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SMTP(8)			    System Manager's Manual		       SMTP(8)

NAME
       smtp - Postfix SMTP+LMTP	client

SYNOPSIS
       smtp [generic Postfix daemon options]

DESCRIPTION
       The Postfix SMTP+LMTP client implements the SMTP	and LMTP mail delivery
       protocols. It processes message delivery	requests from the  queue  man-
       ager.  Each  request specifies a	queue file, a sender address, a	domain
       or host to deliver to, and recipient information.  This program expects
       to be run from the master(8) process manager.

       The  SMTP+LMTP  client  updates	the queue file and marks recipients as
       finished, or it informs the queue manager that delivery should be tried
       again  at  a  later  time.  Delivery  status  reports  are  sent	to the
       bounce(8), defer(8) or trace(8) daemon as appropriate.

       The SMTP+LMTP client looks up a list of mail  exchanger	addresses  for
       the  destination	 host,	sorts  the list	by preference, and connects to
       each listed address until it finds a server that	responds.

       When a server is	not reachable, or when mail delivery fails  due	 to  a
       recoverable  error  condition, the SMTP+LMTP client will	try to deliver
       the mail	to an alternate	host.

       After a successful mail transaction, a connection may be	saved  to  the
       scache(8)  connection  cache  server,  so  that	it  may	be used	by any
       SMTP+LMTP client	for a subsequent transaction.

       By default, connection caching is enabled temporarily for  destinations
       that have a high	volume of mail in the active queue. Connection caching
       can be enabled permanently for specific destinations.

SMTP DESTINATION SYNTAX
       SMTP destinations have the following form:

       domainname

       domainname:port
	      Look up the mail exchangers for the specified domain,  and  con-
	      nect to the specified port (default: smtp).

       [hostname]

       [hostname]:port
	      Look  up	the  address(es) of the	specified host,	and connect to
	      the specified port (default: smtp).

       [address]

       [address]:port
	      Connect to the host at the specified address, and	connect	to the
	      specified	 port (default:	smtp). An IPv6 address must be format-
	      ted as [ipv6:address].

LMTP DESTINATION SYNTAX
       LMTP destinations have the following form:

       unix:pathname
	      Connect to the local UNIX-domain server that  is	bound  to  the
	      specified	 pathname.  If	the process runs chrooted, an absolute
	      pathname is interpreted relative to the Postfix queue directory.

       inet:hostname

       inet:hostname:port

       inet:[address]

       inet:[address]:port
	      Connect to the specified TCP port	on the specified local or  re-
	      mote  host. If no	port is	specified, connect to the port defined
	      as lmtp in services(4).	If  no	such  service  is  found,  the
	      lmtp_tcp_port configuration parameter (default value of 24) will
	      be used.	An IPv6	address	must be	formatted as [ipv6:address].

SECURITY
       The SMTP+LMTP client is moderately security-sensitive. It talks to SMTP
       or LMTP servers and to DNS servers on the network. The SMTP+LMTP	client
       can be run chrooted at fixed low	privilege.

STANDARDS
       RFC 821 (SMTP protocol)
       RFC 822 (ARPA Internet Text Messages)
       RFC 1651	(SMTP service extensions)
       RFC 1652	(8bit-MIME transport)
       RFC 1870	(Message Size Declaration)
       RFC 2033	(LMTP protocol)
       RFC 2034	(SMTP Enhanced Error Codes)
       RFC 2045	(MIME: Format of Internet Message Bodies)
       RFC 2046	(MIME: Media Types)
       RFC 2554	(AUTH command)
       RFC 2821	(SMTP protocol)
       RFC 2920	(SMTP Pipelining)
       RFC 3207	(STARTTLS command)
       RFC 3461	(SMTP DSN Extension)
       RFC 3463	(Enhanced Status Codes)
       RFC 4954	(AUTH command)
       RFC 5321	(SMTP protocol)

DIAGNOSTICS
       Problems	and transactions are logged to syslogd(8).  Corrupted  message
       files are marked	so that	the queue manager can move them	to the corrupt
       queue for further inspection.

       Depending on the	setting	of the notify_classes parameter, the  postmas-
       ter is notified of bounces, protocol problems, and of other trouble.

