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



NAME
       smtpd - Postfix SMTP server

SYNOPSIS
       smtpd [generic Postfix daemon options]

DESCRIPTION
       The  SMTP  server accepts network connection requests and performs zero
       or more SMTP transactions per connection.   Each  received  message  is
       piped  through  the  cleanup(8) daemon, and is placed into the incoming
       queue as one single queue file.  For this mode of operation,  the  pro-
       gram expects to be run from the master(8) process manager.

       Alternatively, the SMTP server takes an established connection on stan-
       dard input and deposits messages directly into the maildrop  queue.  In
       this  so-called  stand-alone mode, the SMTP server can accept mail even
       while the mail system is not running.

       The SMTP  server  implements  a  variety  of  policies  for  connection
       requests,  and  for parameters given to HELO, ETRN, MAIL FROM, VRFY and
       RCPT TO commands. They are detailed below and in the main.cf configura-
       tion file.

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

STANDARDS
       RFC 821 (SMTP protocol)
       RFC 1123 (Host requirements)
       RFC 1652 (8bit-MIME transport)
       RFC 1869 (SMTP service extensions)
       RFC 1870 (Message Size Declaration)
       RFC 1985 (ETRN command)
       RFC 2554 (AUTH command)
       RFC 2821 (SMTP protocol)
       RFC 2920 (SMTP Pipelining)

DIAGNOSTICS
       Problems and transactions are logged to syslogd(8).

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

CONFIGURATION PARAMETERS
       Changes  to  main.cf are picked up automatically, as smtpd(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
       The following parameters work around  implementation  errors  in  other
       software,  and/or  allow  you to override standards in order to prevent
       undesirable use.

       broken_sasl_auth_clients (no)
              Enable inter-operability with SMTP  clients  that  implement  an
              obsolete version of the AUTH command (RFC 2554).

       disable_vrfy_command (no)
              Disable the SMTP VRFY command.

       smtpd_noop_commands (empty)
              List  of  commands  that the Postfix SMTP server replies to with
              "250 Ok", without doing any syntax checks and  without  changing
              state.

       strict_rfc821_envelopes (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.

       Available in Postfix version 2.1 and later:

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

       smtpd_reject_unlisted_sender (no)
              Request  that  the Postfix SMTP server rejects mail from unknown
              sender addresses, even when no  explicit  reject_unlisted_sender
              access restriction is specified.

       smtpd_sasl_exceptions_networks (empty)
              What SMTP clients Postfix will not offer AUTH support to.

AFTER QUEUE EXTERNAL CONTENT INSPECTION CONTROLS
       As  of  version  1.0,  Postfix can be configured to send new mail to an
       external content filter AFTER the mail is queued. This  content  filter
       is  expected to inject mail back into a (Postfix or other) MTA for fur-
       ther delivery. See the FILTER_README document for details.

       content_filter (empty)
              The name of a mail delivery transport that filters mail after it
              is queued.

BEFORE QUEUE EXTERNAL CONTENT INSPECTION CONTROLS
       As  of  version  2.1, the Postfix SMTP server can be configured to send
       incoming mail to a real-time SMTP-based content filter BEFORE  mail  is
       queued.  This content filter is expected to inject mail back into Post-
       fix.  See the SMTPD_PROXY_README document for details on how to config-
       ure and operate this feature.

       smtpd_proxy_filter (empty)
              The hostname and TCP port of the mail filtering proxy server.

       smtpd_proxy_ehlo ($myhostname)
              How  the  Postfix SMTP server announces itself to the proxy fil-
              ter.

       smtpd_proxy_timeout (100s)
              The time limit for connecting to a proxy filter and for  sending
              or receiving information.

GENERAL CONTENT INSPECTION CONTROLS
       The  following parameters are applicable for both built-in and external
       content filters.

       Available in Postfix version 2.1 and later:

       receive_override_options (empty)
              Enable or disable recipient validation, built-in content filter-
              ing, or address rewriting.

