo_keyword_ad-
       dress_maps.

       This feature is available in Postfix 2.4	and later.

smtp_pix_workaround_threshold_time (default: 500s)
       How  long a message must	be queued before the Postfix SMTP client turns
       on the PIX firewall "<CR><LF>.<CR><LF>"	bug  workaround	 for  delivery
       through firewalls with "smtp fixup" mode	turned on.

       By  default,  the  workaround is	turned off for mail that is queued for
       less than 500 seconds. In  other	 words,	 the  workaround  is  normally
       turned off for the first	delivery attempt.

       Specify 0 to enable the PIX firewall "<CR><LF>.<CR><LF>"	bug workaround
       upon the	first delivery attempt.

smtp_pix_workarounds (default: disable_esmtp, delay_dotcrlf)
       A list that specifies zero or more workarounds for CISCO	 PIX  firewall
       bugs.  These  workarounds  are  implemented by the Postfix SMTP client.
       Workaround names	are separated by comma or space, and are case insensi-
       tive.   This  parameter	setting	 can be	overruled with per-destination
       smtp_pix_workaround_maps	settings.

       delay_dotcrlf
	      Insert a delay before sending ".<CR><LF>"	after the end  of  the
	      message  content.	  The  delay  is subject to the	smtp_pix_work-
	      around_delay_time	and smtp_pix_workaround_threshold_time parame-
	      ter settings.

       disable_esmtp
	      Disable all extended SMTP	commands: send HELO instead of EHLO.

       This  feature  is  available in Postfix 2.4 and later. The default set-
       tings are backwards compatible with earlier Postfix versions.

smtp_quit_timeout (default: 300s)
       The SMTP	client time limit for sending the QUIT command,	 and  for  re-
       ceiving the 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 SMTP MAIL FROM and RCPT TO commands as  required  by
       RFC 2821. This includes putting quotes around an	address	localpart that
       ends in ".".

       The default is to comply	with RFC 2821. 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  SMTP  client  time limit for sending the SMTP RCPT TO command, and
       for receiving the server	response.

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

smtp_rset_timeout (default: 20s)
       The  SMTP  client  time limit for sending the RSET command, and for re-
       ceiving the server response. The	SMTP client sends  RSET	 in  order  to
       finish a	recipient address probe, or to verify that a cached session is
       still usable.

       This feature is available in Postfix 2.1	and later.

smtp_sasl_auth_cache_name (default: empty)
       An optional table to prevent repeated SASL authentication failures with
       the same	remote SMTP server hostname, username and password. Each table
       (key, value) pair contains a server name, a username and	password,  and
       the full	server response. This information is stored when a remote SMTP
       server rejects an authentication	attempt	with a	535  reply  code.   As
       long  as	the smtp_sasl_password_maps information	does no	change,	and as
       long as the smtp_sasl_auth_cache_name information does not expire  (see
       smtp_sasl_auth_cache_time)  the Postfix SMTP client avoids SASL authen-
       tication	attempts with the same server, username	and password, and  in-
       stead	bounces	   or	 defers	   mail	  as   controlled   with   the
       smtp_sasl_auth_soft_bounce configuration	parameter.

       Use  a  per-destination	delivery  concurrency  of  1   (for   example,
       "smtp_destination_concurrency_limit  =  1",  "relay_destination_concur-
       rency_limit = 1", etc.),	otherwise multiple delivery agents may experi-
       ence a login failure at the same	time.

       The  table  must	 be  accessed via the proxywrite service, i.e. the map
       name must start with "proxy:". The table	should be stored under the di-
       rectory specified with the data_directory parameter.

       This  feature  uses  cryptographic  hashing to protect plain-text pass-
       words, and requires that	Postfix	is compiled with TLS support.

       Example:

       smtp_sasl_auth_cache_name = proxy:btree:/var/lib/postfix/sasl_auth_cache

       This feature is available in Postfix 2.5	and later.

smtp_sasl_auth_cache_time (default: 90d)
       The maximal age of an smtp_sasl_auth_cache_name entry before it is  re-
       moved.

       This feature is available in Postfix 2.5	and later.

smtp_sasl_auth_enable (default:	no)
       Enable SASL authentication in the Postfix SMTP client.  By default, the
       Postfix SMTP client uses	no authentication.

       Example:

       smtp_sasl_auth_enable = yes

smtp_sasl_auth_soft_bounce (default: yes)
       When a remote SMTP server rejects a SASL	authentication request with  a
       535  reply code,	defer mail delivery instead of returning mail as unde-
       liverable. The latter behavior was hard-coded prior to Postfix  version
       2.5.

       Note: the setting "yes" overrides the global soft_bounce	parameter, but
       the setting "no"	does not.

       Example:

       # Default as of Postfix 2.5
       smtp_sasl_auth_soft_bounce = yes
       # The old hard-coded default
       smtp_sasl_auth_soft_bounce = no

       This feature is available in Postfix 2.5	and later.

smtp_sasl_mechanism_filter (default: empty)
       If non-empty, a Postfix SMTP client filter for the remote SMTP server's
       list of offered SASL mechanisms.	 Different client and server implemen-
       tations may support different mechanism lists. By default, the  Postfix
       SMTP  client  will  use	the  intersection of the two. smtp_sasl_mecha-
       nism_filter further restricts what server mechanisms  the  client  will
       take into consideration.

       Specify	mechanism  names, "/file/name" patterns	or "type:table"	lookup
       tables. The right-hand side result from	"type:table"  lookups  is  ig-
       nored.  Specify	"!pattern"  to exclude a mechanism name	from the list.
       The form	"!/file/name" is supported only	in  Postfix  version  2.4  and
       later.

       This feature is available in Postfix 2.2	and later.

       Examples:

       smtp_sasl_mechanism_filter = plain, login
       smtp_sasl_mechanism_filter = /usr/local/etc/postfix/smtp_mechs
       smtp_sasl_mechanism_filter = !gssapi, !login, static:rest

smtp_sasl_password_maps	(default: empty)
       Optional	SMTP client lookup tables with one username:password entry per
       remote hostname or domain, or sender address when sender-dependent  au-
       thentication  is	enabled.  If no	username:password entry	is found, then
       the Postfix SMTP	client will not	attempt	to authenticate	to the	remote
       host.

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

smtp_sasl_path (default: empty)
       Implementation-specific information that	the Postfix SMTP client	passes
       through	to  the	 SASL  plug-in	implementation	that  is selected with
       smtp_sasl_type.	Typically this specifies the name of  a	 configuration
       file or rendezvous point.

       This feature is available in Postfix 2.3	and later.

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

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

       Specify zero or more of the following:

       noplaintext
	      Disallow methods that use	plaintext passwords.

       noactive
	      Disallow methods subject to active (non-dictionary) attack.

       nodictionary
	      Disallow methods subject to passive (dictionary) attack.

       noanonymous
	      Disallow methods that allow anonymous authentication.

       mutual_auth
	      Only allow  methods  that	 provide  mutual  authentication  (not
	      available	with SASL version 1).

       Example:

       smtp_sasl_security_options = noplaintext

smtp_sasl_tls_security_options (default: $smtp_sasl_security_options)
       The  SASL  authentication security options that the Postfix SMTP	client
       uses for	TLS encrypted SMTP sessions.

       This feature is available in Postfix 2.2	and later.

smtp_sasl_tls_verified_security_options	(default:  $smtp_sasl_tls_security_op-
       tions)
       The  SASL  authentication security options that the Postfix SMTP	client
       uses for	TLS encrypted SMTP sessions with a  verified  server  certifi-
       cate.

       When  mail  is  sent  to	the public MX host for the recipient's domain,
       server certificates are by default optional, and	delivery proceeds even
       if  certificate	verification fails. For	delivery via a submission ser-
       vice that requires SASL authentication, it may be appropriate  to  send
       plaintext  passwords only when the connection to	the server is strongly
       encrypted and the server	identity is verified.

       The smtp_sasl_tls_verified_security_options parameter makes it possible
       to  only	 enable	 plaintext  mechanisms when a secure connection	to the
       server is available. Submission servers subject to this policy must ei-
       ther  have verifiable certificates or offer suitable non-plaintext SASL
       mechanisms.

       This feature is available in Postfix 2.6	and later.

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

       This feature is available in Postfix 2.3	and later.

smtp_send_xforward_command (default: no)
       Send the	non-standard XFORWARD command when  the	 Postfix  SMTP	server
       EHLO response announces XFORWARD	support.

       This  allows  an	 "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  localhost[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,  Postfix  moves  on  the  next  mail  exchanger.  Specify
       "smtp_skip_4xx_greeting = no" if	Postfix	should defer delivery  immedi-
       ately.

       This  feature  is  available in Postfix 2.0 and earlier.	 Later Postfix
       versions	always skip SMTP servers that greet with a 4XX status code.

smtp_skip_5xx_greeting (default: yes)
       Skip SMTP servers that greet with a 5XX status code (go	away,  do  not
       try again later).

       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.  The default setting is incorrect, but it is what a	lot of
       people expect to	happen.

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)
       The  file with the certificate of the certification authority (CA) that
       issued the Postfix SMTP client certificate.  This is needed  only  when
       the  CA	certificate  is	 not already present in	the client certificate
       file.

       Example:

       smtp_tls_CAfile = /usr/local/etc/postfix/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.

       Example:

       smtp_tls_CApath = /usr/local/etc/postfix/certs

       This feature is available in Postfix 2.2	and later.

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.

       In  order to verify certificates, the CA	certificate (in	case of	a cer-
       tificate	chain, all CA certificates) must be available.	You should add
       these  certificates  to	the client certificate,	the client certificate
       first, then the issuing CA(s).

       Example:	the certificate	for "client.dom.ain" was issued	by "intermedi-
       ate  CA"	 which	itself	has  a	certificate  of	"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 = /usr/local/etc/postfix/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: export)
       The minimum TLS cipher grade that the Postfix SMTP client will use with
       opportunistic  TLS  encryption.	Cipher	types  listed  in smtp_tls_ex-
       clude_ciphers are excluded from the base	definition of the selected ci-
       pher  grade. The	default	value "export" ensures maximum inter-operabil-
       ity. Because encryption is optional, stronger controls are  not	appro-
       priate, and this	setting	SHOULD NOT be changed unless the change	is es-
       sential.

       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.

       Example:
       smtp_tls_ciphers	= export

       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 = /usr/local/etc/postfix/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 = /usr/local/etc/postfix/ecdsa-ccert.pem

       This feature is available in Postfix 2.6	and  later,  when  Postfix  is
       compiled	and linked with	OpenSSL	0.9.9 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	0.9.9 or later.

smtp_tls_enforce_peername (default: yes)
       With mandatory TLS encryption, require  that  the  remote  SMTP	server
       hostname	matches	the information	in the remote SMTP server certificate.
       As of RFC 2487 the requirements for hostname checking for  MTA  clients
       are not specified.

       This  option  can  be set to "no" to disable strict peer	name checking.
       This setting has	no effect on sessions  that  are  controlled  via  the
       smtp_tls_per_site table.

       Disabling  the  hostname	verification can make sense in closed environ-
       ment where special CAs are created.  If not used	carefully, this	option
       opens  the  danger  of  a "man-in-the-middle" attack (the CommonName of
       this attacker will be logged).

       This feature is available in Postfix 2.2	and later.  With  Postfix  2.3
       and later use smtp_tls_security_level instead.

smtp_tls_exclude_ciphers (default: empty)
       List of ciphers or cipher types to exclude from the Postfix SMTP	client
       cipher list at all TLS security levels. This  is	 not  an  OpenSSL  ci-
       pherlist,  it  is  a simple list	separated by whitespace	and/or commas.
       The elements are	a single cipher, or one	or more	"+"  separated	cipher
       properties,  in which case only ciphers matching	all the	properties are
       excluded.

       Examples	(some of these will cause problems):

	   smtp_tls_exclude_ciphers = aNULL
	   smtp_tls_exclude_ciphers = MD5, DES
	   smtp_tls_exclude_ciphers = DES+MD5
	   smtp_tls_exclude_ciphers = AES256-SHA, DES-CBC3-MD5
	   smtp_tls_exclude_ciphers = kEDH+aRSA

       The first setting, disables anonymous ciphers. The  next	 setting  dis-
       ables ciphers that use the MD5 digest algorithm or the (single) DES en-
       cryption	algorithm. The next setting disables ciphers that use MD5  and
       DES  together.	The next setting disables the two ciphers "AES256-SHA"
       and "DES-CBC3-MD5". The last setting disables ciphers  that  use	 "EDH"
       key exchange with RSA authentication.

       This feature is available in Postfix 2.3	and later.

smtp_tls_fingerprint_cert_match	(default: empty)
       List  of	acceptable remote SMTP server certificate fingerprints for the
       "fingerprint" TLS security  level  (smtp_tls_security_level  =  finger-
       print).	At  this security level, certificate authorities are not used,
       and certificate expiration times	are ignored. Instead, server  certifi-
       cates are verified directly via their "fingerprint". The	fingerprint is
       a message digest	of the server certificate. The digest algorithm	is se-
       lected via the smtp_tls_fingerprint_digest parameter.

       When  an	 smtp_tls_policy_maps  table entry specifies the "fingerprint"
       security	level, any "match" attributes in that entry specify  the  list
       of  valid fingerprints for the corresponding destination. Multiple fin-
       gerprints can be	combined with a	"|" delimiter in a single match	attri-
       bute, or	multiple match attributes can be employed.

       Example:	 Certificate  fingerprint  verification	with internal mailhub.
       Two matching fingerprints are listed. The  relayhost  may  be  multiple
       physical	hosts behind a load-balancer, each with	its own	private/public
       key and self-signed certificate.	Alternatively, a single	relayhost  may
       be  in  the process of switching	from one set of	private/public keys to
       another,	and both keys are trusted just prior to	the transition.

	   relayhost = [mailhub.example.com]
	   smtp_tls_security_level = fingerprint
	   smtp_tls_fingerprint_digest = md5
	   smtp_tls_fingerprint_cert_match =
	       3D:95:34:51:24:66:33:B9:D2:40:99:C0:C1:17:0B:D1
	       EC:3B:2D:B0:5B:B1:FB:6D:20:A3:9D:72:F6:8D:12:35

       Example:	Certificate fingerprint	verification  with  selected  destina-
       tions.  As in the example above,	we show	two matching fingerprints:

	   /usr/local/etc/postfix/main.cf:
	       smtp_tls_policy_maps = hash:/usr/local/etc/postfix/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 fingerprint. The fingerprint is the mes-
       sage  digest  of	 the  server certificate 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 that
       has the same fingerprint.

       The default algorithm is	md5; this is  consistent  with	the  backwards
       compatible  setting of the digest used to verify	client certificates in
       the SMTP	server.

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

       While  additional  digest algorithms are	often available	with OpenSSL's
       libcrypto, only those used by libssl in SSL cipher suites are available
       to Postfix. For now this	means just md5 or sha1.

