Postfix manual - smtpd(8)

    SMTPD(8)                                                              SMTPD(8)

    NAME
           smtpd - Postfix SMTP server

    SYNOPSIS
           smtpd [generic Postfix daemon options]

           sendmail -bs

    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 be can run in stand-alone mode; this is
           traditionally obtained with "sendmail -bs".  When the SMTP server  runs
           stand-alone  with  non  $mail_owner  privileges,  it receives mail even
           while the mail system is not running, deposits messages  directly  into
           the  maildrop queue, and disables the SMTP server's access policies. As
           of Postfix version 2.3, the SMTP server refuses to  receive  mail  from
           the network when it runs with non $mail_owner privileges.

           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 2034 (SMTP enhanced status codes)
           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 3848 (ESMTP transmission types)
           RFC 4409 (Message submission)
           RFC 4954 (AUTH command)
           RFC 5321 (SMTP protocol)

    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 remote SMTP clients that implement
                  an obsolete version of the AUTH command (RFC 4954).

           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:

           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 remote SMTP clients the Postfix SMTP server will not  offer
                  AUTH support to.

           Available in Postfix version 2.2 and later:

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

           smtpd_discard_ehlo_keywords (empty)
                  A case insensitive list of EHLO keywords (pipelining,  starttls,
                  auth,  etc.)  that  the Postfix SMTP server will not send in the
                  EHLO response to a remote SMTP client.

           smtpd_delay_open_until_valid_rcpt (yes)
                  Postpone the start of an SMTP mail  transaction  until  a  valid
                  RCPT TO command is received.

           Available in Postfix version 2.3 and later:

           smtpd_tls_always_issue_session_ids (yes)
                  Force  the  Postfix  SMTP server to issue a TLS session id, even
                  when  TLS  session  caching  is   turned   off   (smtpd_tls_ses-
                  sion_cache_database is empty).

           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 2.7 and later:

           smtpd_command_filter (empty)
                  A mechanism to transform commands from remote SMTP clients.

           Available in Postfix version 2.9 and later:

           smtpd_per_record_deadline (normal: no, overload: yes)
                  Change  the  behavior  of  the  smtpd_timeout  and  smtpd_start-
                  tls_timeout  time  limits,  from  a time limit per read or write
                  system call, to a time limit  to  send  or  receive  a  complete
                  record  (an  SMTP command line, SMTP response line, SMTP message
                  content line, or TLS protocol message).

    ADDRESS REWRITING CONTROLS
           See the ADDRESS_REWRITING_README document for a detailed discussion  of
           Postfix address rewriting.

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

           Available in Postfix version 2.2 and later:

           local_header_rewrite_clients (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 rewrite message headers and update incomplete
                  addresses with the domain  specified  in  the  remote_header_re-
                  write_domain parameter.

    BEFORE-SMTPD PROXY AGENT
           Available in Postfix version 2.10 and later:

           smtpd_upstream_proxy_protocol (empty)
                  The  name of the proxy protocol used by an optional before-smtpd
                  proxy agent.

           smtpd_upstream_proxy_timeout (5s)
                  The time  limit  for  the  proxy  protocol  specified  with  the
                  smtpd_upstream_proxy_protocol parameter.

    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)
                  After the message is queued, send  the  entire  message  to  the
                  specified transport:destination.

    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_options (empty)
                  List of options that control how the Postfix SMTP server  commu-
                  nicates with a before-queue content filter.

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

    BEFORE QUEUE MILTER CONTROLS
           As of version 2.3, Postfix supports the Sendmail version 8 Milter (mail
           filter)  protocol.  These content filters run outside Postfix. They can
           inspect the SMTP command  stream  and  the  message  content,  and  can
           request  modifications  before mail is queued. For details see the MIL-
           TER_README document.

           smtpd_milters (empty)
                  A list of Milter (mail filter) applications for  new  mail  that
                  arrives via the Postfix smtpd(8) server.

           milter_protocol (6)
                  The  mail  filter  protocol version and optional protocol exten-
                  sions for communication with  a  Milter  application;  prior  to
                  Postfix 2.6 the default protocol is 2.

           milter_default_action (tempfail)
                  The  default  action  when a Milter (mail filter) application is
                  unavailable or mis-configured.

           milter_macro_daemon_name ($myhostname)
                  The {daemon_name} macro value for Milter (mail filter)  applica-
                  tions.