BUGS
       SMTP  and LMTP connection caching does not work with TLS. The necessary
       support for TLS object passivation and  re-activation  does  not	 exist
       without closing the session, which defeats the purpose.

       SMTP  and  LMTP	connection  caching  assumes that SASL credentials are
       valid for all destinations that map onto	the same IP  address  and  TCP
       port.

CONFIGURATION PARAMETERS
       Before  Postfix version 2.3, the	LMTP client is a separate program that
       implements only a subset	of  the	 functionality	available  with	 SMTP:
       there  is  no  support  for TLS,	and connections	are cached in-process,
       making it ineffective when the client is	used for multiple domains.

       Most smtp_xxx configuration parameters have an lmtp_xxx "mirror"	param-
       eter  for  the  equivalent  LMTP	 feature. This document	describes only
       those LMTP-related parameters that aren't simply	"mirror" parameters.

       Changes to main.cf are picked up	automatically,	as  smtp(8)  processes
       run for only a limited amount of	time. Use the command "postfix reload"
       to speed	up a change.

       The text	below provides only a parameter	summary. See  postconf(5)  for
       more details including examples.

COMPATIBILITY CONTROLS
       ignore_mx_lookup_error (no)
	      Ignore DNS MX lookups that produce no response.

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

       smtp_never_send_ehlo (no)
	      Never send EHLO at the start of an SMTP session.

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

       smtp_line_length_limit (998)
	      The maximal length of message header and body lines that Postfix
	      will send	via SMTP.

       smtp_pix_workaround_delay_time (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.

       smtp_pix_workaround_threshold_time (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.

       smtp_pix_workarounds (disable_esmtp, delay_dotcrlf)
	      A	list that specifies zero or more  workarounds  for  CISCO  PIX
	      firewall bugs.

       smtp_pix_workaround_maps	(empty)
	      Lookup  tables,  indexed by the remote SMTP server address, with
	      per-destination workarounds for CISCO PIX	firewall bugs.

       smtp_quote_rfc821_envelope (yes)
	      Quote addresses in Postfix SMTP client MAIL  FROM	 and  RCPT  TO
	      commands as required by RFC 5321.

       smtp_reply_filter (empty)
	      A	 mechanism  to	transform replies from remote SMTP servers one
	      line at a	time.

       smtp_skip_5xx_greeting (yes)
	      Skip remote SMTP servers that greet with a 5XX status code.

       smtp_skip_quit_response (yes)
	      Do not wait for the response to the SMTP QUIT command.

       Available in Postfix version 2.0	and earlier:

       smtp_skip_4xx_greeting (yes)
	      Skip SMTP	servers	that greet with	a 4XX status  code  (go	 away,
	      try again	later).

       Available in Postfix version 2.2	and later:

       smtp_discard_ehlo_keyword_address_maps (empty)
	      Lookup  tables,  indexed by the remote SMTP server address, with
	      case insensitive lists of	EHLO keywords  (pipelining,  starttls,
	      auth, etc.) that the Postfix SMTP	client will ignore in the EHLO
	      response from a remote SMTP server.

       smtp_discard_ehlo_keywords (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.

       smtp_generic_maps (empty)
	      Optional lookup tables that perform  address  rewriting  in  the
	      Postfix  SMTP client, typically to transform a locally valid ad-
	      dress into a globally valid address when sending mail across the
	      Internet.

       Available in Postfix version 2.2.9 and later:

       smtp_cname_overrides_servername (version	dependent)
	      Allow  DNS  CNAME	 records  to  override the servername that the
	      Postfix SMTP client uses for logging, SASL password lookup,  TLS
	      policy decisions,	or TLS certificate verification.

       Available in Postfix version 2.3	and later:

       lmtp_discard_lhlo_keyword_address_maps (empty)
	      Lookup  tables,  indexed by the remote LMTP server address, with
	      case insensitive lists of	LHLO keywords  (pipelining,  starttls,
	      auth, etc.) that the Postfix LMTP	client will ignore in the LHLO
	      response from a remote LMTP server.

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

       Available in Postfix version 2.4.4 and later:

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

       Available in Postfix version 2.5	and later:

       smtp_header_checks (empty)
	      Restricted header_checks(5) tables for the Postfix SMTP client.

       smtp_mime_header_checks (empty)
	      Restricted  mime_header_checks(5)	 tables	 for  the Postfix SMTP
	      client.

       smtp_nested_header_checks (empty)
	      Restricted nested_header_checks(5) tables	for the	 Postfix  SMTP
	      client.

       smtp_body_checks	(empty)
	      Restricted body_checks(5)	tables for the Postfix SMTP client.