       To find the fingerprint of a specific certificate file, with a specific
       digest algorithm, run:

	   $ openssl x509 -noout -fingerprint -digest -in certfile.pem

       The text	to the right of	"=" sign is the	desired	fingerprint.  For  ex-
       ample:

	   $ openssl x509 -noout -fingerprint -sha1 -in	cert.pem
	   SHA1	Fingerprint=D4:6A:AB:19:24:79:F8:32:BB:A6:CB:66:82:C0:8E:9B:EE:29:A8:1A

       This feature is available in Postfix 2.5	and later.

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 TLS	handshake and certificate information.

	      2	Log levels during TLS negotiation.

	      3	Log hexadecimal	and ASCII dump of TLS negotiation process.

	      4	 Log hexadecimal and ASCII dump	of complete transmission after
	      STARTTLS.

       Use "smtp_tls_loglevel =	3" only	in case	of problems. 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 crypt-analytic 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  the mainstream "EXPORT" grade or better OpenSSL ciphers.
	      This is always used for opportunistic encryption.	It is not rec-
	      ommended	for  mandatory	encryption unless you must enforce TLS
	      with "crippled" peers. The underlying  cipherlist	 is  specified
	      via the tls_export_cipherlist configuration parameter, which you
	      are strongly encouraged to not  change.  The  default  value  of
	      tls_export_cipherlist  includes anonymous	ciphers, but these are
	      automatically filtered out if the	client is configured to	verify
	      server  certificates. If you must	exclude	anonymous ciphers also
	      at the "encrypt"	security  level,  set  "smtp_tls_mandatory_ex-
	      clude_ciphers = aNULL".

       low    Enable  the  mainstream  "LOW"  grade or better OpenSSL ciphers.
	      This setting is only appropriate for internal mail servers.  The
	      underlying  cipherlist  is  specified via	the tls_low_cipherlist
	      configuration parameter, which you are  strongly	encouraged  to
	      not  change.  The	 default  value	of tls_low_cipherlist includes
	      anonymous	ciphers, but these are automatically filtered  out  if
	      the  client  is configured to verify server certificates.	If you
	      must exclude anonymous ciphers also at  the  "encrypt"  security
	      level, set "smtp_tls_mandatory_exclude_ciphers = aNULL".

       medium Enable  the mainstream "MEDIUM" grade or better OpenSSL ciphers.
	      The underlying cipherlist	is specified  via  the	tls_medium_ci-
	      pherlist configuration parameter,	which you are strongly encour-
	      aged to not change.  The default value of	 tls_medium_cipherlist
	      includes anonymous ciphers, but these are	automatically filtered
	      out if the client	is configured to verify	 server	 certificates.
	      If  you must exclude anonymous ciphers also at the "encrypt" se-
	      curity level, set	"smtp_tls_mandatory_exclude_ciphers = aNULL".

       high   Enable only the mainstream "HIGH"	grade OpenSSL  ciphers.	  This
	      setting  is appropriate when all mandatory TLS destinations sup-
	      port some	of "HIGH" grade	ciphers, this is not uncommon. The un-
	      derlying	cipherlist  is	specified  via the tls_high_cipherlist
	      configuration parameter, which you are  strongly	encouraged  to
	      not  change.  The	 default value of tls_high_cipherlist includes
	      anonymous	ciphers, but these are automatically filtered  out  if
	      the  client  is configured to verify server certificates.	If you
	      must exclude anonymous ciphers also at  the  "encrypt"  security
	      level, set "smtp_tls_mandatory_exclude_ciphers = aNULL".

       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  default
	      value of tls_null_cipherlist excludes anonymous ciphers (OpenSSL
	      0.9.8 has	NULL ciphers that offer	data integrity without encryp-
	      tion or authentication).

       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 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"	attri-
       bute. See smtp_tls_policy_maps for notes	and examples.

       This feature is available in Postfix 2.3	and later.

smtp_tls_mandatory_protocols (default: SSLv3, TLSv1)
       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".

       With  Postfix >=	2.5 the	parameter syntax is expanded to	support	proto-
       col exclusions.	One  can  now  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 still sup-
       ported; use the form you	find more intuitive.

       Since SSL version 2 has known protocol weaknesses  and  is  now	depre-
       cated,  the  default  setting excludes "SSLv2".	This means that	by de-
       fault, SSL version 2 will not be	used at	the "encrypt"  security	 level
       and higher.

       See   the  documentation	 of  the  smtp_tls_policy_maps	parameter  and
       TLS_README for more information about security levels.

       Example:

       smtp_tls_mandatory_protocols = TLSv1
       # Alternative form with Postfix >= 2.5:
       smtp_tls_mandatory_protocols = !SSLv2, !SSLv3

       This feature is available in Postfix 2.3	and later.

smtp_tls_note_starttls_offer (default: no)
       Log the hostname	of a remote SMTP server	that offers STARTTLS, when TLS
       is not already enabled for that server.

       The logfile record looks	like:

       postfix/smtp[pid]:  Host	offered	STARTTLS: [name.of.host]

       This feature is available in Postfix 2.2	and later.

smtp_tls_per_site (default: empty)
       Optional	lookup tables with the Postfix SMTP client TLS usage policy by
       next-hop	destination and	by remote SMTP	server	hostname.   When  both
       lookups	succeed,  the  more specific per-site policy (NONE, MUST, etc)
       overrides the less specific one (MAY), and  the	more  secure  per-site
       policy  (MUST, etc) overrides the less secure one (NONE).  With Postfix
       2.3  and	 later	smtp_tls_per_site   is	 strongly   discouraged:   use
       smtp_tls_policy_maps instead.

       Use  of	the bare hostname as the per-site table	lookup key is discour-
       aged. Always use	the full destination nexthop (enclosed in  []  with  a
       possible	 ":port"  suffix).  A recipient	domain or MX-enabled transport
       next-hop	with no	port suffix may	look like  a  bare  hostname,  but  is
       still a suitable	destination.

       Specify	a  next-hop  destination  or  server hostname on the left-hand
       side; no	wildcards are allowed. The next-hop destination	is either  the
       recipient  domain, or the destination specified with a transport(5) ta-
       ble, the	relayhost parameter, or	the relay_transport parameter.	On the
       right hand side specify one of the following keywords:

       NONE   Don't  use TLS at	all. This overrides a less specific MAY	lookup
	      result from the alternate	host or	next-hop lookup	key, and over-
	      rides    the    global   smtp_use_tls,   smtp_enforce_tls,   and
	      smtp_tls_enforce_peername	settings.

       MAY    Try to use TLS if	the server announces  support,	otherwise  use
	      the unencrypted connection. This has less	precedence than	a more
	      specific result (including NONE)	from  the  alternate  host  or
	      next-hop	lookup key, and	has less precedence than the more spe-
	      cific global "smtp_enforce_tls = yes" or "smtp_tls_enforce_peer-
	      name = yes".

       MUST_NOPEERMATCH
	      Require  TLS encryption, but do not require that the remote SMTP
	      server hostname matches  the  information	 in  the  remote  SMTP
	      server certificate, or that the server certificate was issued by
	      a	trusted	CA. This overrides a less secure NONE or a  less  spe-
	      cific  MAY  lookup  result  from	the alternate host or next-hop
	      lookup key, and  overrides  the  global  smtp_use_tls,  smtp_en-
	      force_tls	and smtp_tls_enforce_peername settings.

       MUST   Require  TLS  encryption,	 require  that	the remote SMTP	server
	      hostname matches the information in the remote SMTP server  cer-
	      tificate,	 and  require  that the	remote SMTP server certificate
	      was issued by a trusted CA. This overrides a  less  secure  NONE
	      and  MUST_NOPEERMATCH  or	a less specific	MAY lookup result from
	      the alternate host or next-hop lookup  key,  and	overrides  the
	      global smtp_use_tls, smtp_enforce_tls and	smtp_tls_enforce_peer-
	      name settings.

       The above keywords correspond to	the "none", "may", "encrypt" and "ver-
       ify"  security levels for the new smtp_tls_security_level parameter in-
       troduced	in Postfix 2.3.	Starting with Postfix 2.3,  and	 independently
       of  how	the  policy  is	 specified, the	smtp_tls_mandatory_ciphers and
       smtp_tls_mandatory_protocols parameters apply when  TLS	encryption  is
       mandatory.  Connections	for which encryption is	optional typically en-
       able all	"export" grade and better ciphers and  all  SSL/TLS  protocols
       (see smtp_tls_ciphers and smtp_tls_protocols).

       As long as no secure DNS	lookup mechanism is available, false hostnames
       in MX or	CNAME responses	can change the server  hostname	 that  Postfix
       uses  for  TLS  policy lookup and server	certificate verification. Even
       with a perfect match between the	server hostname	and  the  server  cer-
       tificate,  there	is no guarantee	that Postfix is	connected to the right
       server.	See TLS_README (Closing	a DNS loophole with obsolete  per-site
       TLS policies) for a possible work-around.

       This  feature  is  available in Postfix 2.2 and later. With Postfix 2.3
       and later use smtp_tls_policy_maps instead.

smtp_tls_policy_maps (default: empty)
       Optional	lookup tables with the Postfix SMTP client TLS security	policy
       by  next-hop  destination;  when	 a  non-empty value is specified, this
       overrides the obsolete smtp_tls_per_site	parameter.  See	TLS_README for
       a more detailed discussion of TLS security levels.

       The TLS policy table is indexed by the full next-hop destination, which
       is either the recipient domain, or the verbatim next-hop	 specified  in
       the   transport	 table,	  $local_transport,  $virtual_transport,  $re-
       lay_transport or	$default_transport. This includes any enclosing	square
       brackets	 and  any non-default destination server port suffix. The LMTP
       socket type prefix (inet: or unix:) is not included in the lookup key.

       Only the	next-hop domain, or $myhostname	 with  LMTP  over  UNIX-domain
       sockets,	 is used as the	nexthop	name for certificate verification. The
       port and	any enclosing square brackets are used	in  the	 table	lookup
       key, but	are not	used for server	name verification.

       When  the lookup	key is a domain	name without enclosing square brackets
       or any :port suffix (typically the recipient domain), and the full  do-
       main  is	 not  found in the table, just as with the transport(5)	table,
       the parent domain starting with a leading "." is	 matched  recursively.
       This allows one to specify a security policy for	a recipient domain and
       all its sub-domains.

       The lookup result is a security level, followed by an optional list  of
       whitespace  and/or  comma separated name=value attributes that override
       related main.cf settings. The TLS security levels in order of  increas-
       ing security are:

       none   No TLS. No additional attributes are supported at	this level.

       may    Opportunistic TLS. Since sending in the clear is acceptable, de-
	      manding stronger than default TLS	security merely	reduces	inter-
	      operability.  The	 optional "ciphers", "exclude" and "protocols"
	      attributes (available for	opportunistic TLS with Postfix >= 2.6)
	      override	the "smtp_tls_ciphers",	"smtp_tls_exclude_ciphers" and
	      "smtp_tls_protocols" configuration parameters. When  opportunis-
	      tic TLS handshakes fail, Postfix retries the connection with TLS
	      disabled.	 This allows mail delivery to sites with  non-interop-
	      erable TLS implementations.

       encrypt
	      Mandatory	TLS encryption.	At this	level and higher, the optional
	      "protocols"  attribute  overrides	 the  main.cf  smtp_tls_manda-
	      tory_protocols parameter,	the optional "ciphers" attribute over-
	      rides the	main.cf	smtp_tls_mandatory_ciphers parameter, and  the
	      optional	"exclude"  attribute  (Postfix	>=  2.6) overrides the
	      main.cf  smtp_tls_mandatory_exclude_ciphers  parameter.  In  the
	      policy  table,  multiple	protocols  or excluded ciphers must be
	      separated	by colons, as attribute	values may not contain	white-
	      space or commas.

       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	valid "fingerprints" of	the  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:/usr/local/etc/postfix/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: empty)
       List  of	TLS protocols that the Postfix SMTP client will	exclude	or in-
       clude with opportunistic	TLS encryption.	This parameter SHOULD be  left
       at  its default empty value, allowing all protocols to be used with op-
       portunistic 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".

       To  include  a  protocol	 list its name,	to exclude it, prefix the name
       with a "!" character. To	exclude	SSLv2 even 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,  is	 supported,  but  not recommended. OpenSSL provides no
       mechanisms for excluding	protocols not known at compile-time. If	 Post-
       fix  is linked against an OpenSSL library that supports additional pro-
       tocol versions, they cannot be excluded using either syntax.

       Example:
       smtp_tls_protocols = !SSLv2

       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)
       The  server  certificate	 peername verification method for the "secure"
       TLS security level. In a	 "secure"  TLS	policy	table  ($smtp_tls_pol-
       icy_maps)  entry	 the optional "match" attribute	overrides this main.cf
       setting.

       This parameter specifies	one or more patterns or	 strategies  separated
       by  commas,  whitespace	or colons.  In the policy table	the only valid
       separator is the	colon character.

       For  a  description  of	the  pattern  and  strategy  syntax  see   the
       smtp_tls_verify_cert_match parameter. The "hostname" strategy should be
       avoided in this context,	as in the absence of a secure global DNS,  us-
       ing the results of MX lookups in	certificate verification is not	immune
       to active (man-in-the-middle) attacks on	DNS.

       Sample main.cf setting:

	   smtp_tls_secure_cert_match =	nexthop

       Sample policy table override:

	   example.net	   secure match=example.com:.example.com
	   .example.net	   secure match=example.com:.example.com

       This feature is available in Postfix 2.3	and later.

smtp_tls_security_level	(default: empty)
       The default SMTP	TLS security level for the Postfix SMTP	client;	when a
       non-empty  value	 is  specified,	this overrides the obsolete parameters
       smtp_use_tls, smtp_enforce_tls, and smtp_tls_enforce_peername.

       Specify one of the following security levels:

       none   TLS will not be used unless enabled  for	specific  destinations
	      via smtp_tls_policy_maps.

       may    Opportunistic  TLS.  Use	TLS if this is supported by the	remote
	      SMTP server, otherwise use plaintext. Since sending in the clear
	      is  acceptable,  demanding  stronger  than  default TLS security
	      merely reduces inter-operability.	  The  "smtp_tls_ciphers"  and
	      "smtp_tls_protocols"  (Postfix  >= 2.6) configuration parameters
	      provide control over the protocols and cipher  grade  used  with
	      opportunistic  TLS.  With	earlier	releases the opportunistic TLS
	      cipher grade is always "export" and no protocols	are  disabled.
	      When  TLS	 handshakes  fail,  the	connection is retried with TLS
	      disabled.	 This allows mail delivery to sites with  non-interop-
	      erable TLS implementations.

       encrypt
	      Mandatory	 TLS  encryption. Since	a minimum level	of security is
	      intended,	it is reasonable to be specific	about sufficiently se-
	      cure  protocol  versions and ciphers. At this security level and
	      higher, the main.cf parameters smtp_tls_mandatory_protocols  and
	      smtp_tls_mandatory_ciphers specify the TLS protocols and minimum
	      cipher grade which the administrator considers secure enough for
	      mandatory	 encrypted sessions. This security level is not	an ap-
	      propriate	default	for systems delivering mail to the Internet.