           milter_macro_v ($mail_name $mail_version)
                  The {v} macro value for Milter (mail filter) applications.

           milter_connect_timeout (30s)
                  The time limit for connecting to a Milter (mail filter) applica-
                  tion, and for negotiating protocol options.

           milter_command_timeout (30s)
                  The time limit for sending an SMTP command  to  a  Milter  (mail
                  filter) application, and for receiving the response.

           milter_content_timeout (300s)
                  The  time  limit  for  sending message content to a Milter (mail
                  filter) application, and for receiving the response.

           milter_connect_macros (see 'postconf -d' output)
                  The macros that are sent to Milter  (mail  filter)  applications
                  after completion of an SMTP connection.

           milter_helo_macros (see 'postconf -d' output)
                  The  macros  that  are sent to Milter (mail filter) applications
                  after the SMTP HELO or EHLO command.

           milter_mail_macros (see 'postconf -d' output)
                  The macros that are sent to Milter  (mail  filter)  applications
                  after the SMTP MAIL FROM command.

           milter_rcpt_macros (see 'postconf -d' output)
                  The  macros  that  are sent to Milter (mail filter) applications
                  after the SMTP RCPT TO command.

           milter_data_macros (see 'postconf -d' output)
                  The macros that are sent to version 4  or  higher  Milter  (mail
                  filter) applications after the SMTP DATA command.

           milter_unknown_command_macros (see 'postconf -d' output)
                  The  macros  that  are  sent to version 3 or higher Milter (mail
                  filter) applications after an unknown SMTP command.

           milter_end_of_header_macros (see 'postconf -d' output)
                  The macros that are sent to Milter  (mail  filter)  applications
                  after the end of the message header.

           milter_end_of_data_macros (see 'postconf -d' output)
                  The  macros  that  are sent to Milter (mail filter) applications
                  after the message end-of-data.

    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 mapping.

    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  remote  SMTP  clients are allowed to use the XFORWARD fea-
                  ture.

    SASL AUTHENTICATION CONTROLS
           Postfix SASL support (RFC 4954) 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 remote SMTP clients that implement
                  an obsolete version of the AUTH command (RFC 4954).

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

           smtpd_sasl_local_domain (empty)
                  The name of the Postfix SMTP server's local SASL  authentication
                  realm.

           smtpd_sasl_security_options (noanonymous)
                  Postfix SMTP server SASL security options; as of Postfix 2.3 the
                  list of available features depends on the SASL server  implemen-
                  tation that is selected with smtpd_sasl_type.

           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 remote SMTP clients the Postfix SMTP server will not  offer
                  AUTH support to.

           Available in Postfix version 2.1 and 2.2:

           smtpd_sasl_application_name (smtpd)
                  The  application name that the Postfix SMTP server uses for SASL
                  server initialization.

           Available in Postfix version 2.3 and later:

           smtpd_sasl_authenticated_header (no)
                  Report the SASL authenticated user name in the smtpd(8) Received
                  message header.

           smtpd_sasl_path (smtpd)
                  Implementation-specific information that the Postfix SMTP server
                  passes through  to  the  SASL  plug-in  implementation  that  is
                  selected with smtpd_sasl_type.

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

           Available in Postfix version 2.5 and later:

           cyrus_sasl_config_path (empty)
                  Search path for Cyrus SASL application configuration files, cur-
                  rently used only to locate the $smtpd_sasl_path.conf file.

           Available in Postfix version 2.11 and later:

           smtpd_sasl_service (smtp)
                  The  service  name  that  is  passed to the SASL plug-in that is
                  selected with smtpd_sasl_type and smtpd_sasl_path.

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

           smtpd_tls_security_level (empty)
                  The  SMTP TLS security level for the Postfix SMTP server; when a
                  non-empty value is specified, this overrides the obsolete param-
                  eters smtpd_use_tls and smtpd_enforce_tls.

           smtpd_sasl_tls_security_options ($smtpd_sasl_security_options)
                  The  SASL  authentication security options that the Postfix SMTP
                  server uses for TLS encrypted SMTP sessions.

           smtpd_starttls_timeout (see 'postconf -d' output)
                  The time limit for Postfix SMTP server write and read operations
                  during TLS startup and shutdown handshake procedures.

           smtpd_tls_CAfile (empty)
                  A  file  containing  (PEM  format)  CA  certificates of root CAs
                  trusted to sign either remote SMTP client certificates or inter-
                  mediate CA certificates.