       Available in Postfix version 2.6	and later:

       tcp_windowsize (0)
	      An  optional  workaround for routers that	break TCP window scal-
	      ing.

       Available in Postfix version 2.8	and later:

       smtp_dns_resolver_options (empty)
	      DNS Resolver options for the Postfix SMTP	client.

       Available in Postfix version 2.9	and later:

       smtp_per_record_deadline	(no)
	      Change the behavior of the smtp_*_timeout	time  limits,  from  a
	      time  limit  per	read  or write system call, to a time limit to
	      send or receive a	complete record	(an SMTP  command  line,  SMTP
	      response	line,  SMTP message content line, or TLS protocol mes-
	      sage).

       smtp_send_dummy_mail_auth (no)
	      Whether or not to	append the "AUTH=<>" option to the  MAIL  FROM
	      command in SASL-authenticated SMTP sessions.

       Available in Postfix version 2.11 and later:

       smtp_dns_support_level (empty)
	      Level of DNS support in the Postfix SMTP client.

MIME PROCESSING	CONTROLS
       Available in Postfix version 2.0	and later:

       disable_mime_output_conversion (no)
	      Disable the conversion of	8BITMIME format	to 7BIT	format.

       mime_boundary_length_limit (2048)
	      The maximal length of MIME multipart boundary strings.

       mime_nesting_limit (100)
	      The maximal recursion level that the MIME	processor will handle.

EXTERNAL CONTENT INSPECTION CONTROLS
       Available in Postfix version 2.1	and later:

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

SASL AUTHENTICATION CONTROLS
       smtp_sasl_auth_enable (no)
	      Enable SASL authentication in the	Postfix	SMTP client.

       smtp_sasl_password_maps (empty)
	      Optional Postfix	SMTP  client  lookup  tables  with  one	 user-
	      name:password entry per remote hostname or domain, or sender ad-
	      dress when sender-dependent authentication is enabled.

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

       Available in Postfix version 2.2	and later:

       smtp_sasl_mechanism_filter (empty)
	      If non-empty, a Postfix SMTP client filter for the  remote  SMTP
	      server's list of offered SASL mechanisms.

       Available in Postfix version 2.3	and later:

       smtp_sender_dependent_authentication (no)
	      Enable  sender-dependent	authentication	in  the	 Postfix  SMTP
	      client; this is available	only  with  SASL  authentication,  and
	      disables	SMTP  connection caching to ensure that	mail from dif-
	      ferent senders will use the appropriate credentials.

       smtp_sasl_path (empty)
	      Implementation-specific information that the Postfix SMTP	client
	      passes  through  to  the SASL plug-in implementation that	is se-
	      lected with smtp_sasl_type.

       smtp_sasl_type (cyrus)
	      The SASL plug-in type that the Postfix SMTP  client  should  use
	      for authentication.

       Available in Postfix version 2.5	and later:

       smtp_sasl_auth_cache_name (empty)
	      An  optional table to prevent repeated SASL authentication fail-
	      ures with	the same remote	SMTP  server  hostname,	 username  and
	      password.

       smtp_sasl_auth_cache_time (90d)
	      The  maximal age of an smtp_sasl_auth_cache_name entry before it
	      is removed.

       smtp_sasl_auth_soft_bounce (yes)
	      When a remote SMTP server	rejects	a SASL authentication  request
	      with  a 535 reply	code, defer mail delivery instead of returning
	      mail as undeliverable.

       Available in Postfix version 2.9	and later:

       smtp_send_dummy_mail_auth (no)
	      Whether or not to	append the "AUTH=<>" option to the  MAIL  FROM
	      command in SASL-authenticated SMTP sessions.

STARTTLS SUPPORT CONTROLS
       Detailed	 information  about STARTTLS configuration may be found	in the
       TLS_README document.

       smtp_tls_security_level (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_en-
	      force_peername.