       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   smtp_tls_finger-
	      print_cert_match parameter lists the valid "fingerprints"	of the
	      server  certificate.  The	digest algorithm used to calculate the
	      fingerprint is selected by the  smtp_tls_fingerprint_digest  pa-
	      rameter.

       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 protocols unless	it is essential
       # to do so (if a	security vulnerability is found	in the SSL library that
       # can be	mitigated by disabling a particular protocol or	raising	the
       # cipher	grade from "export" to "low" or	"medium").
       smtp_tls_ciphers	= export
       smtp_tls_protocols =

       # 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.

       This feature is available in Postfix 2.2	and later.

smtp_tls_verify_cert_match (default: hostname)
       The  server  certificate	 peername verification method for the "verify"
       TLS security level. In a	 "verify"  TLS	policy	table  ($smtp_tls_pol-
       icy_maps)  entry	 the optional "match" attribute	overrides this main.cf
       setting.

       This parameter specifies	one or more patterns or	 strategies  separated
       by  commas,  whitespace	or colons.  In the policy table	the only valid
       separator is the	colon character.

       Patterns	specify	domain names, or domain	name suffixes:

       example.com
	      Match the	example.com domain, i.e. one of	the names  the	server
	      certificate  must	 be example.com, upper and lower case distinc-
	      tions are	ignored.

       .example.com
	      Match subdomains of the example.com domain, i.e. match a name in
	      the server certificate that consists of a	non-zero number	of la-
	      bels followed by a .example.com suffix.  Case  distinctions  are
	      ignored.

       Strategies specify a transformation from	the next-hop domain to the ex-
       pected name in the server certificate:

       nexthop
	      Match against the	next-hop domain, which is either the recipient
	      domain,  or  the	transport  next-hop  configured	for the	domain
	      stripped of any optional socket type  prefix,  enclosing	square
	      brackets	and trailing port. When	MX lookups are not suppressed,
	      this is the original nexthop domain prior	to the MX lookup,  not
	      the  result  of the MX lookup. For LMTP delivery via UNIX-domain
	      sockets, the verified next-hop name is $myhostname.  This	strat-
	      egy  is  suitable	 for use with the "secure" policy. Case	is ig-
	      nored.

       dot-nexthop
	      As above,	but match server certificate names that	are subdomains
	      of the next-hop domain. Case is ignored.

       hostname
	      Match  against the hostname of the server, often obtained	via an
	      unauthenticated DNS MX lookup. For LMTP delivery via UNIX-domain
	      sockets, the verified name is $myhostname. This matches the ver-
	      ification	 strategy  of  the  "MUST"  keyword  in	 the  obsolete
	      smtp_tls_per_site	 table,	and is suitable	for use	with the "ver-
	      ify" security level. When	 the  next-hop	name  is  enclosed  in
	      square  brackets to suppress MX lookups, the "hostname" strategy
	      is the same as the "nexthop" strategy. Case is ignored.

       Sample main.cf setting:

       smtp_tls_verify_cert_match = hostname, nexthop, dot-nexthop

       Sample policy table override:

       example.com     verify  match=hostname:nexthop
       .example.com    verify  match=example.com:.example.com:hostname

       This feature is available in Postfix 2.3	and later.

smtp_use_tls (default: no)
       Opportunistic mode: use TLS when	a remote SMTP server announces	START-
       TLS  support,  otherwise	 send the mail in the clear. Beware: some SMTP
       servers offer STARTTLS even if it is not	configured.   With  Postfix  <
       2.3,  if	the TLS	handshake fails, and no	other server is	available, de-
       livery is deferred and mail stays in the	queue. If this	is  a  concern
       for you,	use the	smtp_tls_per_site feature instead.

       This  feature  is  available in Postfix 2.2 and later. With Postfix 2.3
       and later use smtp_tls_security_level instead.

smtp_xforward_timeout (default:	300s)
       The SMTP	client time limit for sending the XFORWARD  command,  and  for
       receiving the 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 SMTP clients are allowed to	specify	the XVERP command.  This  com-
       mand requests that mail be delivered one	recipient at a time with a per
       recipient return	address.

       By default, no clients are allowed to specify XVERP.

       This parameter was renamed with Postfix version 2.1. The	default	 value
       is backwards compatible with Postfix version 2.0.

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

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

smtpd_authorized_xclient_hosts (default: empty)
       What SMTP clients are allowed to	use the	XCLIENT	feature.  This command
       overrides SMTP client information that is used for access control. Typ-
       ical use	is for SMTP-based content filters, fetchmail-like programs, or
       SMTP server access rule testing.	See the	 XCLIENT_README	 document  for
       details.

       This feature is available in Postfix 2.1	and later.

       By default, no clients are allowed to specify XCLIENT.

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

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

smtpd_authorized_xforward_hosts	(default: empty)
       What  SMTP  clients are allowed to use the XFORWARD feature.  This com-
       mand 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 re-
       placed by its contents; a "type:table" lookup table is matched  when  a
       table  entry  matches  a	 lookup	string (the lookup result is ignored).
       Continue	long lines by starting the next	line with whitespace.  Specify
       "!pattern"  to  exclude	an address or network block from the list. The
       form "!/file/name" is supported only in Postfix version 2.4 and later.

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

smtpd_banner (default: $myhostname ESMTP $mail_name)
       The  text that follows the 220 status code in the SMTP greeting banner.
       Some people like	to see the mail	version	advertised. By default,	 Post-
       fix shows no version.

       You MUST	specify	$myhostname at the start of the	text. This is required
       by the SMTP protocol.

       Example:

       smtpd_banner = $myhostname ESMTP	$mail_name ($mail_version)

smtpd_client_connection_count_limit (default: 50)
       How many	simultaneous connections any client is allowed to make to this
       service.	  By  default,	the  limit  is set to half the default process
       limit value.

       To disable this feature,	specify	a limit	of 0.

       WARNING:	The purpose of this feature is to limit	abuse. It must not  be
       used to regulate	legitimate mail	traffic.

       This feature is available in Postfix 2.2	and later.

smtpd_client_connection_rate_limit (default: 0)
       The maximal number of connection	attempts any client is allowed to make
       to this service per time	unit.  The time	unit  is  specified  with  the
       anvil_rate_time_unit configuration parameter.

       By  default,  a	client	can  make as many connections per time unit as
       Postfix can accept.

       To disable this feature,	specify	a limit	of 0.

       WARNING:	The purpose of this feature is to limit	abuse. It must not  be
       used to regulate	legitimate mail	traffic.

       This feature is available in Postfix 2.2	and later.

       Example:

       smtpd_client_connection_rate_limit = 1000

smtpd_client_event_limit_exceptions (default: $mynetworks)
       Clients	that  are  excluded from connection count, connection rate, or
       SMTP request rate restrictions. See the mynetworks  parameter  descrip-
       tion for	the parameter value syntax.

       By default, clients in trusted networks are excluded. Specify a list of
       network blocks, hostnames or .domain names (the initial dot causes  the
       domain to match any name	below it).

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

       This feature is available in Postfix 2.2	and later.

smtpd_client_message_rate_limit	(default: 0)
       The maximal number of message delivery requests that any	client is  al-
       lowed  to  make to this service per time	unit, regardless of whether or
       not Postfix actually accepts those messages.  The time unit  is	speci-
       fied with the anvil_rate_time_unit configuration	parameter.

       By  default,  a	client	can send as many message delivery requests per
       time unit as Postfix can	accept.

       To disable this feature,	specify	a limit	of 0.

       WARNING:	The purpose of this feature is to limit	abuse. It must not  be
       used to regulate	legitimate mail	traffic.

       This feature is available in Postfix 2.2	and later.

       Example:

       smtpd_client_message_rate_limit = 1000

smtpd_client_new_tls_session_rate_limit	(default: 0)
       The  maximal  number of new (i.e., uncached) TLS	sessions that a	remote
       SMTP client is allowed to negotiate with	this service  per  time	 unit.
       The  time unit is specified with	the anvil_rate_time_unit configuration
       parameter.

       By default, a remote SMTP client	can negotiate as many new TLS sessions
       per time	unit as	Postfix	can accept.

       To  disable  this  feature,  specify a limit of 0. Otherwise, specify a
       limit that is at	least the per-client concurrent	session	limit, or else
       legitimate client sessions may be rejected.

       WARNING:	 The purpose of	this feature is	to limit abuse.	It must	not be
       used to regulate	legitimate mail	traffic.

       This feature is available in Postfix 2.3	and later.

       Example:

       smtpd_client_new_tls_session_rate_limit = 100

smtpd_client_port_logging (default: no)
       Enable logging of the remote SMTP client	port in	addition to the	 host-
       name and	IP address. The	logging	format is "host[address]:port".

       This feature is available in Postfix 2.5	and later.

smtpd_client_recipient_rate_limit (default: 0)
       The maximal number of recipient addresses that any client is allowed to
       send to this service per	time unit, regardless of whether or not	 Post-
       fix actually accepts those recipients.  The time	unit is	specified with
       the anvil_rate_time_unit	configuration parameter.

       By default, a client can	make 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	SMTP server access restrictions	in the	context	 of  a	client
       SMTP connection request.

       The default is to allow all connection requests.

       Specify	a list of restrictions,	separated by commas and/or whitespace.
       Continue	long lines by starting the next	 line  with  whitespace.   Re-
       strictions are applied in the order as specified; the first restriction
       that matches wins.

       The following restrictions are specific to client  hostname  or	client
       network address information.

       check_ccert_access type:table
	      Use  the	client	certificate  fingerprint as lookup key for the
	      specified	access(5) database; with Postfix version 2.2, also re-
	      quire that the SMTP client certificate is	verified successfully.
	      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_reverse_client_hostname_access type:table
	      Search the specified access database for the unverified  reverse
	      client  hostname,	parent domains,	client IP address, or networks
	      obtained by stripping least  significant	octets.	 See  the  ac-
	      cess(5)  manual page for details.	 Note: a result	of "OK"	is not
	      allowed for safety reasons.  Instead, use	DUNNO in order to  ex-
	      clude specific hosts from	blacklists.  This feature is available
	      in Postfix 2.6 and later.

       permit_inet_interfaces
	      Permit the request when the client IP address matches  $inet_in-
	      terfaces.

       permit_mynetworks
	      Permit  the  request when	the client IP address matches any net-
	      work or network address listed in	 $mynetworks.

       permit_sasl_authenticated
	      Permit the request when the client is successfully authenticated
	      via the RFC 4954 (AUTH) protocol.

       permit_tls_all_clientcerts
	      Permit  the  request  when the remote SMTP client	certificate is
	      verified successfully.  This option must be used only if a  spe-
	      cial  CA	issues	the certificates and only this CA is listed as
	      trusted CA, otherwise all	clients	with a recognized  certificate
	      would  be	allowed	to relay. This feature is available with Post-
	      fix version 2.2.

       permit_tls_clientcerts
	      Permit the request when the remote SMTP client certificate  fin-
	      gerprint	is  listed in $relay_clientcerts.  The fingerprint di-
	      gest algorithm is	configurable via the smtpd_tls_fingerprint_di-
	      gest 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).  If no "=d.d.d.d" is	specified, re-
	      ject  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_re-
	      ply_maps	parameter specifies tables with	server replies indexed
	      by rbl_domain.  This feature is available	 in  Postfix  2.0  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).   If  no "=d.d.d.d" is specified, reject the request when
	      the client hostname is listed with any A	record	under  rbl_do-
	      main. See	the reject_rbl_client description above	for additional
	      RBL related configuration	parameters.  This feature is available
	      in Postfix 2.0 and later.

       reject_unknown_client_hostname	(with	Postfix	  <   2.3:  reject_un-
       known_client)
	      Reject the request when 1) the client IP	address->name  mapping
	      fails,  2)  the name->address mapping fails, or 3) the name->ad-
	      dress mapping does not match the client IP address.
	      This is  a  stronger  restriction	 than  the  reject_unknown_re-
	      verse_client_hostname  feature, which triggers only under	condi-
	      tion 1) above.
	      The unknown_client_reject_code parameter specifies the  response
	      code  for	 rejected requests (default: 450). The reply is	always
	      450 in case the address->name or name->address lookup failed due
	      to a temporary problem.

       reject_unknown_reverse_client_hostname
	      Reject  the  request  when  the  client  IP  address  has	no ad-
	      dress->name mapping.
	      This   is	  a   weaker   restriction   than    the    reject_un-
	      known_client_hostname  feature, which requires not only that the
	      address->name and	name->address mappings exist,  but  also  that
	      the two mappings reproduce the client IP address.
	      The  unknown_client_reject_code parameter	specifies the response
	      code for rejected	requests (default: 450).  The reply is	always
	      450  in  case the	address->name lookup failed due	to a temporary
	      problem.
	      This feature is available	in Postfix 2.3 and later.

       In addition, you	can use	any of	the  following	generic	 restrictions.
       These restrictions are applicable in any	SMTP command context.

       check_policy_service servername
	      Query  the  specified policy server. See the SMTPD_POLICY_README
	      document for details. This feature is available in  Postfix  2.1
	      and later.

       defer  Defer  the  request. The client is told to try again later. This
	      restriction is useful at the end of a restriction	list, to  make
	      the default policy explicit.
	      The  defer_code  parameter  specifies the	SMTP server reply code
	      (default:	450).

       defer_if_permit
	      Defer the	request	if some	later restriction would	result	in  an
	      explicit	or  implicit  PERMIT  action.	This  is useful	when a
	      blacklisting feature fails due to	 a  temporary  problem.	  This
	      feature is available in Postfix version 2.1 and later.

       defer_if_reject
	      Defer  the  request  if some later restriction would result in a
	      REJECT action.  This is useful when a whitelisting feature fails
	      due  to a	temporary problem.  This feature is available in Post-
	      fix version 2.1 and later.

       permit Permit the request. This restriction is useful at	the end	 of  a
	      restriction list,	to make	the default policy explicit.

       reject_multi_recipient_bounce
	      Reject the request when the envelope sender is the null address,
	      and the message has multiple envelope recipients.	This usage has
	      rare  but	 legitimate  applications:  under  certain conditions,
	      multi-recipient mail that	was posted with	 the  DSN  option  NO-
	      TIFY=NEVER may be	forwarded with the null	sender address.
	      Note:  this  restriction	can  only  work	 reliably when used in
	      smtpd_data_restrictions or  smtpd_end_of_data_restrictions,  be-
	      cause  the total number of recipients is not known at an earlier
	      stage of the SMTP	conversation.  Use at the RCPT stage will only
	      reject the second	etc.  recipient.
	      The  multi_recipient_bounce_reject_code  parameter specifies the
	      response code for	rejected requests (default:  550).  This  fea-
	      ture is available	in Postfix 2.1 and later.

       reject_plaintext_session
	      Reject  the  request  when the connection	is not encrypted. This
	      restriction should not be	used  before  the  client  has	had  a
	      chance  to  negotiate  encryption	with the AUTH or STARTTLS com-
	      mands.
	      The plaintext_reject_code	parameter specifies the	response  code
	      for  rejected  requests (default:	 450).	This feature is	avail-
	      able in Postfix 2.3 and later.

       reject_unauth_pipelining
	      Reject the request when the client sends SMTP commands ahead  of
	      time where it is not allowed, or when the	client sends SMTP com-
	      mands ahead of time without knowing that Postfix	actually  sup-
	      ports  ESMTP  command pipelining.	This stops mail	from bulk mail
	      software that improperly uses ESMTP command pipelining in	 order
	      to speed up deliveries.
	      Note:    reject_unauth_pipelining	   is	not   useful   outside
	      smtpd_data_restrictions when 1) the client uses ESMTP (EHLO  in-
	      stead  of	 HELO) and 2) with "smtpd_delay_reject = yes" (the de-
	      fault).  The use of reject_unauth_pipelining in  the  other  re-
	      striction	contexts is therefore not recommended.

       reject Reject  the  request. This restriction is	useful at the end of a
	      restriction list,	to make	the default policy explicit.  The  re-
	      ject_code	 configuration	parameter  specifies the response code
	      for rejected requests (default: 554).

       sleep seconds
	      Pause for	the specified number of	seconds	and proceed  with  the
	      next  restriction	in the list, if	any. This may stop zombie mail
	      when used	as:
	      /usr/local/etc/postfix/main.cf:
		  smtpd_client_restrictions =
		      sleep 1, reject_unauth_pipelining
		  smtpd_delay_reject = no
	      This feature is available	in Postfix 2.3.

       warn_if_reject
	      Change the meaning of the	next restriction, so that  it  logs  a
	      warning instead of rejecting a request (look for logfile records
	      that contain "reject_warning"). This is useful for  testing  new
	      restrictions in a	"live" environment without risking unnecessary
	      loss of mail.