EXTERNAL CONTENT INSPECTION CONTROLS
       The  following  parameters  are  applicable  for  both before-queue and
       after-queue content filtering.

       Available in Postfix version 2.1 and later:

       smtpd_authorized_xforward_hosts (empty)
              What SMTP clients are allowed to use the XFORWARD feature.

SASL AUTHENTICATION CONTROLS
       Postfix SASL support (RFC 2554) can be used to authenticate remote SMTP
       clients  to  the  Postfix  SMTP server, and to authenticate the Postfix
       SMTP client to a remote SMTP server.  See the SASL_README document  for
       details.

       broken_sasl_auth_clients (no)
              Enable  inter-operability  with  SMTP  clients that implement an
              obsolete version of the AUTH command (RFC 2554).

       smtpd_sasl_auth_enable (no)
              Enable SASL authentication in the Postfix SMTP server.

       smtpd_sasl_application_name (smtpd)
              The application name used for SASL server initialization.

       smtpd_sasl_local_domain (empty)
              The name of the local SASL authentication realm.

       smtpd_sasl_security_options (noanonymous)
              Restrict what authentication mechanisms the Postfix SMTP  server
              will offer to the client.

       smtpd_sender_login_maps (empty)
              Optional  lookup table with the SASL login names that own sender
              (MAIL FROM) addresses.

       Available in Postfix version 2.1 and later:

       smtpd_sasl_exceptions_networks (empty)
              What SMTP clients Postfix will not offer AUTH support to.

VERP SUPPORT CONTROLS
       With VERP style delivery, each recipient of a message receives  a  cus-
       tomized  copy of the message with his/her own recipient address encoded
       in the envelope sender address.  The VERP_README file describes config-
       uration  and operation details of Postfix support for variable envelope
       return path addresses.  VERP style delivery is requested with the  SMTP
       XVERP  command  or  with  the  "sendmail -V" command-line option and is
       available in Postfix version 1.1 and later.

       default_verp_delimiters (+=)
              The two default VERP delimiter characters.

       verp_delimiter_filter (-=+)
              The characters Postfix accepts as VERP delimiter  characters  on
              the Postfix sendmail(1) command line and in SMTP commands.

       Available in Postfix version 1.1 and 2.0:

       authorized_verp_clients ($mynetworks)
              What SMTP clients are allowed to specify the XVERP command.

       Available in Postfix version 2.1 and later:

       smtpd_authorized_verp_clients ($authorized_verp_clients)
              What SMTP clients are allowed to specify the XVERP command.

TROUBLE SHOOTING CONTROLS
       The  DEBUG_README  document describes how to debug parts of the Postfix
       mail system. The methods vary from making the software  log  a  lot  of
       detail, to running some daemon processes under control of a call tracer
       or debugger.

       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
              address  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.

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

       soft_bounce (no)
              Safety  net to keep mail queued that would otherwise be returned
              to the sender.

       Available in Postfix version 2.1 and later:

       smtpd_authorized_xclient_hosts (empty)
              What SMTP clients are allowed to use the XCLIENT feature.

KNOWN VERSUS UNKNOWN RECIPIENT CONTROLS
       As of Postfix version 2.0, the SMTP server  rejects  mail  for  unknown
       recipients. This prevents the mail queue from clogging up with undeliv-
       erable MAILER-DAEMON messages. Additional information on this topic  is
       in the LOCAL_RECIPIENT_README and ADDRESS_CLASS_README documents.

       show_user_unknown_table_name (yes)
              Display  the  name  of the recipient table in the "User unknown"
              responses.

       canonical_maps (empty)
              Optional address mapping lookup tables for message  headers  and
              envelopes.

       recipient_canonical_maps (empty)
              Optional  address  mapping lookup tables for envelope and header
              recipient addresses.

       Parameters concerning known/unknown local recipients:

       mydestination ($myhostname, localhost.$mydomain, localhost)
              The list of domains that are delivered via the  $local_transport
              mail delivery transport.