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

       smtp_starttls_timeout (300s)
	      Time limit for Postfix SMTP client  write	 and  read  operations
	      during TLS startup and shutdown handshake	procedures.

       smtp_tls_CAfile (empty)
	      A	 file  containing  CA certificates of root CAs trusted to sign
	      either remote SMTP server	certificates or	intermediate  CA  cer-
	      tificates.

       smtp_tls_CApath (empty)
	      Directory	 with  PEM  format  certificate	authority certificates
	      that the Postfix SMTP client uses	to verify a remote SMTP	server
	      certificate.

       smtp_tls_cert_file (empty)
	      File with	the Postfix SMTP client	RSA certificate	in PEM format.

       smtp_tls_mandatory_ciphers (medium)
	      The  minimum  TLS	cipher grade that the Postfix SMTP client will
	      use with mandatory TLS encryption.

       smtp_tls_exclude_ciphers	(empty)
	      List of ciphers or cipher	types to exclude from the Postfix SMTP
	      client cipher list at all	TLS security levels.

       smtp_tls_mandatory_exclude_ciphers (empty)
	      Additional  list	of ciphers or cipher types to exclude from the
	      Postfix SMTP client cipher list at mandatory TLS	security  lev-
	      els.

       smtp_tls_dcert_file (empty)
	      File with	the Postfix SMTP client	DSA certificate	in PEM format.

       smtp_tls_dkey_file ($smtp_tls_dcert_file)
	      File with	the Postfix SMTP client	DSA private key	in PEM format.

       smtp_tls_key_file ($smtp_tls_cert_file)
	      File with	the Postfix SMTP client	RSA private key	in PEM format.

       smtp_tls_loglevel (0)
	      Enable additional	Postfix	SMTP client logging of TLS activity.

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

       smtp_tls_policy_maps (empty)
	      Optional lookup tables with the Postfix SMTP client TLS security
	      policy by	next-hop destination; when a non-empty value is	speci-
	      fied, this overrides the obsolete	smtp_tls_per_site parameter.

       smtp_tls_mandatory_protocols (!SSLv2, !SSLv3)
	      List of SSL/TLS protocols	that the Postfix SMTP client will  use
	      with mandatory TLS encryption.

       smtp_tls_scert_verifydepth (9)
	      The verification depth for remote	SMTP server certificates.

       smtp_tls_secure_cert_match (nexthop, dot-nexthop)
	      How  the	Postfix	 SMTP  client  verifies	the server certificate
	      peername for the "secure"	TLS security level.

       smtp_tls_session_cache_database (empty)
	      Name of the file containing the optional Postfix SMTP client TLS
	      session cache.

       smtp_tls_session_cache_timeout (3600s)
	      The expiration time of Postfix SMTP client TLS session cache in-
	      formation.

       smtp_tls_verify_cert_match (hostname)
	      How the Postfix SMTP  client  verifies  the  server  certificate
	      peername for the "verify"	TLS security level.

       tls_daemon_random_bytes (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).

       tls_high_cipherlist (ALL:!EXPORT:!LOW:!MEDIUM:+RC4:@STRENGTH)
	      The OpenSSL cipherlist for "HIGH"	grade ciphers.

       tls_medium_cipherlist (ALL:!EXPORT:!LOW:+RC4:@STRENGTH)
	      The OpenSSL cipherlist for "MEDIUM" or higher grade ciphers.

       tls_low_cipherlist (ALL:!EXPORT:+RC4:@STRENGTH)
	      The OpenSSL cipherlist for "LOW" or higher grade ciphers.

       tls_export_cipherlist (ALL:+RC4:@STRENGTH)
	      The OpenSSL cipherlist for "EXPORT" or higher grade ciphers.

       tls_null_cipherlist (eNULL:!aNULL)
	      The OpenSSL cipherlist for "NULL"	grade ciphers that provide au-
	      thentication without encryption.

       Available in Postfix version 2.4	and later:

       smtp_sasl_tls_verified_security_options	  ($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 certificate.

       Available in Postfix version 2.5	and later:

       smtp_tls_fingerprint_cert_match (empty)
	      List  of	acceptable remote SMTP server certificate fingerprints
	      for  the	"fingerprint"  TLS  security   level   (smtp_tls_secu-
	      rity_level = fingerprint).

       smtp_tls_fingerprint_digest (md5)
	      The  message  digest  algorithm  used  to	 construct remote SMTP
	      server certificate fingerprints.