       Other restrictions that are valid in this context:

       o      SMTP command specific restrictions that are described under  the
	      smtpd_helo_restrictions,	smtpd_sender_restrictions or smtpd_re-
	      cipient_restrictions parameters. When helo, sender or  recipient
	      restrictions  are	 listed	 under smtpd_client_restrictions, they
	      have effect  only	 with  "smtpd_delay_reject  =  yes",  so  that
	      $smtpd_client_restrictions  is evaluated at the time of the RCPT
	      TO command.

       Example:

       smtpd_client_restrictions = permit_mynetworks, reject_unknown_client_hostname

smtpd_data_restrictions	(default: empty)
       Optional	access restrictions that the Postfix SMTP  server  applies  in
       the context of the SMTP DATA command.

       This feature is available in Postfix 2.0	and later.

       Specify	a list of restrictions,	separated by commas and/or whitespace.
       Continue	long lines by starting the next	 line  with  whitespace.   Re-
       strictions are applied in the order as specified; the first restriction
       that matches wins.

       The following restrictions are valid in this context:

       o      Generic restrictions that	can be used in any SMTP	 command  con-
	      text, described under smtpd_client_restrictions.

       o      SMTP    command	 specific    restrictions    described	 under
	      smtpd_client_restrictions,	      smtpd_helo_restrictions,
	      smtpd_sender_restrictions	or smtpd_recipient_restrictions.

       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 SMTP server receives a valid MAIL	FROM command.

       With  sites  that  reject lots of mail, the default setting reduces the
       use of disk, CPU	and memory resources. The downside  is	that  rejected
       recipients  are	logged	with NOQUEUE instead of	a mail transaction ID.
       This complicates	the logfile analysis of	multi-recipient	mail.

       This feature is available in Postfix 2.3	and later.

smtpd_delay_reject (default: yes)
       Wait until the RCPT TO command before evaluating	$smtpd_client_restric-
       tions, $smtpd_helo_restrictions and $smtpd_sender_restrictions, or wait
       until the ETRN command before evaluating	$smtpd_client_restrictions and
       $smtpd_helo_restrictions.

       This  feature  is  turned on by default because some clients apparently
       mis-behave when the Postfix SMTP	server rejects	commands  before  RCPT
       TO.

       The default setting has one major benefit: it allows Postfix to log re-
       cipient address information when	rejecting  a  client  name/address  or
       sender  address,	so that	it is possible to find out whose mail is being
       rejected.

smtpd_discard_ehlo_keyword_address_maps	(default: empty)
       Lookup tables, indexed by the remote SMTP client	address, with case in-
       sensitive  lists	 of  EHLO  keywords (pipelining, starttls, auth, etc.)
       that the	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 SMTP server will	not send in the	EHLO response to a re-
       mote 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.

       This feature is available in Postfix 2.2	and later.

       See smtpd_data_restrictions for syntax details.

smtpd_enforce_tls (default: no)
       Mandatory  TLS:	announce STARTTLS support to 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 off by default and should be used only on dedicated servers.

       Note 1: "smtpd_enforce_tls = yes" implies "smtpd_tls_auth_only =	yes".

       Note 2: when invoked via	 "sendmail  -bs",  Postfix  will  never	 offer
       STARTTLS	 due  to  insufficient privileges to access the	server private
       key. This is intended behavior.

       This feature is available in Postfix 2.2	and later.  With  Postfix  2.3
       and later use smtpd_tls_security_level instead.

smtpd_error_sleep_time (default: 1s)
       With  Postfix version 2.1 and later: the	SMTP server response delay af-
       ter a client has	made more  than	 $smtpd_soft_error_limit  errors,  and
       fewer than $smtpd_hard_error_limit errors, without delivering mail.

       With  Postfix  version  2.0  and	 earlier: the SMTP server delay	before
       sending a reject	(4xx or	5xx) response, when the	client has made	 fewer
       than $smtpd_soft_error_limit errors without delivering mail.

smtpd_etrn_restrictions	(default: empty)
       Optional	 SMTP  server  access  restrictions in the context of a	client
       ETRN request.

       The Postfix ETRN	implementation accepts only destinations that are eli-
       gible  for  the	Postfix	"fast flush" service. See the ETRN_README file
       for details.

       Specify a list of restrictions, separated by commas and/or  whitespace.
       Continue	 long  lines  by  starting the next line with whitespace.  Re-
       strictions are applied in the order as specified; the first restriction
       that matches wins.

       The  following restrictions are specific	to the domain name information
       received	with the ETRN command.

       check_etrn_access type:table
	      Search the specified access database for the ETRN	domain name or
	      its parent domains. See the access(5) manual page	for details.

       Other restrictions that are valid in this context:

       o      Generic  restrictions  that can be used in any SMTP command con-
	      text, described under smtpd_client_restrictions.

       o      SMTP   command	specific    restrictions    described	 under
	      smtpd_client_restrictions	and smtpd_helo_restrictions.

       Example:

       smtpd_etrn_restrictions = permit_mynetworks, reject

smtpd_expansion_filter (default: see postconf -d output)
       What characters are allowed in $name expansions of RBL reply templates.
       Characters not in the allowed set are replaced by "_".  Use C like  es-
       capes to	specify	special	characters such	as whitespace.

       This parameter is not subjected to $parameter expansion.

       This feature is available in Postfix 2.0	and later.

smtpd_forbidden_commands (default: CONNECT, GET, POST)
       List  of	 commands  that	 causes	the Postfix SMTP server	to immediately
       terminate 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, stress: 1)
       The  maximal  number  of	errors a remote	SMTP client is allowed to make
       without delivering mail.	The Postfix SMTP server	disconnects  when  the
       limit is	exceeded. Normally the default limit is	20, but	it changes un-
       der overload to just 1 with Postfix 2.6 and later.

smtpd_helo_required (default: no)
       Require that a remote SMTP client introduces itself at the beginning of
       an SMTP session with the	HELO or	EHLO command.

       Example:

       smtpd_helo_required = yes

smtpd_helo_restrictions	(default: empty)
       Optional	 restrictions that the Postfix SMTP server applies in the con-
       text of the SMTP	HELO command.

       The default is to permit	everything.

       Specify a list of restrictions, separated by commas and/or  whitespace.
       Continue	 long  lines  by  starting the next line with whitespace.  Re-
       strictions are applied in the order as specified; the first restriction
       that matches wins.

       The following restrictions are specific to the hostname information re-
       ceived with the HELO or EHLO command.

       check_helo_access type:table
	      Search the specified access(5) database for  the	HELO  or  EHLO
	      hostname	or  parent  domains, and execute the corresponding ac-
	      tion.

       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: a result of	"OK" is	not allowed for	 safety	 reasons.  In-
	      stead,  use DUNNO	in order to exclude specific hosts from	black-
	      lists.  This feature is available	in Postfix 2.1 and later.

       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: a result of	"OK" is	not allowed for	 safety	 reasons.  In-
	      stead,  use DUNNO	in order to exclude specific hosts from	black-
	      lists.  This feature is available	in Postfix 2.1 and later.

       reject_invalid_helo_hostname (with Postfix < 2.3:  reject_invalid_host-
       name)
	      Reject  the request when the HELO	or EHLO	hostname syntax	is in-
	      valid.
	      The invalid_hostname_reject_code specifies the response code for
	      rejected requests	(default: 501).

       reject_non_fqdn_helo_hostname	 (with	   Postfix    <	   2.3:	   re-
       ject_non_fqdn_hostname)
	      Reject the request when the HELO or  EHLO	 hostname  is  not  in
	      fully-qualified domain form, as required by the RFC.
	      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  hostname  is
	      listed  with  the	 A  record "d.d.d.d" under rbl_domain (Postfix
	      version 2.1 and later only).  If no "=d.d.d.d" is	specified, re-
	      ject  the	 request when the HELO or EHLO hostname	is listed with
	      any A record under rbl_domain.  See  the	reject_rbl_client  de-
	      scription	 for  additional RBL related configuration parameters.
	      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).

       Other restrictions that are valid in this context:

       o      Generic  restrictions  that can be used in any SMTP command con-
	      text, described under smtpd_client_restrictions.

       o      Client hostname or network  address  specific  restrictions  de-
	      scribed under smtpd_client_restrictions.

       o      SMTP    command	 specific    restrictions    described	 under
	      smtpd_sender_restrictions	or smtpd_recipient_restrictions.  When
	      sender or	recipient restrictions are listed under	smtpd_helo_re-
	      strictions, they have effect  only  with	"smtpd_delay_reject  =
	      yes",  so	that $smtpd_helo_restrictions is evaluated at the time
	      of the RCPT TO command.

       Examples:

       smtpd_helo_restrictions = permit_mynetworks, reject_invalid_helo_hostname
       smtpd_helo_restrictions = permit_mynetworks, reject_unknown_helo_hostname

smtpd_history_flush_threshold (default:	100)
       The maximal number of lines in the Postfix SMTP server command  history
       before it is flushed upon receipt of EHLO, RSET,	or end of DATA.

smtpd_junk_command_limit (default: normal: 100,	stress:	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  2.6
       and later.

smtpd_milters (default:	empty)
       A  list	of Milter (mail	filter)	applications for new mail that arrives
       via the Postfix smtpd(8)	server.	 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_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_timeout (default: 100s)
       The time	limit for connecting to	a proxy	filter and for sending or  re-
       ceiving information.  When a connection fails the client	gets a generic
       error message while more	detailed information is	logged to the  maillog
       file.

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

       This feature is available in Postfix 2.1	and later.

smtpd_recipient_limit (default:	1000)
       The maximal number of recipients	that the Postfix SMTP  server  accepts
       per message delivery request.

smtpd_recipient_overshoot_limit	(default: 1000)
       The  number  of recipients that a remote	SMTP client can	send in	excess
       of the limit specified with $smtpd_recipient_limit, before the  Postfix
       SMTP  server increments the per-session error count for each excess re-
       cipient.

smtpd_recipient_restrictions (default: permit_mynetworks, reject_unauth_desti-
       nation)
       The  access  restrictions  that	the Postfix SMTP server	applies	in the
       context of the RCPT TO command.

       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: If you change	this parameter setting,	you  must  specify  at
       least  one of the following restrictions. Otherwise Postfix will	refuse
       to receive mail:

	   reject, defer, defer_if_permit, reject_unauth_destination

       Specify a list of restrictions, separated by commas and/or  whitespace.
       Continue	 long  lines  by  starting the next line with whitespace.  Re-
       strictions are applied in the order as specified; the first restriction
       that matches wins.

       The  following  restrictions are	specific to the	recipient address that
       is received with	the RCPT TO command.

       check_recipient_access type:table
	      Search the specified access(5) database for the resolved RCPT TO
	      address,	domain,	parent domains,	or localpart@, and execute the
	      corresponding action.

       check_recipient_mx_access type:table
	      Search the specified access(5) database for the MX hosts for the
	      RCPT  TO	domain,	and execute the	corresponding action.  Note: a
	      result of	"OK" is	not allowed for	safety reasons.	 Instead,  use
	      DUNNO  in	order to exclude specific hosts	from blacklists.  This
	      feature is available in Postfix 2.1 and later.

       check_recipient_ns_access type:table
	      Search the specified access(5) database for the DNS servers  for
	      the RCPT TO domain, and execute the corresponding	action.	 Note:
	      a	result of "OK" is not allowed for safety reasons. Instead, use
	      DUNNO  in	order to exclude specific hosts	from blacklists.  This
	      feature is available in Postfix 2.1 and later.

       permit_auth_destination
	      Permit the request when one of the following is true:

       o      Postfix is mail forwarder: the resolved RCPT TO  domain  matches
	      $relay_domains  or a subdomain thereof, and the address contains
	      no sender-specified routing (user@elsewhere@domain),

       o      Postfix is the final destination:	the resolved  RCPT  TO	domain
	      matches	$mydestination,	 $inet_interfaces,  $proxy_interfaces,
	      $virtual_alias_domains, or $virtual_mailbox_domains, and the ad-
	      dress  contains  no sender-specified routing (user@elsewhere@do-
	      main).

       permit_mx_backup
	      Permit the request when the local	mail system is backup  MX  for
	      the RCPT TO domain, or when the domain is	an authorized destina-
	      tion (see	permit_auth_destination	for definition).

       o      Safety: permit_mx_backup does not	 accept	 addresses  that  have
	      sender-specified	 routing   information	 (example:  user@else-
	      where@domain).

       o      Safety: permit_mx_backup can be vulnerable to mis-use  when  ac-
	      cess is not restricted with permit_mx_backup_networks.

       o      Safety:  as  of  Postfix version 2.3, permit_mx_backup no	longer
	      accepts the address when the local mail system is	primary	MX for
	      the  recipient  domain.  Exception: permit_mx_backup accepts the
	      address when it specifies	an authorized  destination  (see  per-
	      mit_auth_destination for definition).

       o      Limitation:  mail	 may  be  rejected  in case of a temporary DNS
	      lookup problem with Postfix prior	to version 2.0.

       reject_non_fqdn_recipient
	      Reject the request when the RCPT TO address  is  not  in	fully-
	      qualified	domain form, as	required by the	RFC.
	      The  non_fqdn_reject_code	 parameter specifies the response code
	      for rejected requests (default: 504).

       reject_rhsbl_recipient rbl_domain=d.d.d.d
	      Reject the request when the RCPT TO domain is listed with	the  A
	      record "d.d.d.d" under rbl_domain	(Postfix version 2.1 and later
	      only).  If no "=d.d.d.d" is specified, reject the	 request  when
	      the RCPT TO domain is listed with	any A record under rbl_domain.
	      The  maps_rbl_reject_code	 parameter specifies the response code
	      for rejected requests (default: 554); the	default_rbl_reply  pa-
	      rameter  specifies  the  default	server	reply; and the rbl_re-
	      ply_maps parameter specifies tables with server replies  indexed
	      by rbl_domain.  This feature is available	in Postfix version 2.0
	      and later.