           smtpd_tls_CApath (empty)
                  A  directory containing (PEM format) CA certificates of root CAs
                  trusted to sign either remote SMTP client certificates or inter-
                  mediate CA certificates.

           smtpd_tls_always_issue_session_ids (yes)
                  Force  the  Postfix  SMTP server to issue a TLS session id, even
                  when  TLS  session  caching  is   turned   off   (smtpd_tls_ses-
                  sion_cache_database is empty).

           smtpd_tls_ask_ccert (no)
                  Ask a remote SMTP client for a client certificate.

           smtpd_tls_auth_only (no)
                  When  TLS  encryption is optional in the Postfix SMTP server, do
                  not announce or accept SASL authentication over unencrypted con-
                  nections.

           smtpd_tls_ccert_verifydepth (9)
                  The verification depth for remote SMTP client certificates.

           smtpd_tls_cert_file (empty)
                  File with the Postfix SMTP server RSA certificate in PEM format.

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

           smtpd_tls_dcert_file (empty)
                  File with the Postfix SMTP server DSA certificate in PEM format.

           smtpd_tls_dh1024_param_file (empty)
                  File with DH parameters that the Postfix SMTP server should  use
                  with non-export EDH ciphers.

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

           smtpd_tls_dkey_file ($smtpd_tls_dcert_file)
                  File with the Postfix SMTP server DSA private key in PEM format.

           smtpd_tls_key_file ($smtpd_tls_cert_file)
                  File with the Postfix SMTP server RSA private key in PEM format.

           smtpd_tls_loglevel (0)
                  Enable additional Postfix SMTP server logging of TLS activity.

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

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

           smtpd_tls_mandatory_protocols (!SSLv2, !SSLv3)
                  The  SSL/TLS  protocols accepted by the Postfix SMTP server with
                  mandatory TLS encryption.

           smtpd_tls_received_header (no)
                  Request that the Postfix SMTP server produces Received:  message
                  headers  that  include information about the protocol and cipher
                  used, as well as the remote SMTP client  CommonName  and  client
                  certificate issuer CommonName.

           smtpd_tls_req_ccert (no)
                  With  mandatory  TLS  encryption,  require a trusted remote SMTP
                  client certificate in order to allow TLS connections to proceed.

           smtpd_tls_wrappermode (no)
                  Run  the Postfix SMTP server in the non-standard "wrapper" mode,
                  instead of using the STARTTLS command.

           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
                  authentication without encryption.

           Available in Postfix version 2.5 and later:

           smtpd_tls_fingerprint_digest (md5)
                  The  message  digest  algorithm to construct remote SMTP client-
                  certificate fingerprints or public key fingerprints (Postfix 2.9
                  and later) for check_ccert_access and permit_tls_clientcerts.

           Available in Postfix version 2.6 and later:

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

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

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

           smtpd_tls_eckey_file ($smtpd_tls_eccert_file)
                  File with the Postfix SMTP server ECDSA private key in PEM  for-
                  mat.

           smtpd_tls_eecdh_grade (see 'postconf -d' output)
                  The  Postfix  SMTP server security grade for ephemeral elliptic-
                  curve Diffie-Hellman (EECDH) key exchange.

           tls_eecdh_strong_curve (prime256v1)
                  The elliptic curve used by the Postfix SMTP server for  sensibly
                  strong ephemeral ECDH key exchange.

           tls_eecdh_ultra_curve (secp384r1)
                  The elliptic curve used by the Postfix SMTP server for maximally
                  strong ephemeral ECDH key exchange.

           Available in Postfix version 2.8 and later:

           tls_preempt_cipherlist (no)
                  With SSLv3 and later, use the Postfix SMTP server's cipher pref-
                  erence  order  instead  of the remote client's cipher preference
                  order.

           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:

           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
           future release.

           smtpd_use_tls (no)
                  Opportunistic TLS: announce  STARTTLS  support  to  remote  SMTP
                  clients, but do not require that clients use TLS encryption.

           smtpd_enforce_tls (no)
                  Mandatory TLS: announce STARTTLS support to remote SMTP clients,
                  and require that clients use TLS encryption.

           smtpd_tls_cipherlist (empty)
                  Obsolete Postfix < 2.3 control for the Postfix SMTP  server  TLS
                  cipher list.