       Available in Postfix version 2.6	and later:

       smtp_tls_protocols (!SSLv2, !SSLv3)
	      List of TLS protocols that the Postfix SMTP client will  exclude
	      or include with opportunistic TLS	encryption.

       smtp_tls_ciphers	(medium)
	      The  minimum  TLS	cipher grade that the Postfix SMTP client will
	      use with opportunistic TLS encryption.

       smtp_tls_eccert_file (empty)
	      File with	the Postfix SMTP client	ECDSA certificate in PEM  for-
	      mat.

       smtp_tls_eckey_file ($smtp_tls_eccert_file)
	      File  with the Postfix SMTP client ECDSA private key in PEM for-
	      mat.

       Available in Postfix version 2.7	and later:

       smtp_tls_block_early_mail_reply (no)
	      Try to detect a mail hijacking attack based on  a	 TLS  protocol
	      vulnerability  (CVE-2009-3555), where an attacker	prepends mali-
	      cious HELO, MAIL,	RCPT, DATA commands to a Postfix  SMTP	client
	      TLS session.

       Available in Postfix version 2.8	and later:

       tls_disable_workarounds (see 'postconf -d' output)
	      List or bit-mask of OpenSSL bug work-arounds to disable.

       Available in Postfix version 2.11 and later:

       smtp_tls_trust_anchor_file (empty)
	      Zero  or	more  PEM-format  files	with trust-anchor certificates
	      and/or public keys.

       smtp_tls_force_insecure_host_tlsa_lookup	(no)
	      Lookup the associated DANE TLSA RRset even when  a  hostname  is
	      not an alias and its address records lie in an unsigned zone.

       tls_dane_trust_anchor_digest_enable (yes)
	      RFC 6698 trust-anchor digest support in the Postfix TLS library.

       tlsmgr_service_name (tlsmgr)
	      The name of the tlsmgr(8)	service	entry in master.cf.

OBSOLETE STARTTLS CONTROLS
       The  following  configuration  parameters  exist	for compatibility with
       Postfix versions	before 2.3. Support for	these will be removed in a fu-
       ture release.

       smtp_use_tls (no)
	      Opportunistic  mode: use TLS when	a remote SMTP server announces
	      STARTTLS support,	otherwise send the mail	in the clear.

       smtp_enforce_tls	(no)
	      Enforcement mode:	require	that remote SMTP servers use  TLS  en-
	      cryption,	and never send mail in the clear.

       smtp_tls_enforce_peername (yes)
	      With  mandatory  TLS  encryption,	 require  that the remote SMTP
	      server hostname matches  the  information	 in  the  remote  SMTP
	      server certificate.

       smtp_tls_per_site (empty)
	      Optional	lookup	tables	with the Postfix SMTP client TLS usage
	      policy by	next-hop destination and by remote SMTP	 server	 host-
	      name.

       smtp_tls_cipherlist (empty)
	      Obsolete	Postfix	 < 2.3 control for the Postfix SMTP client TLS
	      cipher list.

RESOURCE AND RATE CONTROLS
       smtp_destination_concurrency_limit	 ($default_destination_concur-
       rency_limit)
	      The  maximal  number of parallel deliveries to the same destina-
	      tion via the smtp	message	delivery transport.

       smtp_destination_recipient_limit	($default_destination_recipient_limit)
	      The maximal number of recipients per message for the  smtp  mes-
	      sage delivery transport.

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

       smtp_helo_timeout (300s)
	      The Postfix SMTP client time limit for sending the HELO or  EHLO
	      command,	and  for  receiving the	initial	remote SMTP server re-
	      sponse.

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

       smtp_xforward_timeout (300s)
	      The Postfix SMTP client time limit for sending the XFORWARD com-
	      mand, and	for receiving the remote SMTP server response.

       smtp_mail_timeout (300s)
	      The Postfix SMTP client time limit for  sending  the  MAIL  FROM
	      command, and for receiving the remote SMTP server	response.

       smtp_rcpt_timeout (300s)
	      The  Postfix SMTP	client time limit for sending the SMTP RCPT TO
	      command, and for receiving the remote SMTP server	response.

       smtp_data_init_timeout (120s)
	      The Postfix SMTP client time limit for  sending  the  SMTP  DATA
	      command, and for receiving the remote SMTP server	response.

       smtp_data_xfer_timeout (180s)
	      The  Postfix SMTP	client time limit for sending the SMTP message
	      content.

       smtp_data_done_timeout (600s)
	      The Postfix SMTP client time limit for sending the SMTP ".", and
	      for receiving the	remote SMTP server response.

       smtp_quit_timeout (300s)
	      The Postfix SMTP client time limit for sending the QUIT command,
	      and for receiving	the remote SMTP	server response.