       reject_unauth_destination
	      Reject the request unless	one of the following is	true:

       o      Postfix is mail forwarder: the resolved RCPT TO  domain  matches
	      $relay_domains  or  a subdomain thereof, and contains no sender-
	      specified	routing	(user@elsewhere@domain),

       o      Postfix is the final destination:	the resolved  RCPT  TO	domain
	      matches	$mydestination,	 $inet_interfaces,  $proxy_interfaces,
	      $virtual_alias_domains, or  $virtual_mailbox_domains,  and  con-
	      tains no sender-specified	routing	(user@elsewhere@domain).
	       The  relay_domains_reject_code parameter	specifies the response
	      code for rejected	requests (default: 554).

       reject_unknown_recipient_domain
	      Reject the request when Postfix is not final destination for the
	      recipient	 domain,  and  the  RCPT  TO domain has	no DNS A or MX
	      record, or when it has a malformed MX record such	 as  a	record
	      with a zero-length MX hostname (Postfix version 2.3 and later).
	      The  unknown_address_reject_code parameter specifies the numeri-
	      cal response code	for rejected requests (default:	450).  The re-
	      sponse is	always 450 in case of a	temporary DNS error.
	      The  unknown_address_tempfail_action parameter specifies the ac-
	      tion after a temporary DNS error (default: defer_if_permit).

       reject_unlisted_recipient  (with	 Postfix  version  2.0:	 check_recipi-
       ent_maps)
	      Reject the request when the RCPT TO address is not listed	in the
	      list of valid recipients for its domain class. See the smtpd_re-
	      ject_unlisted_recipient parameter	description for	details.  This
	      feature is available in Postfix 2.1 and later.

       reject_unverified_recipient
	      Reject the request when mail to the RCPT TO address is known  to
	      bounce,  or when the recipient address destination is not	reach-
	      able.  Address verification information is managed by  the  ver-
	      ify(8)  server; see the ADDRESS_VERIFICATION_README file for de-
	      tails.
	      The unverified_recipient_reject_code parameter specifies the nu-
	      merical  response	 code  when an address is known	to bounce (de-
	      fault: 450, change into 550 when you are confident  that	it  is
	      safe to do so).
	      The  unverified_recipient_defer_code parameter specifies the nu-
	      merical response code when an address probe failed due to	a tem-
	      porary problem (default: 450).
	      The unverified_recipient_tempfail_action parameter specifies the
	      action after addres 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:

       smtpd_recipient_restrictions = permit_mynetworks, reject_unauth_destination

smtpd_reject_unlisted_recipient	(default: yes)
       Request that the	Postfix	SMTP server rejects mail for unknown recipient
       addresses,  even	 when no explicit reject_unlisted_recipient access re-
       striction is specified. This prevents the Postfix queue from filling up
       with undeliverable MAILER-DAEMON	messages.

       o      The recipient domain matches $mydestination, $inet_interfaces or
	      $proxy_interfaces, but the recipient is not listed in $local_re-
	      cipient_maps, and	$local_recipient_maps is not null.

       o      The  recipient domain matches $virtual_alias_domains but the re-
	      cipient is not listed in $virtual_alias_maps.

       o      The recipient domain matches  $virtual_mailbox_domains  but  the
	      recipient	 is  not  listed  in  $virtual_mailbox_maps, and $vir-
	      tual_mailbox_maps	is not null.

       o      The recipient domain matches $relay_domains but the recipient is
	      not  listed  in $relay_recipient_maps, and $relay_recipient_maps
	      is not null.

       This feature is available in Postfix 2.1	and later.

smtpd_reject_unlisted_sender (default: no)
       Request that the	Postfix	SMTP server rejects mail from  unknown	sender
       addresses, even when no explicit	reject_unlisted_sender access restric-
       tion is specified. This can slow	down an	explosion of forged mail  from
       worms or	viruses.

       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_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:

	   smtpd_recipient_restrictions	=
	       permit_mynetworks, permit_sasl_authenticated, ...

       To  reject  all	SMTP connections from unauthenticated clients, specify
       "smtpd_delay_reject = yes" (which is the	default) and use:

	   smtpd_client_restrictions = permit_sasl_authenticated, reject

       See the SASL_README file	for SASL configuration and operation details.

smtpd_sasl_authenticated_header	(default: no)
       Report the SASL authenticated user name in the smtpd(8)	Received  mes-
       sage header.

       This feature is available in Postfix 2.3	and later.

smtpd_sasl_exceptions_networks (default: empty)
       What  remote  SMTP  clients the Postfix SMTP server will	not offer AUTH
       support to.

       Some clients (Netscape 4	at least) have a bug that causes them  to  re-
       quire  a	login and password whenever AUTH is offered, whether it's nec-
       essary or not. To work around this, specify, for	 example,  $mynetworks
       to prevent Postfix from offering	AUTH to	local clients.

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

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

       Example:

       smtpd_sasl_exceptions_networks =	$mynetworks

       This feature is available in Postfix 2.1	and later.

smtpd_sasl_local_domain	(default: empty)
       The name	of the Postfix SMTP server's local SASL	authentication realm.

       By default, the local authentication realm name is the null string.

       Examples:

       smtpd_sasl_local_domain = $mydomain
       smtpd_sasl_local_domain = $myhostname

smtpd_sasl_path	(default: smtpd)
       Implementation-specific information that	the Postfix SMTP server	passes
       through	to  the	 SASL  plug-in	implementation	that  is selected with
       smtpd_sasl_type.	 Typically this	specifies the name of a	 configuration
       file or rendezvous point.

       This feature is available in Postfix 2.3	and later. In earlier releases
       it was called smtpd_sasl_application_name.

smtpd_sasl_security_options (default: noanonymous)
       Postfix SMTP server SASL	security options; as of	Postfix	2.3  the  list
       of available features depends on	the SASL server	implementation that is
       selected	with smtpd_sasl_type.

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

       Restrict	 what  authentication  mechanisms the Postfix SMTP server will
       offer to	the client.  The list of available  authentication  mechanisms
       is system dependent.

       Specify zero or more of the following:

       noplaintext
	      Disallow methods that use	plaintext passwords.

       noactive
	      Disallow methods subject to active (non-dictionary) attack.

       nodictionary
	      Disallow methods subject to passive (dictionary) attack.

       noanonymous
	      Disallow methods that allow anonymous authentication.

       forward_secrecy
	      Only allow methods that support forward secrecy (Dovecot only).

       mutual_auth
	      Only  allow  methods  that  provide  mutual  authentication (not
	      available	with Cyrus SASL	version	1).

       By default, the Postfix SMTP server accepts plaintext passwords but not
       anonymous logins.

       Warning:	 it appears that clients try authentication methods in the or-
       der as advertised by the	server (e.g., PLAIN ANONYMOUS CRAM-MD5)	 which
       means  that  if	you  disable  plaintext	passwords, clients will	log in
       anonymously, even when they should be able to use CRAM-MD5.  So,	if you
       disable plaintext logins, disable anonymous logins too.	Postfix	treats
       anonymous login as no authentication.

       Example:

       smtpd_sasl_security_options = noanonymous, noplaintext

smtpd_sasl_tls_security_options	(default: $smtpd_sasl_security_options)
       The SASL	authentication security	options	that the Postfix  SMTP	server
       uses for	TLS encrypted SMTP sessions.

       This feature is available in Postfix 2.2	and later.

smtpd_sasl_type	(default: cyrus)
       The  SASL  plug-in type that the	Postfix	SMTP server should use for au-
       thentication. The available types are listed  with  the	"postconf  -a"
       command.

       This feature is available in Postfix 2.3	and later.

smtpd_sender_login_maps	(default: empty)
       Optional	 lookup	 table with the	SASL login names that own sender (MAIL
       FROM) addresses.

       Specify zero or more "type:table" lookup	tables.	With lookups from  in-
       dexed  files  such  as DB or DBM, or from networked tables such as NIS,
       LDAP or SQL, the	following search operations are	done with a sender ad-
       dress of	user@domain:

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

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

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

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

smtpd_sender_restrictions (default: empty)
       Optional	restrictions that the Postfix SMTP server applies in the  con-
       text of the MAIL	FROM command.

       The default is to permit	everything.

       Specify	a list of restrictions,	separated by commas and/or whitespace.
       Continue	long lines by starting the next	 line  with  whitespace.   Re-
       strictions are applied in the order as specified; the first restriction
       that matches wins.

       The following restrictions are specific to the sender address  received
       with the	MAIL FROM command.

       check_sender_access type:table
	      Search  the  specified  access(5)	database for the MAIL FROM ad-
	      dress, domain, parent domains, or	localpart@,  and  execute  the
	      corresponding action.

       check_sender_mx_access type:table
	      Search the specified access(5) database for the MX hosts for the
	      MAIL FROM	address, and execute the corresponding action.	 Note:
	      a	result of "OK" is not allowed for safety reasons. Instead, use
	      DUNNO in order to	exclude	specific hosts from blacklists.	  This
	      feature is available in Postfix 2.1 and later.

       check_sender_ns_access type:table
	      Search  the specified access(5) database for the DNS servers for
	      the MAIL FROM address, and  execute  the	corresponding  action.
	      Note:  a	result	of "OK"	is not allowed for safety reasons. In-
	      stead, use DUNNO in order	to exclude specific hosts from	black-
	      lists.  This feature is available	in Postfix 2.1 and later.

       reject_authenticated_sender_login_mismatch
	      Enforces	the  reject_sender_login_mismatch  restriction for au-
	      thenticated clients only.	This feature is	available  in  Postfix
	      version 2.1 and later.

       reject_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).  If	no "=d.d.d.d" is specified, reject the request
	      when the MAIL FROM domain	is listed  with	 any  A	 record	 under
	      rbl_domain.
	      The  maps_rbl_reject_code	 parameter specifies the response code
	      for rejected requests (default:  554); the default_rbl_reply pa-
	      rameter  specifies  the  default	server	reply; and the rbl_re-
	      ply_maps parameter specifies tables with server replies  indexed
	      by  rbl_domain.	This  feature  is available in Postfix 2.0 and
	      later.

       reject_sender_login_mismatch
	      Reject the request when  $smtpd_sender_login_maps	 specifies  an
	      owner  for  the  MAIL FROM address, but the client is not	(SASL)
	      logged in	as that	MAIL FROM address owner; or when the client is
	      (SASL) logged in,	but the	client login name doesn't own the MAIL
	      FROM address according to	$smtpd_sender_login_maps.

       reject_unauthenticated_sender_login_mismatch
	      Enforces the reject_sender_login_mismatch	restriction for	 unau-
	      thenticated  clients  only. This feature is available in Postfix
	      version 2.1 and later.

       reject_unknown_sender_domain
	      Reject the request when Postfix is not final destination for the
	      sender  address,	and  the  MAIL FROM address has	no DNS A or MX
	      record, or when it has a malformed MX record such	 as  a	record
	      with a zero-length MX hostname (Postfix version 2.3 and later).
	      The  unknown_address_reject_code parameter specifies the numeri-
	      cal response code	for rejected requests (default:	450).  The re-
	      sponse is	always 450 in case of a	temporary DNS error.
	      The  unknown_address_tempfail_action parameter specifies the ac-
	      tion after a temporary DNS error (default: defer_if_permit).

       reject_unlisted_sender
	      Reject the request when the MAIL FROM address is not  listed  in
	      the  list	 of  valid  recipients	for  its domain	class. See the
	      smtpd_reject_unlisted_sender parameter description for  details.
	      This feature is available	in Postfix 2.1 and later.

       reject_unverified_sender
	      Reject  the  request when	mail to	the MAIL FROM address is known
	      to bounce, or when the sender address destination	is not	reach-
	      able.   Address  verification information	is managed by the ver-
	      ify(8) server; see the ADDRESS_VERIFICATION_README file for  de-
	      tails.
	      The unverified_sender_reject_code	parameter specifies the	numer-
	      ical response code when an address is known to bounce  (default:
	      450,  change  into 550 when you are confident that it is safe to
	      do so).
	      The unverified_sender_defer_code	specifies  the	numerical  re-
	      sponse code when an address address probe	failed due to a	tempo-
	      rary problem (default: 450).
	      The unverified_sender_tempfail_action  parameter	specifies  the
	      action  after  address  probe failure due	to a temporary problem
	      (default:	defer_if_permit).
	      This feature is available	in Postfix 2.1 and later.

       Other restrictions that are valid in this context:

       o      Generic restrictions that	can be used in any SMTP	 command  con-
	      text, described under smtpd_client_restrictions.

       o      SMTP    command	 specific    restrictions    described	 under
	      smtpd_client_restrictions	and smtpd_helo_restrictions.

       o      SMTP command specific restrictions described under smtpd_recipi-
	      ent_restrictions.	 When  recipient restrictions are listed under
	      smtpd_sender_restrictions, they have effect only with "smtpd_de-
	      lay_reject  = yes", so that $smtpd_sender_restrictions is	evalu-
	      ated at the time of the RCPT TO command.

       Examples:

       smtpd_sender_restrictions = reject_unknown_sender_domain
       smtpd_sender_restrictions = reject_unknown_sender_domain,
	   check_sender_access hash:/usr/local/etc/postfix/access

smtpd_soft_error_limit (default: 10)
       The number of errors a remote SMTP client is allowed  to	 make  without
       delivering  mail	 before	the Postfix SMTP server	slows down all its re-
       sponses.

       o      With Postfix version 2.1 and later, the Postfix SMTP server  de-
	      lays all responses by $smtpd_error_sleep_time seconds.

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

smtpd_starttls_timeout (default: 300s)
       The time	limit for Postfix SMTP server write and	read operations	during
       TLS startup and shutdown	handshake procedures.

       This feature is available in Postfix 2.2	and later.

smtpd_timeout (default:	normal:	300s, stress: 10s)
       The  time  limit	for sending a Postfix SMTP server response and for re-
       ceiving a remote	SMTP client request. Normally  the  default  limit  is
       300s,  but  it  changes under overload to just 10s with Postfix 2.6 and
       later.

       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)
       The file	with the certificate of	the certification authority (CA)  that
       issued  the  Postfix SMTP server	certificate.  This is needed only when
       the CA certificate is not already present  in  the  server  certificate
       file.   This file may also contain the CA certificates of other trusted
       CAs.  You must use this file for	the list of trusted CAs	if you want to
       use chroot-mode.

       Example:

       smtpd_tls_CAfile	= /usr/local/etc/postfix/CAcert.pem

       This feature is available in Postfix 2.2	and later.

smtpd_tls_CApath (default: empty)
       Directory  with	PEM format certificate authority certificates that the
       Postfix SMTP server offers to remote SMTP clients for  the  purpose  of
       client certificate verification.	 Do not	forget to create the necessary
       "hash" links with, for  example,	 "$OPENSSL_HOME/bin/c_rehash  /usr/lo-
       cal/etc/postfix/certs".