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

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

       local_recipient_maps (proxy:unix:passwd.byname $alias_maps)
              Lookup tables with all names or addresses of local recipients: a
              recipient address is local when its domain  matches  $mydestina-
              tion, $inet_interfaces or $proxy_interfaces.

       unknown_local_recipient_reject_code (550)
              The numerical Postfix SMTP server response code when a recipient
              address is local, and $local_recipient_maps specifies a list  of
              lookup tables that does not match the recipient.

       Parameters concerning known/unknown recipients of relay destinations:

       relay_domains ($mydestination)
              What  destination  domains  (and subdomains thereof) this system
              will relay mail to.

       relay_recipient_maps (empty)
              Optional lookup tables with all valid addresses in  the  domains
              that match $relay_domains.

       unknown_relay_recipient_reject_code (550)
              The  numerical  Postfix  SMTP server reply code when a recipient
              address matches $relay_domains, and relay_recipient_maps  speci-
              fies  a  list of lookup tables that does not match the recipient
              address.

       Parameters  concerning  known/unknown  recipients  in   virtual   alias
       domains:

       virtual_alias_domains ($virtual_alias_maps)
              Optional  list  of  names  of  virtual  alias  domains, that is,
              domains for which all addresses  are  aliased  to  addresses  in
              other local or remote domains.

       virtual_alias_maps ($virtual_maps)
              Optional  lookup  tables  that  alias specific mail addresses or
              domains to other local or remote address.

       unknown_virtual_alias_reject_code (550)
              The SMTP server reply code  when  a  recipient  address  matches
              $virtual_alias_domains, and $virtual_alias_maps specifies a list
              of lookup tables that does not match the recipient address.

       Parameters  concerning  known/unknown  recipients  in  virtual  mailbox
       domains:

       virtual_mailbox_domains ($virtual_mailbox_maps)
              The  list  of domains that are delivered via the $virtual_trans-
              port mail delivery transport.

       virtual_mailbox_maps (empty)
              Optional lookup tables with all valid addresses in  the  domains
              that match $virtual_mailbox_domains.

       unknown_virtual_mailbox_reject_code (550)
              The  SMTP  server  reply  code  when a recipient address matches
              $virtual_mailbox_domains, and $virtual_mailbox_maps specifies  a
              list of lookup tables that does not match the recipient address.

RESOURCE AND RATE CONTROLS
       The following parameters limit resource usage by the SMTP server and/or
       control client request rates.

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

       queue_minfree (0)
              The minimal amount of free space in bytes in the queue file sys-
              tem that is needed to receive mail.

       message_size_limit (10240000)
              The maximal size in  bytes  of  a  message,  including  envelope
              information.

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

       smtpd_timeout (300s)
              The time limit for sending a Postfix SMTP  server  response  and
              for receiving a remote SMTP client request.

       smtpd_history_flush_threshold (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.

       Not available in Postfix version 2.1:

       smtpd_client_connection_count_limit (50)
              How  many simultaneous connections any SMTP client is allowed to
              make to the SMTP service.

       smtpd_client_connection_rate_limit (0)
              The maximal number of connection attempts any client is  allowed
              to make to this service per time unit.

       smtpd_client_connection_limit_exceptions ($mynetworks)
              Clients  that  are  excluded from connection count or connection
              rate restrictions.

TARPIT CONTROLS
       When a remote SMTP client makes errors, the  Postfix  SMTP  server  can
       insert  delays  before  responding. This can help to slow down run-away
       software.  The behavior is controlled by an error counter  that  counts
       the number of errors within an SMTP session that a client makes without
       delivering mail.

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

       smtpd_soft_error_limit (10)
              The  number  of  errors  a remote SMTP client is allowed to make
              without delivering mail before the  Postfix  SMTP  server  slows
              down all its responses.

       smtpd_hard_error_limit (20)
              The  maximal number of errors a remote SMTP client is allowed to
              make without delivering mail.

       smtpd_junk_command_limit (100)
              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.