       Available in Postfix version 2.1	and later:

       smtp_mx_address_limit (5)
	      The maximal number of MX (mail exchanger)	IP addresses that  can
	      result  from Postfix SMTP	client mail exchanger lookups, or zero
	      (no limit).

       smtp_mx_session_limit (2)
	      The maximal number of SMTP sessions per delivery request	before
	      the  Postfix SMTP	client gives up	or delivers to a fall-back re-
	      lay host,	or zero	(no limit).

       smtp_rset_timeout (20s)
	      The Postfix SMTP client time limit for sending the RSET command,
	      and for receiving	the remote SMTP	server response.

       Available in Postfix version 2.2	and earlier:

       lmtp_cache_connection (yes)
	      Keep  Postfix  LMTP  client connections open for up to $max_idle
	      seconds.

       Available in Postfix version 2.2	and later:

       smtp_connection_cache_destinations (empty)
	      Permanently enable SMTP connection  caching  for	the  specified
	      destinations.

       smtp_connection_cache_on_demand (yes)
	      Temporarily  enable  SMTP	connection caching while a destination
	      has a high volume	of mail	in the active queue.

       smtp_connection_reuse_time_limit	(300s)
	      The amount of time during	which Postfix will use an SMTP connec-
	      tion repeatedly.

       smtp_connection_cache_time_limit	(2s)
	      When SMTP	connection caching is enabled, the amount of time that
	      an unused	SMTP client socket is kept open	before it is closed.

       Available in Postfix version 2.3	and later:

       connection_cache_protocol_timeout (5s)
	      Time limit for connection	cache connect, send or receive	opera-
	      tions.

       Available in Postfix version 2.9	and later:

       smtp_per_record_deadline	(no)
	      Change  the  behavior  of	the smtp_*_timeout time	limits,	from a
	      time limit per read or write system call,	to  a  time  limit  to
	      send  or	receive	 a complete record (an SMTP command line, SMTP
	      response line, SMTP message content line,	or TLS	protocol  mes-
	      sage).

       Available in Postfix version 2.11 and later:

       smtp_connection_reuse_count_limit (0)
	      When  SMTP  connection  caching  is enabled, the number of times
	      that an SMTP session may be reused before	it is closed, or  zero
	      (no limit).

TROUBLE	SHOOTING CONTROLS
       debug_peer_level	(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 (empty)
	      Optional list of remote client or	server hostname	or network ad-
	      dress  patterns that cause the verbose logging level to increase
	      by the amount specified in $debug_peer_level.

       error_notice_recipient (postmaster)
	      The recipient of postmaster notifications	 about	mail  delivery
	      problems that are	caused by policy, resource, software or	proto-
	      col errors.

       internal_mail_filter_classes (empty)
	      What categories of Postfix-generated mail	are subject to before-
	      queue content inspection by non_smtpd_milters, header_checks and
	      body_checks.

       notify_classes (resource, software)
	      The list of error	classes	that are reported to the postmaster.

MISCELLANEOUS CONTROLS
       best_mx_transport (empty)
	      Where the	Postfix	SMTP client should deliver mail	 when  it  de-
	      tects a "mail loops back to myself" error	condition.

       config_directory	(see 'postconf -d' output)
	      The  default  location of	the Postfix main.cf and	master.cf con-
	      figuration files.

       daemon_timeout (18000s)
	      How much time a Postfix daemon process may take to handle	a  re-
	      quest before it is terminated by a built-in watchdog timer.

       delay_logging_resolution_limit (2)
	      The  maximal  number of digits after the decimal point when log-
	      ging sub-second delay values.

       disable_dns_lookups (no)
	      Disable DNS lookups in the Postfix SMTP and LMTP clients.

       inet_interfaces (all)
	      The network interface addresses that this	mail  system  receives
	      mail on.

       inet_protocols (all)
	      The  Internet  protocols Postfix will attempt to use when	making
	      or accepting connections.

       ipc_timeout (3600s)
	      The time limit for sending or receiving information over an  in-
	      ternal communication channel.

       lmtp_assume_final (no)
	      When  a remote LMTP server announces no DSN support, assume that
	      the server performs final	delivery, and send "delivered"	deliv-
	      ery status notifications instead of "relayed".