       To  use	this option in chroot mode, this directory (or a copy) must be
       inside the chroot jail. Please note that	in this	case the  CA  certifi-
       cates  are  not	offered	 to the	client,	so that	e.g.  Netscape clients
       might not offer certificates issued by them.  Use of  this  feature  is
       therefore not recommended.

       Example:

       smtpd_tls_CApath	= /usr/local/etc/postfix/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
       clients from caching sessions that almost certainly cannot be re-used.

       By  default,  the Postfix SMTP server always generates TLS session ids.
       This works around a known defect	in mail	client applications such as MS
       Outlook,	and may	also prevent interoperability issues with other	MTAs.

       Example:

       smtpd_tls_always_issue_session_ids = no

       This feature is available in Postfix 2.3	and later.

smtpd_tls_ask_ccert (default: no)
       Ask  a remote SMTP client for a client certificate. This	information is
       needed for certificate based mail relaying with,	for example, the  per-
       mit_tls_clientcerts feature.

       Some clients such as Netscape will either complain if no	certificate is
       available (for the list of CAs in $smtpd_tls_CAfile) or will offer mul-
       tiple client certificates to choose from. This may be annoying, so this
       option is "off" by default.

       This feature is available in Postfix 2.2	and later.

smtpd_tls_auth_only (default: no)
       When TLS	encryption is optional in the Postfix SMTP server, do not  an-
       nounce or accept	SASL authentication over unencrypted connections.

       This feature is available in Postfix 2.2	and later.

smtpd_tls_ccert_verifydepth (default: 9)
       The  verification depth for remote SMTP client certificates. A depth of
       1 is sufficient if the issuing CA is listed in a	local CA file.

       The default verification	depth is 9 (the	OpenSSL	default) for  compati-
       bility with earlier Postfix behavior. Prior to Postfix 2.5, the default
       value was 5, but	the limit was not actually enforced. If	you  have  set
       this  to	 a  lower  non-default	value,	certificates with longer trust
       chains may now fail to verify. Certificate chains with 1	or 2  CAs  are
       common,	deeper	chains	are  more  rare	and any	number between 5 and 9
       should suffice in practice. You can choose a lower number if, for exam-
       ple,  you  trust	 certificates directly signed by an issuing CA but not
       any CAs it delegates to.

       This feature is available in Postfix 2.2	and later.

smtpd_tls_cert_file (default: empty)
       File with the Postfix SMTP server RSA certificate in PEM	format.	  This
       file may	also contain the Postfix SMTP server private RSA key.

       Public  Internet	 MX hosts without certificates signed by a "reputable"
       CA must generate, and be	prepared to present to most clients,  a	 self-
       signed or private-CA signed certificate.	The client will	not be able to
       authenticate the	server,	but unless it is running Postfix 2.3 or	 simi-
       lar software, it	will still insist on a server certificate.

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

       Both RSA	and DSA	certificates  are  supported.	When  both  types  are
       present,	the cipher used	determines which certificate will be presented
       to the client.  For Netscape and	OpenSSL	clients	without	special	cipher
       choices the RSA certificate is preferred.

       In order	to verify a certificate, the CA	certificate (in	case of	a cer-
       tificate	chain, all CA certificates) must be available.	You should add
       these  certificates  to	the server certificate,	the server certificate
       first, then the issuing CA(s).

       Example:	the certificate	for "server.dom.ain" was issued	by "intermedi-
       ate  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 = /usr/local/etc/postfix/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: export)
       The minimum TLS cipher grade that the Postfix SMTP server will use with
       opportunistic  TLS  encryption.	Cipher	types  listed in smtpd_tls_ex-
       clude_ciphers are excluded from the base	definition of the selected ci-
       pher  grade. The	default	value "export" ensures maximum inter-operabil-
       ity. Because encryption is optional, stronger controls are  not	appro-
       priate, and this	setting	SHOULD NOT be changed unless the change	is es-
       sential.

       When  TLS  is  mandatory	 the  cipher   grade   is   chosen   via   the
       smtpd_tls_mandatory_ciphers configuration parameter, see	there for syn-
       tax details.

       Example:
       smtpd_tls_ciphers = export

       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 = /usr/local/etc/postfix/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
       EDH ciphers.

       Instead	of  using  the	exact  same parameter sets as distributed with
       other TLS packages, it is more secure to	generate your own set  of  pa-
       rameters	with something like the	following command:

	   openssl gendh -out /usr/local/etc/postfix/dh_1024.pem -2 1024

       Your  actual source for entropy may differ. Some	systems	have /dev/ran-
       dom; on other system you	may consider using the "Entropy	Gathering Dae-
       mon EGD", available at http://egd.sourceforge.net/

       Example:

       smtpd_tls_dh1024_param_file = /usr/local/etc/postfix/dh_1024.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
       EDH ciphers.

       See also	the discussion under the smtpd_tls_dh1024_param_file  configu-
       ration parameter.

       Example:

       smtpd_tls_dh512_param_file = /usr/local/etc/postfix/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 = /usr/local/etc/postfix/ecdsa-scert.pem

       This feature is available in Postfix 2.6	and  later,  when  Postfix  is
       compiled	and linked with	OpenSSL	0.9.9 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	0.9.9 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  official  Postfix  releases
	      (mail_version = major.minor.patchlevel).

       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 snapshot  releases	 (mail_version	=  ma-
	      jor.minor-releasedate).

       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.

       This feature is available in Postfix 2.6	and later, when	it is compiled
       and linked with OpenSSL 0.9.9 or	later.

smtpd_tls_exclude_ciphers (default: empty)
       List of ciphers or cipher types to exclude from the SMTP	server	cipher
       list at all TLS security	levels.	Excluding valid	ciphers	can create in-
       teroperability problems.	DO NOT exclude ciphers unless it is  essential
       to  do so. This is not an OpenSSL cipherlist; it	is a simple list sepa-
       rated by	whitespace and/or commas. The elements are a single cipher, or
       one or more "+" separated cipher	properties, in which case only ciphers
       matching	all the	properties are excluded.

       Examples	(some of these will cause problems):

	   smtpd_tls_exclude_ciphers = aNULL
	   smtpd_tls_exclude_ciphers = MD5, DES
	   smtpd_tls_exclude_ciphers = DES+MD5
	   smtpd_tls_exclude_ciphers = AES256-SHA, DES-CBC3-MD5
	   smtpd_tls_exclude_ciphers = kEDH+aRSA

       The first setting disables anonymous ciphers. The next setting disables
       ciphers	that  use the MD5 digest algorithm or the (single) DES encryp-
       tion algorithm. The next	setting	disables ciphers that use MD5 and  DES
       together.   The	next setting disables the two ciphers "AES256-SHA" and
       "DES-CBC3-MD5". The last	setting	disables ciphers that  use  "EDH"  key
       exchange	with RSA authentication.

       This feature is available in Postfix 2.3	and later.

smtpd_tls_fingerprint_digest (default: md5)
       The  message digest algorithm used to construct client-certificate fin-
       gerprints for check_ccert_access	and  permit_tls_clientcerts.  The  de-
       fault  algorithm	 is  md5, for backwards	compatibility with Postfix re-
       leases prior to 2.5.

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

       While  additional  digest algorithms are	often available	with OpenSSL's
       libcrypto, only those used by libssl in SSL cipher suites are available
       to Postfix. For now this	means just md5 or sha1.

       To find the fingerprint of a specific certificate file, with a specific
       digest algorithm, run:

	   $ openssl x509 -noout -fingerprint -digest -in certfile.pem

       The text	to the right of	"=" sign is the	desired	fingerprint.  For  ex-
       ample:

	   $ openssl x509 -noout -fingerprint -sha1 -in	cert.pem
	   SHA1	Fingerprint=D4:6A:AB:19:24:79:F8:32:BB:A6:CB:66:82:C0:8E:9B:EE:29:A8:1A

       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:/usr/local/etc/postfix/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 TLS	handshake and certificate information.

	      2	Log levels during TLS negotiation.

	      3	Log hexadecimal	and ASCII dump of TLS negotiation process.

	      4	 Also  log hexadecimal and ASCII dump of complete transmission
	      after STARTTLS.

       Use "smtpd_tls_loglevel = 3" only in case of problems. 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.  Cipher  types  listed  in  smtpd_tls_manda-
       tory_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 following cipher grades are supported:

       export Enable  the mainstream "EXPORT" grade or better OpenSSL ciphers.
	      This is the most appropriate setting for public MX hosts,	and is
	      always  used  with  opportunistic	TLS encryption.	The underlying
	      cipherlist is specified via the tls_export_cipherlist configura-
	      tion parameter, which you	are strongly encouraged	to not change.
	      The default value	of  tls_export_cipherlist  includes  anonymous
	      ciphers,	but these are automatically filtered out if the	server
	      is configured to ask for client certificates. If you must	always
	      exclude  anonymous ciphers, set "smtpd_tls_exclude_ciphers = aN-
	      ULL". To exclude anonymous ciphers only when  TLS	 is  enforced,
	      set "smtpd_tls_mandatory_exclude_ciphers = aNULL".

       low    Enable the mainstream "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. The default  value  of  tls_low_cipherlist  includes
	      anonymous	 ciphers,  but these are automatically filtered	out if
	      the server is configured to ask for client certificates. If  you
	      must   always  exclude  anonymous	 ciphers,  set	"smtpd_tls_ex-
	      clude_ciphers = aNULL". To exclude anonymous ciphers  only  when
	      TLS  is enforced,	set "smtpd_tls_mandatory_exclude_ciphers = aN-
	      ULL".

       medium Enable the mainstream "MEDIUM" grade or better OpenSSL  ciphers.
	      These  are  essentially the 128-bit or stronger ciphers. This is
	      the default minimum strength for mandatory TLS encryption.  MSAs
	      that  enforce  TLS  and  have  clients  that  do not support any
	      "MEDIUM" or "HIGH" grade ciphers,	may need to configure a	weaker
	      ("low"  or  "export")  minimum  cipher grade. The	underlying ci-
	      pherlist is specified via	the  tls_medium_cipherlist  configura-
	      tion parameter, which you	are strongly encouraged	to not change.
	      The default value	of  tls_medium_cipherlist  includes  anonymous
	      ciphers,	but these are automatically filtered out if the	server
	      is configured to ask for client certificates. If you must	always
	      exclude  anonymous ciphers, set "smtpd_tls_exclude_ciphers = aN-
	      ULL". To exclude anonymous ciphers only when  TLS	 is  enforced,
	      set "smtpd_tls_mandatory_exclude_ciphers = aNULL".

       high   Enable only the mainstream "HIGH"	grade OpenSSL ciphers. The un-
	      derlying cipherlist is  specified	 via  the  tls_high_cipherlist
	      configuration  parameter,	 which	you are	strongly encouraged to
	      not change. The default value  of	 tls_high_cipherlist  includes
	      anonymous	 ciphers,  but these are automatically filtered	out if
	      the server is configured to ask for client certificates. If  you
	      must   always  exclude  anonymous	 ciphers,  set	"smtpd_tls_ex-
	      clude_ciphers = aNULL". To exclude anonymous ciphers  only  when
	      TLS  is enforced,	set "smtpd_tls_mandatory_exclude_ciphers = aN-
	      ULL".

       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. The de-
	      fault value of tls_null_cipherlist  excludes  anonymous  ciphers
	      (OpenSSL	0.9.8 has NULL ciphers that offer data integrity with-
	      out encryption or	authentication).

       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  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:	SSLv3, TLSv1)
       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 supported
       protocol	 names are "SSLv2", "SSLv3" and	"TLSv1", and are not case sen-
       sitive.

       With Postfix >= 2.5 the parameter syntax	is expanded to support	proto-
       col  exclusions.	 One  can  now	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  still  sup-
       ported, use the form you	find more intuitive.

       Since  SSL  version  2  has known protocol weaknesses and is now	depre-
       cated, the default setting excludes "SSLv2".  This means	 that  by  de-
       fault, SSL version 2 will not be	used at	the "encrypt" security level.

       Example:

       smtpd_tls_mandatory_protocols = TLSv1
       # Alternative form with Postfix >= 2.5:
       smtpd_tls_mandatory_protocols = !SSLv2, !SSLv3

       This feature is available in Postfix 2.3	and later.

smtpd_tls_protocols (default: empty)
       List  of	TLS protocols that the Postfix SMTP server will	exclude	or in-
       clude with opportunistic	TLS encryption.	This parameter SHOULD be  left
       at  its default empty value, allowing all protocols to be used with op-
       portunistic TLS.

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

       To include a protocol list its name, to exclude	it,  prefix  the  name
       with  a	"!" character. To exclude SSLv2	even 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,	is supported, but not recommended. OpenSSL provides no
       mechanisms  for excluding protocols not known at	compile-time. If Post-
       fix is linked against an	OpenSSL	library	that supports additional  pro-
       tocol versions, they cannot be excluded using either syntax.

       Example:
       smtpd_tls_protocols = !SSLv2

       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 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	SMTP  clients,
	      but do not require that clients use TLS encryption.

       encrypt
	      Mandatory	 TLS  encryption:  announce  STARTTLS  support to SMTP
	      clients, and require that	clients	use TLS	encryption.  According
	      to  RFC 2487 this	MUST NOT be applied in case of a publicly-ref-
	      erenced 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 SMTP	client certificates, see TLS_README for	a dis-
       cussion	of  the	 smtpd_tls_ask_ccert,  smtpd_tls_req_ccert,  and  per-
       mit_tls_clientcerts features.

       Note  2:	The parameter setting "smtpd_tls_security_level	= encrypt" im-
       plies "smtpd_tls_auth_only = yes".

       Note 3: when invoked via	 "sendmail  -bs",  Postfix  will  never	 offer
       STARTTLS	 due  to  insufficient privileges to access the	server private
       key. This is intended behavior.

       This feature is available in Postfix 2.3	and later.

smtpd_tls_session_cache_database (default: empty)
       Name of the file	containing the optional	Postfix	SMTP server  TLS  ses-
       sion  cache. Specify a database type that supports enumeration, such as
       btree or	sdbm; there is no need to support concurrent access.  The file
       is  created if it does not exist. The smtpd(8) daemon does not use this
       parameter directly, rather the cache is implemented indirectly  in  the
       tlsmgr(8)  daemon.  This	 means that per-smtpd-instance master.cf over-
       rides of	this parameter are not effective. Note,	that each of the cache
       databases supported by tlsmgr(8)	daemon:	$smtpd_tls_session_cache_data-
       base, $smtp_tls_session_cache_database (and with	Postfix	2.3 and	 later
       $lmtp_tls_session_cache_database), needs	to be stored separately. It is
       not at this time	possible to store multiple caches in  a	 single	 data-
       base.

       Note:  dbm  databases  are  not	suitable.  TLS session objects are too
       large.

       As of version 2.5, Postfix no longer uses root privileges when  opening
       this  file.  The	 file  should  now  be	stored under the Postfix-owned
       data_directory. As a migration aid, an attempt to open the file under a
       non-Postfix  directory  is  redirected to the Postfix-owned data_direc-
       tory, and a warning is logged.