       Available in Postfix version 2.1 and later:

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

ACCESS POLICY DELEGATION CONTROLS
       As  of version 2.1, Postfix can be configured to delegate access policy
       decisions to an external server that runs  outside  Postfix.   See  the
       file SMTPD_POLICY_README for more information.

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

       smtpd_policy_service_max_ttl (1000s)
              The time after which an active SMTPD policy  service  connection
              is closed.

       smtpd_policy_service_timeout (100s)
              The time limit for connecting to, writing to or receiving from a
              delegated SMTPD policy server.

ACCESS CONTROLS
       The SMTPD_ACCESS_README document gives an introduction to all the  SMTP
       server access control features.

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

       parent_domain_matches_subdomains (see 'postconf -d' output)
              What Postfix features match subdomains of "domain.tld" automati-
              cally, instead of requiring an explicit ".domain.tld" pattern.

       smtpd_client_restrictions (empty)
              Optional SMTP server access restrictions in  the  context  of  a
              client SMTP connection request.

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

       smtpd_helo_restrictions (empty)
              Optional restrictions that the Postfix SMTP  server  applies  in
              the context of the SMTP HELO command.

       smtpd_sender_restrictions (empty)
              Optional  restrictions  that  the Postfix SMTP server applies in
              the context of the MAIL FROM command.

       smtpd_recipient_restrictions (permit_mynetworks, reject_unauth_destina-
       tion)
              The  access restrictions that the Postfix SMTP server applies in
              the context of the RCPT TO command.

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

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

       smtpd_restriction_classes (empty)
              User-defined aliases for groups of access restrictions.

       smtpd_null_access_lookup_key (<&lt;>&gt;)
              The  lookup  key  to be used in SMTP access(5) tables instead of
              the null sender address.

       permit_mx_backup_networks (empty)
              Restrict the use of the permit_mx_backup SMTP access feature  to
              only domains whose primary MX hosts match the listed networks.

       Available in Postfix version 2.0 and later:

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

       smtpd_expansion_filter (see 'postconf -d' output)
              What characters are allowed in $name  expansions  of  RBL  reply
              templates.

       Available in Postfix version 2.1 and later:

       smtpd_reject_unlisted_sender (no)
              Request  that  the Postfix SMTP server rejects mail from unknown
              sender addresses, even when no  explicit  reject_unlisted_sender
              access restriction is specified.

       smtpd_reject_unlisted_recipient (yes)
              Request  that  the  Postfix SMTP server rejects mail for unknown
              recipient     addresses,     even     when      no      explicit
              reject_unlisted_recipient access restriction is specified.

SENDER AND RECIPIENT ADDRESS VERIFICATION CONTROLS
       Postfix  version  2.1 introduces sender and recipient address verifica-
       tion.  This feature is implemented by sending probe email messages that
       are  not  actually  delivered.   This  feature  is  requested  via  the
       reject_unverified_sender   and    reject_unverified_recipient    access
       restrictions.   The  status of verification probes is maintained by the
       verify(8) server.  See the file ADDRESS_VERIFICATION_README for  infor-
       mation  about how to configure and operate the Postfix sender/recipient
       address verification service.

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

       address_verify_poll_delay (3s)
              The delay between queries for the completion of an address veri-
              fication request in progress.

       address_verify_sender (postmaster)
              The sender address to use in address verification probes.

       unverified_sender_reject_code (450)
              The numerical Postfix SMTP server response code when a recipient
              address is rejected by the reject_unverified_sender restriction.

       unverified_recipient_reject_code (450)
              The  numerical  Postfix  SMTP  server  response when a recipient
              address is rejected by the reject_unverified_recipient  restric-
              tion.

ACCESS CONTROL RESPONSES
       The following parameters control numerical SMTP reply codes and/or text
       responses.

       access_map_reject_code (554)
              The numerical Postfix SMTP server response code when a client is
              rejected by an access(5) map restriction.