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

       max_idle	(100s)
	      The  maximum  amount of time that	an idle	Postfix	daemon process
	      waits for	an incoming connection before terminating voluntarily.

       max_use (100)
	      The maximal number of incoming connections that a	Postfix	daemon
	      process will service before terminating voluntarily.

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

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

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

       smtp_address_preference (any)
	      The address type ("ipv6",	"ipv4" or "any") that the Postfix SMTP
	      client  will try first, when a destination has IPv6 and IPv4 ad-
	      dresses with equal MX preference.

       smtp_bind_address (empty)
	      An optional numerical network  address  that  the	 Postfix  SMTP
	      client should bind to when making	an IPv4	connection.

       smtp_bind_address6 (empty)
	      An  optional  numerical  network	address	 that the Postfix SMTP
	      client should bind to when making	an IPv6	connection.

       smtp_helo_name ($myhostname)
	      The hostname to send in the SMTP EHLO or HELO command.

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

       smtp_host_lookup	(dns)
	      What mechanisms the Postfix SMTP client uses to look up a	host's
	      IP address.

       smtp_randomize_addresses	(yes)
	      Randomize	the order of equal-preference MX host addresses.

       syslog_facility (mail)
	      The syslog facility of Postfix logging.

       syslog_name (see	'postconf -d' output)
	      The  mail	 system	 name that is prepended	to the process name in
	      syslog records, so that "smtpd"  becomes,	 for  example,	"post-
	      fix/smtpd".

       Available with Postfix 2.2 and earlier:

       fallback_relay (empty)
	      Optional list of relay hosts for SMTP destinations that can't be
	      found or that are	unreachable.

       Available with Postfix 2.3 and later:

       smtp_fallback_relay ($fallback_relay)
	      Optional list of relay hosts for SMTP destinations that can't be
	      found or that are	unreachable.

SEE ALSO
       generic(5), output address rewriting
       header_checks(5), message header	content	inspection
       body_checks(5), body parts content inspection
       qmgr(8),	queue manager
       bounce(8), delivery status reports
       scache(8), connection cache server
       postconf(5), configuration parameters
       master(5), generic daemon options
       master(8), process manager
       tlsmgr(8), TLS session and PRNG management
       syslogd(8), system logging

README FILES
       Use  "postconf readme_directory"	or "postconf html_directory" to	locate
       this information.
       SASL_README, Postfix SASL howto
       TLS_README, Postfix STARTTLS howto

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

       Command pipelining in cooperation with:
       Jon Ribbens
       Oaktree Internet	Solutions Ltd.,
       Internet	House,
       Canal Basin,
       Coventry,
       CV1 4LY,	United Kingdom.

       SASL support originally by:
       Till Franke
       SuSE Rhein/Main AG
       65760 Eschborn, Germany

       TLS support originally by:
       Lutz Jaenicke
       BTU Cottbus
       Allgemeine Elektrotechnik
       Universitaetsplatz 3-4
       D-03044 Cottbus,	Germany

       Revised TLS and SMTP connection cache support by:
       Victor Duchovni
       Morgan Stanley

								       SMTP(8)

NAME | SYNOPSIS | DESCRIPTION | SMTP DESTINATION SYNTAX | LMTP DESTINATION SYNTAX | SECURITY | STANDARDS | DIAGNOSTICS | BUGS | CONFIGURATION PARAMETERS | COMPATIBILITY CONTROLS | MIME PROCESSING CONTROLS | EXTERNAL CONTENT INSPECTION CONTROLS | SASL AUTHENTICATION CONTROLS | STARTTLS SUPPORT CONTROLS | OBSOLETE STARTTLS CONTROLS | RESOURCE AND RATE CONTROLS | TROUBLE SHOOTING CONTROLS | MISCELLANEOUS CONTROLS | SEE ALSO | README FILES | LICENSE | AUTHOR(S)

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