       Example:

       smtpd_tls_session_cache_database	= btree:/var/lib/postfix/smtpd_scache

       This feature is available in Postfix 2.2	and later.

smtpd_tls_session_cache_timeout	(default: 3600s)
       The expiration time of Postfix SMTP server TLS session  cache  informa-
       tion.  A	 cache cleanup is performed periodically every $smtpd_tls_ses-
       sion_cache_timeout seconds. As with  $smtpd_tls_session_cache_database,
       this  parameter	is  implemented	 in the	tlsmgr(8) daemon and therefore
       per-smtpd-instance master.cf overrides are not possible.

       This feature is available in Postfix 2.2	and later.

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_use_tls (default:	no)
       Opportunistic  TLS:  announce  STARTTLS support to 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,  and  pre-
       vents  the  Postfix  SMTP  server  from	rejecting mail permanently, by
       changing	5xx reply codes	into 4xx.  However, soft_bounce	is no cure for
       address rewriting mistakes or mail routing mistakes.

       Example:

       soft_bounce = yes

stale_lock_time	(default: 500s)
       The  time  after	 which	a stale	exclusive mailbox lockfile is removed.
       This is used for	delivery to file or mailbox.

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

stress (default: empty)
       This feature is documented in the STRESS_README document.

       This feature is available in Postfix 2.5	and later.

strict_7bit_headers (default: no)
       Reject  mail  with 8-bit	text in	message	headers. This blocks mail from
       poorly written applications.

       This feature should not be enabled on a general	purpose	 mail  server,
       because it is likely to reject legitimate email.

       This feature is available in Postfix 2.0	and later.

strict_8bitmime	(default: no)
       Enable both strict_7bit_headers and strict_8bitmime_body.

       This  feature  should  not be enabled on	a general purpose mail server,
       because it is likely to reject legitimate email.

       This feature is available in Postfix 2.0	and later.

strict_8bitmime_body (default: no)
       Reject 8-bit message body text without 8-bit MIME content encoding  in-
       formation.  This	blocks mail from poorly	written	applications.

       Unfortunately,  this  also rejects majordomo approval requests when the
       included	request	contains valid 8-bit MIME mail,	and it rejects bounces
       from  mailers  that do not MIME encapsulate 8-bit content (for example,
       bounces from qmail or from old versions of Postfix).

       This feature should not be enabled on a general	purpose	 mail  server,
       because it is likely to reject legitimate email.

       This feature is available in Postfix 2.0	and later.

strict_mailbox_ownership (default: yes)
       Defer  delivery when a mailbox file is not owned	by its recipient.  The
       default setting is not backwards	compatible.

       This feature is available in Postfix 2.5.3 and later.

strict_mime_encoding_domain (default: no)
       Reject mail with	invalid	Content-Transfer-Encoding: information for the
       message/*  or  multipart/*  MIME	 content types.	 This blocks mail from
       poorly written software.

       This feature should not be enabled on a general	purpose	 mail  server,
       because it will reject mail after a single violation.

       This feature is available in Postfix 2.0	and later.

strict_rfc821_envelopes	(default: no)
       Require	that addresses received	in SMTP	MAIL FROM and RCPT TO commands
       are enclosed with <>, and that those addresses do not contain  RFC  822
       style  comments	or phrases.  This stops	mail from poorly written soft-
       ware.

       By default, the Postfix SMTP server accepts RFC 822 syntax in MAIL FROM
       and RCPT	TO addresses.

sun_mailtool_compatibility (default: no)
       Obsolete	 SUN mailtool compatibility feature. Instead, use "mailbox_de-
       livery_lock = dotlock".

swap_bangpath (default:	yes)
       Enable the rewriting of "site!user" into	"user@site".  This  is	neces-
       sary  if	 your machine is connected to UUCP networks.  It is enabled by
       default.

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

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

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

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

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

       Example:

       swap_bangpath = no

syslog_facility	(default: mail)
       The  syslog  facility of	Postfix	logging. Specify a facility as defined
       in syslog.conf(5). The default facility is "mail".

       Warning:	a non-default syslog_facility setting takes effect only	 after
       a  Postfix process has completed	initialization.	 Errors	during process
       initialization will be logged with the default facility.	 Examples  are
       errors  while  parsing the command line arguments, and errors while ac-
       cessing the Postfix main.cf configuration file.

syslog_name (default: see postconf -d output)
       The mail	system name that is prepended to the process  name  in	syslog
       records,	so that	"smtpd"	becomes, for example, "postfix/smtpd".

       Warning:	 a  non-default	 syslog_name setting takes effect only after a
       Postfix process has completed  initialization.  Errors  during  process
       initialization  will  be	logged with the	default	name. Examples are er-
       rors while parsing the command line arguments, and errors while access-
       ing the Postfix main.cf configuration file.

tcp_windowsize (default: 0)
       An  optional  workaround	 for  routers  that  break TCP window scaling.
       Specify a value > 0 and < 65536 to enable this feature.	 With  Postfix
       TCP  servers  (smtpd(8),	 qmqpd(8)), this feature is implemented	by the
       Postfix master(8) daemon.

       To change this parameter	without	stopping Postfix, you  need  to	 first
       terminate all Postfix TCP servers:

	   # postconf -e master_service_disable=inet
	   # postfix reload

       This  immediately  terminates all processes that	accept network connec-
       tions.  Next, you enable	Postfix	TCP servers with the updated  tcp_win-
       dowsize setting:

	   # postconf -e tcp_windowsize=65535 master_service_disable=
	   # postfix reload

       If  you	skip  these  steps  with  a  running  Postfix system, then the
       tcp_windowsize change will work only for	Postfix	TCP clients  (smtp(8),
       lmtp(8)).

       This feature is available in Postfix 2.6	and later.

tls_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_eecdh_strong_curve (default: prime256v1)
       The elliptic  curve  used  by  the  SMTP	 server	 for  sensibly	strong
       ephemeral  ECDH	key  exchange.	This curve is used by the Postfix SMTP
       server when "smtpd_tls_eecdh_grade  =  strong".	The  phrase  "sensibly
       strong"	means  approximately  128-bit security based on	best known at-
       tacks. The selected curve must be implemented by	OpenSSL	 (as  reported
       by  ecparam(1) with the "-list_curves" option) and be one of the	curves
       listed in Section 5.1.1 of RFC 4492. You	should	not  generally	change
       this setting.

       This  default  curve  is	 specified  in NSA "Suite B" Cryptography (see
       http://www.nsa.gov/ia/industry/crypto_suite_b.cfm)   for	   information
       classified as 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.

       This feature is available in Postfix 2.6	and later, when	it is compiled
       and linked with OpenSSL 0.9.9 or	later.

tls_eecdh_ultra_curve (default:	secp384r1)
       The  elliptic  curve  used  by  the  SMTP  server  for maximally	strong
       ephemeral ECDH key exchange. This curve is used	by  the	 Postfix  SMTP
       server  when  "smtpd_tls_eecdh_grade  =	ultra".	 The phrase "maximally
       strong" means approximately 192-bit security based on  best  known  at-
       tacks.	This  additional strength comes	at a significant computational
       cost, most users	should instead set "smtpd_tls_eecdh_grade  =  strong".
       The  selected  curve must be implemented	by OpenSSL (as reported	by ec-
       param(1)	with the "-list_curves"	option)	 and  be  one  of  the	curves
       listed  in  Section  5.1.1 of RFC 4492. You should not generally	change
       this setting.

       This default "ultra" curve is specified in NSA "Suite  B"  Cryptography
       (see http://www.nsa.gov/ia/industry/crypto_suite_b.cfm) for information
       classified as TOP SECRET.

       This feature is available in Postfix 2.6	and later, when	it is compiled
       and linked with OpenSSL 0.9.9 or	later.

tls_export_cipherlist (default:	ALL:+RC4:@STRENGTH)
       The  OpenSSL  cipherlist	for "EXPORT" or	higher grade ciphers. This de-
       fines the meaning of the	"export"  setting  in  smtpd_tls_mandatory_ci-
       phers,  smtp_tls_mandatory_ciphers and lmtp_tls_mandatory_ciphers. This
       is the cipherlist for the opportunistic	("may")	 TLS  client  security
       level  and  is  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_mandatory_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_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_mandatory_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_medium_cipherlist (default:	ALL:!EXPORT:!LOW:+RC4:@STRENGTH)
       The OpenSSL cipherlist for "MEDIUM" or higher grade ciphers.  This  de-
       fines  the  meaning  of the "medium" setting in smtpd_tls_mandatory_ci-
       phers, smtp_tls_mandatory_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). 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_random_bytes (default: 32)
       The  number  of bytes that tlsmgr(8) reads from $tls_random_source when
       (re)seeding the in-memory pseudo	random number generator	 (PRNG)	 pool.
       The  default of 32 bytes	(256 bits) is good enough for 128bit symmetric
       keys.  If using EGD or a	device file, a maximum of 255 bytes is read.

       This feature is available in Postfix 2.2	and later.

tls_random_exchange_name (default: see postconf	-d output)
       Name of the pseudo random number	generator (PRNG) state	file  that  is
       maintained  by  tlsmgr(8).  The file is created when it does not	exist,
       and its length is fixed at 1024 bytes.

       As of version 2.5, Postfix no longer uses root privileges when  opening
       this  file, and the default file	location was changed from ${config_di-
       rectory}/prng_exch to ${data_directory}/prng_exch.  As a	migration aid,
       an attempt to open the file under a non-Postfix directory is redirected
       to the Postfix-owned data_directory, and	a warning is logged.

       This feature is available in Postfix 2.2	and later.

tls_random_prng_update_period (default:	3600s)
       The time	between	attempts by tlsmgr(8) to save the state	of the	pseudo
       random  number  generator  (PRNG)  to the file specified	with $tls_ran-
       dom_exchange_name.

       This feature is available in Postfix 2.2	and later.

tls_random_reseed_period (default: 3600s)
       The maximal time	between	attempts by tlsmgr(8) to re-seed the in-memory
       pseudo  random number generator (PRNG) pool from	external sources.  The
       actual time between re-seeding attempts is calculated using  the	 PRNG,
       and is between 0	and the	time specified.

       This feature is available in Postfix 2.2	and later.

tls_random_source (default: see	postconf -d output)
       The  external  entropy source for the in-memory tlsmgr(8) pseudo	random
       number generator	(PRNG) pool. Be	sure to	specify	a non-blocking source.
       If  this	 source	is not a regular file, the entropy source type must be
       prepended:  egd:/path/to/egd_socket for a source	 with  EGD  compatible
       socket interface, or dev:/path/to/device	for a device file.

       Note:  on  OpenBSD systems specify /dev/arandom when /dev/urandom gives
       timeout errors.

       This feature is available in Postfix 2.2	and later.

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.

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.

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.

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.

       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.

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.

       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.

       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.

       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.

transport_extra_recipient_limit	(default: $default_extra_recipient_limit)
       A transport-specific override for the default_extra_recipient_limit pa-
       rameter value, where transport is the master.cf name of the message de-
       livery transport.

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.

       This feature is available in Postfix 2.5	and later.

transport_maps (default: empty)
       Optional	lookup tables with mappings from recipient address to (message
       delivery	transport, next-hop destination).  See	transport(5)  for  de-
       tails.

       Specify	zero or	more "type:table" lookup tables.  If you use this fea-
       ture with local files, run  "postmap  /usr/local/etc/postfix/transport"
       after making a change.

       For safety reasons, as of Postfix 2.3 this feature does not allow $num-
       ber substitutions in regular expression maps.

       Examples:

       transport_maps =	dbm:/usr/local/etc/postfix/transport
       transport_maps =	hash:/usr/local/etc/postfix/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.

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.

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.

       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.

       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.

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:	To: undisclosed-recipients:;)
       Message	header	that the Postfix cleanup(8) server inserts when	a mes-
       sage contains no	To: or Cc: message header. With	Postfix	2.4 and	later,
       specify an empty	value to disable this feature.

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

       Do not change this unless you have  a  complete	understanding  of  RFC
       2821.

unknown_address_tempfail_action	(default: $reject_tempfail_action)
       The  Postfix  SMTP server's action when reject_unknown_sender_domain or
       reject_unknown_recipient_domain fail due	to a  temporary	 error	condi-
       tion.  Specify  "defer" to defer	the remote SMTP	client request immedi-
       ately. With the default	"defer_if_permit"  action,  the	 Postfix  SMTP
       server  continues  to look for opportunities to reject mail, and	defers
       the client request only if it would otherwise be	accepted.

       This feature is available in Postfix 2.6	and later.

unknown_client_reject_code (default: 450)
       The numerical Postfix SMTP server response code when a  client  without
       valid   address	 <=>  name  mapping  is	 rejected  by  the  reject_un-
       known_client_hostname restriction. The SMTP server always replies  with
       450 when	the mapping failed due to a temporary error condition.

       Do  not	change	this  unless  you have a complete understanding	of RFC
       2821.

unknown_helo_hostname_tempfail_action (default:	$reject_tempfail_action)
       The Postfix  SMTP  server's  action  when  reject_unknown_helo_hostname
       fails due to an temporary error condition. Specify "defer" to defer the
       remote SMTP client request immediately. With the	default	"defer_if_per-
       mit"  action,  the Postfix SMTP server continues	to look	for opportuni-
       ties to reject mail, and	defers the client request  only	 if  it	 would
       otherwise be accepted.

       This feature is available in Postfix 2.6	and later.

unknown_hostname_reject_code (default: 450)
       The numerical Postfix SMTP server response code when the	hostname spec-
       ified with the HELO or EHLO  command  is	 rejected  by  the  reject_un-
       known_helo_hostname restriction.

       Do  not	change	this  unless  you have a complete understanding	of RFC
       2821.

unknown_local_recipient_reject_code (default: 550)
       The numerical Postfix SMTP server response code when  a	recipient  ad-
       dress  is  local,  and $local_recipient_maps specifies a	list of	lookup
       tables that does	not match the recipient.  A recipient address is local
       when  its domain	matches	$mydestination,	$proxy_interfaces or $inet_in-
       terfaces.

       The default setting is 550 (reject mail)	but it is safer	 to  initially
       use  450	 (try  again  later)  so you have time to find out if your lo-
       cal_recipient_maps settings are OK.

       Example:

       unknown_local_recipient_reject_code = 450

       This feature is available in Postfix 2.0	and later.

unknown_relay_recipient_reject_code (default: 550)
       The numerical Postfix SMTP server reply code when a  recipient  address
       matches	$relay_domains,	 and  relay_recipient_maps specifies a list of
       lookup tables that does not match the recipient address.

       This feature is available in Postfix 2.0	and later.

unknown_virtual_alias_reject_code (default: 550)
       The SMTP	server reply code  when	 a  recipient  address	matches	 $vir-
       tual_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 SMTP	server reply code  when	 a  recipient  address	matches	 $vir-
       tual_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
       2821.

       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
       2821.

       This feature is available in Postfix 2.1	and later.

unverified_recipient_reject_reason (default: empty)
       The Postfix SMTP	server's reply when rejecting mail with	reject_unveri-
       fied_recipient.	Do  not	include	the numeric SMTP reply code or the en-
       hanced status code. By default, the response  includes  actual  address
       verification details.