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

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

       maps_rbl_reject_code (554)
              The numerical Postfix SMTP server response code  when  a  remote
              SMTP   client  request  is  blocked  by  the  reject_rbl_client,
              reject_rhsbl_client, reject_rhsbl_sender or reject_rhsbl_recipi-
              ent restriction.

       non_fqdn_reject_code (504)
              The  numerical  Postfix  SMTP  server  reply  code when a client
              request   is   rejected   by    the    reject_non_fqdn_hostname,
              reject_non_fqdn_sender or reject_non_fqdn_recipient restriction.

       reject_code (554)
              The  numerical  Postfix  SMTP server response code when a remote
              SMTP client request is rejected by the "reject" restriction.

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

       unknown_address_reject_code (450)
              The numerical Postfix SMTP server response code when a sender or
              recipient       address       is       rejected      by      the
              reject_unknown_sender_domain or  reject_unknown_recipient_domain
              restriction.

       unknown_client_reject_code (450)
              The  numerical  Postfix  SMTP server response code when a client
              without valid address  <=>  name  mapping  is  rejected  by  the
              reject_unknown_client restriction.

       unknown_hostname_reject_code (450)
              The  numerical  Postfix SMTP server response code when the host-
              name specified with the HELO or EHLO command is rejected by  the
              reject_unknown_hostname restriction.

       Available in Postfix version 2.0 and later:

       default_rbl_reply (see 'postconf -d' output)
              The  default SMTP server response template for a request that is
              rejected by an RBL-based restriction.

       multi_recipient_bounce_reject_code (550)
              The numerical Postfix SMTP server response code  when  a  remote
              SMTP  client  request  is  blocked  by  the reject_multi_recipi-
              ent_bounce restriction.

       rbl_reply_maps (empty)
              Optional lookup tables with RBL response templates.

MISCELLANEOUS CONTROLS
       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
              request before it is terminated by a built-in watchdog timer.

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

       double_bounce_sender (double-bounce)
              The sender address of postmaster notifications that  are  gener-
              ated by the mail system.

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

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

       mail_owner (postfix)
              The  UNIX  system  account  that owns the Postfix queue and most
              Postfix daemon processes.

       max_idle (100s)
              The maximum amount of time that an idle Postfix  daemon  process
              waits for the next service request before exiting.

       max_use (100)
              The  maximal number of connection requests before a Postfix dae-
              mon process terminates.

       myhostname (see 'postconf -d' output)
              The internet hostname of this mail system.

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

       myorigin ($myhostname)
              The  domain  name that locally-posted mail appears to come from,
              and that locally posted mail is delivered to.

       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.

       queue_directory (see 'postconf -d' output)
              The location of the Postfix top-level queue directory.

       recipient_delimiter (empty)
              The  separator  between  user  names  and   address   extensions
              (user+foo).

       smtpd_banner ($myhostname ESMTP $mail_name)
              The  text  that follows the 220 status code in the SMTP greeting
              banner.

       syslog_facility (mail)
              The syslog facility of Postfix logging.

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

SEE ALSO
       cleanup(8), message canonicalization
       trivial-rewrite(8), address resolver
       verify(8), address verification service
       postconf(5), configuration parameters
       master(8), process manager
       syslogd(8), system logging

README FILES
       Use "postconf readme_directory" or "postconf html_directory" to  locate
       this information.
       ADDRESS_CLASS_README, blocking unknown hosted or relay recipients
       FILTER_README, external after-queue content filter
       LOCAL_RECIPIENT_README, blocking unknown local recipients
       SMTPD_ACCESS_README, built-in access policies
       SMTPD_POLICY_README, external policy server
       SMTPD_PROXY_README, external before-queue content filter
       SASL_README, Postfix SASL howto
       VERP_README, Postfix XVERP extension
       XCLIENT_README, Postfix XCLIENT extension
       XFORWARD_README, Postfix XFORWARD extension

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



                                                                      SMTPD(8)