       Example:

       unverified_recipient_reject_reason = Recipient address lookup failed

       This feature is available in Postfix 2.6	and later.

unverified_recipient_tempfail_action (default: $reject_tempfail_action)
       The Postfix SMTP	server's action	when reject_unverified_recipient fails
       due to a	temporary error	condition. Specify "defer" to defer the	remote
       SMTP client request immediately.	With the default "defer_if_permit" ac-
       tion, the Postfix SMTP server continues to look	for  opportunities  to
       reject  mail,  and defers the client request only if it would otherwise
       be accepted.

       This feature is available in Postfix 2.6	and later.

unverified_sender_defer_code (default: 450)
       The numerical Postfix SMTP server response code when a  sender  address
       probe fails due to a temporary error condition.

       Unlike elsewhere	in Postfix, you	can specify 250	in order to accept the
       address anyway.

       Do not change this unless you have  a  complete	understanding  of  RFC
       2821.

       This feature is available in Postfix 2.6	and later.

unverified_sender_reject_code (default:	450)
       The  numerical  Postfix	SMTP server response code when a recipient ad-
       dress is	rejected by the	reject_unverified_sender restriction.

       Unlike elsewhere	in Postfix, you	can specify 250	in order to accept the
       address anyway.

       Do  not	change	this  unless  you have a complete understanding	of RFC
       2821.

       This feature is available in Postfix 2.1	and later.

unverified_sender_reject_reason	(default: empty)
       The Postfix SMTP	server's reply when rejecting mail with	reject_unveri-
       fied_sender. Do not include the numeric SMTP reply code or the enhanced
       status code. By default,	the response includes actual address verifica-
       tion details.

       Example:

       unverified_sender_reject_reason = Sender	address	lookup failed

       This feature is available in Postfix 2.6	and later.

unverified_sender_tempfail_action (default: $reject_tempfail_action)
       The  Postfix  SMTP  server's action when	reject_unverified_sender fails
       due to a	temporary error	condition. Specify "defer" to defer the	remote
       SMTP client request immediately.	With the default "defer_if_permit" ac-
       tion, the Postfix SMTP server continues to look	for  opportunities  to
       reject  mail,  and defers the client request only if it would otherwise
       be accepted.

       This feature is available in Postfix 2.6	and later.

verp_delimiter_filter (default:	-=+)
       The characters Postfix accepts as  VERP	delimiter  characters  on  the
       Postfix sendmail(1) command line	and in SMTP commands.

       This feature is available in Postfix 1.1	and later.

virtual_alias_domains (default:	$virtual_alias_maps)
       Postfix	is  final  destination for the specified list of virtual alias
       domains,	that is, domains for which all addresses are  aliased  to  ad-
       dresses in other	local or remote	domains. The SMTP server validates re-
       cipient addresses with $virtual_alias_maps and rejects non-existent re-
       cipients.   See	also  the  virtual  alias  domain  class  in  the  AD-
       DRESS_CLASS_README file

       This feature is available in Postfix 2.0	and later. The	default	 value
       is backwards compatible with Postfix version 1.1.

       The  default  value is $virtual_alias_maps so that you can keep all in-
       formation about virtual alias domains in	one place.  If you  have  many
       users,  it  is  better  to  separate information	that changes more fre-
       quently (virtual	address	-> local or remote address mapping)  from  in-
       formation  that	changes	 less  frequently  (the	list of	virtual	domain
       names).

       Specify a list of host or domain	names,	"/file/name"  or  "type:table"
       patterns, separated by commas and/or whitespace.	A "/file/name" pattern
       is replaced by its contents; a "type:table"  lookup  table  is  matched
       when  a	table  entry matches a lookup string (the lookup result	is ig-
       nored).	Continue long lines by starting	the next line with whitespace.
       Specify	"!pattern" to exclude a	host or	domain name from the list. The
       form "!/file/name" is supported only in Postfix version 2.4 and later.

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

       Example:

       virtual_alias_domains = virtual1.tld virtual2.tld

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

       This feature is available in Postfix 2.1	and later.

virtual_alias_maps (default: $virtual_maps)
       Optional	lookup tables that alias specific mail addresses or domains to
       other  local or remote address.	The table format and lookups are docu-
       mented in virtual(5). For an overview of	Postfix	address	 manipulations
       see the ADDRESS_REWRITING_README	document.

       This  feature  is available in Postfix 2.0 and later. The default value
       is backwards compatible with Postfix version 1.1.

       If you use this feature	with  indexed  files,  run  "postmap  /usr/lo-
       cal/etc/postfix/virtual"	after changing the file.

       Examples:

       virtual_alias_maps = dbm:/usr/local/etc/postfix/virtual
       virtual_alias_maps = hash:/usr/local/etc/postfix/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.

       In  a  lookup table, specify a left-hand	side of	"@domain.tld" to match
       any user	in  the	 specified  domain  that  does	not  have  a  specific
       "user@domain.tld" entry.

       When   a	  recipient   address	has   an  optional  address  extension
       (user+foo@domain.tld), the virtual(8) delivery agent looks up the  full
       address	first,	and  when the lookup fails, it looks up	the unextended
       address (user@domain.tld).

       Note 1: for security reasons, the virtual(8) delivery  agent  disallows
       regular expression substitution of $1 etc. in regular expression	lookup
       tables, because that would open a security hole.

       Note 2: for  security  reasons,	the  virtual(8)	 delivery  agent  will
       silently	ignore requests	to use the proxymap(8) server. Instead it will
       open the	table directly.	Before Postfix version 2.2, the	virtual(8) de-
       livery agent will terminate with	a fatal	error.

virtual_mailbox_base (default: empty)
       A  prefix  that	the virtual(8) delivery	agent prepends to all pathname
       results from $virtual_mailbox_maps table	lookups.   This	 is  a	safety
       measure	to  ensure  that an out	of control map doesn't litter the file
       system with mailboxes.  While virtual_mailbox_base could	be set to "/",
       this setting isn't recommended.

       Example:

       virtual_mailbox_base = /var/mail

virtual_mailbox_domains	(default: $virtual_mailbox_maps)
       Postfix is final	destination for	the specified list of domains; mail is
       delivered via the $virtual_transport mail delivery transport.   By  de-
       fault  this  is the Postfix virtual(8) delivery agent.  The SMTP	server
       validates recipient addresses with  $virtual_mailbox_maps  and  rejects
       mail  for non-existent recipients.  See also the	virtual	mailbox	domain
       class in	the ADDRESS_CLASS_README file.

       This parameter expects the same syntax as the mydestination  configura-
       tion parameter.

       This  feature  is available in Postfix 2.0 and later. The default value
       is backwards compatible with Postfix version 1.1.

virtual_mailbox_limit (default:	51200000)
       The maximal size	in bytes of an individual mailbox or maildir file,  or
       zero (no	limit).

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

       Note 1: the dotlock method requires that	the recipient UID or  GID  has
       write access to the parent directory of the recipient's mailbox file.

       Note 2: the default setting of this parameter is	system dependent.

virtual_mailbox_maps (default: empty)
       Optional	 lookup	 tables	 with  all valid addresses in the domains that
       match $virtual_mailbox_domains.

       In a lookup table, specify a left-hand side of "@domain.tld"  to	 match
       any  user  in  the  specified  domain  that  does  not  have a specific
       "user@domain.tld" entry.

       The virtual(8) delivery agent uses this table to	look up	the per-recip-
       ient mailbox or maildir pathname.  If the lookup	result ends in a slash
       ("/"), maildir-style delivery is	carried	out, otherwise the path	is as-
       sumed  to  specify a UNIX-style mailbox file.  Note that	$virtual_mail-
       box_base	is unconditionally prepended to	this path.

       When  a	recipient  address   has   an	optional   address   extension
       (user+foo@domain.tld),  the virtual(8) delivery agent looks up the full
       address first, and when the lookup fails, it looks  up  the  unextended
       address (user@domain.tld).

       Note  1:	 for security reasons, the virtual(8) delivery agent disallows
       regular expression substitution of $1 etc. in regular expression	lookup
       tables, because that would open a security hole.

       Note  2:	 for  security	reasons,  the  virtual(8)  delivery agent will
       silently	ignore requests	to use the proxymap(8) server. Instead it will
       open the	table directly.	Before Postfix version 2.2, the	virtual(8) de-
       livery agent will terminate with	a fatal	error.

virtual_maps (default: empty)
       Optional	lookup tables with a) names of domains for which all addresses
       are  aliased  to	addresses in other local or remote domains, and	b) ad-
       dresses that are	aliased	to addresses in	other local or remote domains.
       Available  before  Postfix  version  2.0.  With Postfix version 2.0 and
       later, this is replaced by separate controls: virtual_alias_domains and
       virtual_alias_maps.

virtual_minimum_uid (default: 100)
       The minimum user	ID value that the virtual(8) delivery agent accepts as
       a result	from $virtual_uid_maps table  lookup.	Returned  values  less
       than this will be rejected, and the message will	be deferred.

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
       part is optional.  For more details see the transport(5)	manual page.

       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.

       In a lookup table, specify a left-hand side of "@domain.tld"  to	 match
       any  user  in  the  specified  domain  that  does  not  have a specific
       "user@domain.tld" entry.

       When  a	recipient  address   has   an	optional   address   extension
       (user+foo@domain.tld),  the virtual(8) delivery agent looks up the full
       address first, and when the lookup fails, it looks  up  the  unextended
       address (user@domain.tld).

       Note  1:	 for security reasons, the virtual(8) delivery agent disallows
       regular expression substitution of $1 etc. in regular expression	lookup
       tables, because that would open a security hole.

       Note  2:	 for  security	reasons,  the  virtual(8)  delivery agent will
       silently	ignore requests	to use the proxymap(8) server. Instead it will
       open the	table directly.	Before Postfix version 2.2, the	virtual(8) de-
       livery agent will terminate with	a fatal	error.

SEE ALSO
       postconf(1), Postfix configuration parameter maintenance
       master(5), Postfix daemon configuration maintenance

LICENSE
       The Secure Mailer license must be distributed with this software.

AUTHOR(S)
       Wietse Venema
       IBM T.J.	Watson Research
       P.O. Box	704
       Yorktown	Heights, NY 10598, USA

								   POSTCONF(5)

NAME | SYNOPSIS | DESCRIPTION | 2bounce_notice_recipient (default: postmaster) | access_map_defer_code (default: 450) | access_map_reject_code (default: 554) | address_verify_default_transport (default: $default_transport) | address_verify_local_transport (default: $local_transport) | address_verify_map (default: empty) | 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: 3) | 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_relayhost_maps (default: $sender_dependent_re- | 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_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_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_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) | dont_remove (default: 0) | double_bounce_sender (default: double-bounce) | duplicate_filter_limit (default: 1000) | empty_address_recipient (default: MAILER-DAEMON) | empty_address_relayhost_maps_lookup_key (default: <>) | enable_errors_to (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: ipv4) | 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) | lmtp_bind_address (default: empty) | lmtp_bind_address6 (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_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_enforce_tls (default: no) | lmtp_generic_maps (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_mx_address_limit (default: 5) | lmtp_mx_session_limit (default: 2) | 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_rset_timeout (default: 20s) | lmtp_sasl_auth_cache_name (default: empty) | lmtp_sasl_auth_cache_time (default: 90d) | lmtp_sasl_auth_enable (default: no) | lmtp_sasl_auth_soft_bounce (default: yes) | lmtp_sasl_mechanism_filter (default: empty) | lmtp_sasl_password_maps (default: empty) | lmtp_sasl_path (default: empty) | lmtp_sasl_security_options (default: noplaintext, noanonymous) | lmtp_sasl_tls_security_options (default: $lmtp_sasl_security_options) | lmtp_sasl_tls_verified_security_options (default: $lmtp_sasl_tls_security_op- | lmtp_sasl_type (default: cyrus) | lmtp_send_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_cert_file (default: empty) | lmtp_tls_ciphers (default: export) | 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_key_file (default: $lmtp_tls_cert_file) | lmtp_tls_loglevel (default: 0) | lmtp_tls_mandatory_ciphers (default: empty) | lmtp_tls_mandatory_exclude_ciphers (default: empty) | lmtp_tls_mandatory_protocols (default: SSLv3, TLSv1) | lmtp_tls_note_starttls_offer (default: no) | lmtp_tls_per_site (default: empty) | lmtp_tls_policy_maps (default: empty) | lmtp_tls_protocols (default: empty) | 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_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_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: 2) | 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) | 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_fudge_factor (default: 100) | 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) | 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_relayhost_maps (default: empty) | 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_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_reuse_limit (default: 10) | smtp_connection_cache_time_limit (default: 2s) | 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_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: 990) | 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_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_rset_timeout (default: 20s) | smtp_sasl_auth_cache_name (default: empty) | smtp_sasl_auth_cache_time (default: 90d) | smtp_sasl_auth_enable (default: no) | smtp_sasl_auth_soft_bounce (default: yes) | smtp_sasl_mechanism_filter (default: empty) | smtp_sasl_password_maps (default: empty) | smtp_sasl_path (default: empty) | smtp_sasl_security_options (default: noplaintext, noanonymous) | smtp_sasl_tls_security_options (default: $smtp_sasl_security_options) | smtp_sasl_tls_verified_security_options (default: $smtp_sasl_tls_security_op- | smtp_sasl_type (default: cyrus) | smtp_send_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_cert_file (default: empty) | smtp_tls_cipherlist (default: empty) | smtp_tls_ciphers (default: export) | 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_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: SSLv3, TLSv1) | smtp_tls_note_starttls_offer (default: no) | smtp_tls_per_site (default: empty) | smtp_tls_policy_maps (default: empty) | smtp_tls_protocols (default: empty) | 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_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_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, stress: 1) | smtpd_helo_required (default: no) | smtpd_helo_restrictions (default: empty) | smtpd_history_flush_threshold (default: 100) | smtpd_junk_command_limit (default: normal: 100, stress: 1) | smtpd_milters (default: empty) | smtpd_noop_commands (default: empty) | smtpd_null_access_lookup_key (default: <>) | smtpd_peername_lookup (default: 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_timeout (default: 100s) | smtpd_recipient_limit (default: 1000) | smtpd_recipient_overshoot_limit (default: 1000) | smtpd_recipient_restrictions (default: permit_mynetworks, reject_unauth_desti- | smtpd_reject_unlisted_recipient (default: yes) | smtpd_reject_unlisted_sender (default: no) | 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_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_soft_error_limit (default: 10) | smtpd_starttls_timeout (default: 300s) | smtpd_timeout (default: normal: 300s, stress: 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: export) | 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: SSLv3, TLSv1) | smtpd_tls_protocols (default: empty) | 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_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_daemon_random_bytes (default: 32) | 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_low_cipherlist (default: ALL:!EXPORT:+RC4:@STRENGTH) | tls_medium_cipherlist (default: ALL:!EXPORT:!LOW:+RC4:@STRENGTH) | tls_null_cipherlist (default: eNULL:!aNULL) | 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) | 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: To: undisclosed-recipients:;) | 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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