    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 remote SMTP clients are allowed to specify the  XVERP  com-
                  mand.

           Available in Postfix version 2.1 and later:

           smtpd_authorized_verp_clients ($authorized_verp_clients)
                  What  remote  SMTP clients are allowed to specify the XVERP com-
                  mand.

    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.

           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.

           smtpd_reject_footer (empty)
                  Optional information that is appended after  each  Postfix  SMTP
                  server 4XX or 5XX response.

           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 remote SMTP clients are allowed to use the XCLIENT feature.

           Available in Postfix version 2.10 and later:

           smtpd_log_access_permit_actions (empty)
                  Enable  logging  of  the  named  "permit" actions in SMTP server
                  access lists (by default, the SMTP server logs "reject"  actions
                  but not "permit" actions).

    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.

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

           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)
                  Postfix  is  final destination for the specified list of virtual
                  alias domains, that is, domains  for  which  all  addresses  are
                  aliased to addresses in other local or remote domains.

           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 Postfix SMTP server reply  code  when  a  recipient  address
                  matches  $virtual_alias_domains,  and $virtual_alias_maps speci-
                  fies 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)
                  Postfix is final destination for the specified list of  domains;
                  mail  is  delivered  via  the  $virtual_transport  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  Postfix  SMTP  server  reply  code when a recipient address
                  matches  $virtual_mailbox_domains,   and   $virtual_mailbox_maps
                  specifies a list of lookup tables that does not match the recip-
                  ient 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 (normal: 300s, overload: 10s)
                  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.

           Available in Postfix version 2.3 and later:

           smtpd_peername_lookup (yes)
                  Attempt to look up the remote SMTP client hostname,  and  verify
                  that the name matches the client IP address.

           The per SMTP client connection count and request rate limits are imple-
           mented in co-operation with the anvil(8) service, and are available  in
           Postfix version 2.2 and later.

           smtpd_client_connection_count_limit (50)
                  How  many simultaneous connections any client is allowed to make
                  to this 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_message_rate_limit (0)
                  The  maximal number of message delivery requests that any client
                  is allowed to make to this service per time unit, regardless  of
                  whether or not Postfix actually accepts those messages.

           smtpd_client_recipient_rate_limit (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 Postfix actually accepts those recipients.

           smtpd_client_event_limit_exceptions ($mynetworks)
                  Clients  that  are excluded from smtpd_client_*_count/rate_limit
                  restrictions.

           Available in Postfix version 2.3 and later:

           smtpd_client_new_tls_session_rate_limit (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.

           Available in Postfix version 2.9 and later:

           smtpd_per_record_deadline (normal: no, overload: yes)
                  Change  the  behavior  of  the  smtpd_timeout  and  smtpd_start-
                  tls_timeout  time  limits,  from  a time limit per read or write
                  system call, to a time limit  to  send  or  receive  a  complete
                  record  (an  SMTP command line, SMTP response line, SMTP message
                  content line, or TLS protocol message).

    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 version 2.1 and later:  the  SMTP  server  response
                  delay  after a client has made more than $smtpd_soft_error_limit
                  errors, and fewer than $smtpd_hard_error_limit  errors,  without
                  delivering mail.

           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 (normal: 20, overload: 1)
                  The  maximal number of errors a remote SMTP client is allowed to
                  make without delivering mail.

           smtpd_junk_command_limit (normal: 100, overload: 1)
                  The number of junk commands (NOOP, VRFY, ETRN or  RSET)  that  a
                  remote  SMTP  client  can  send  before  the Postfix SMTP server
                  starts to increment the error counter with each junk command.

           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 restrictions that the Postfix SMTP  server  applies  in
                  the context of a client connection request.

           smtpd_helo_required (no)
                  Require  that  a  remote  SMTP client introduces itself with the
                  HELO or EHLO command before sending the MAIL  command  or  other
                  commands that require EHLO negotiation.

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

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

           smtpd_recipient_restrictions (see 'postconf -d' output)
                  Optional  restrictions  that  the Postfix SMTP server applies in
                  the   context   of   a   client   RCPT   TO    command,    after
                  smtpd_relay_restrictions.

           smtpd_etrn_restrictions (empty)
                  Optional  restrictions  that  the Postfix SMTP server applies in
                  the context of a client ETRN command.

           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 (<>)
                  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.

           Available in Postfix version 2.2 and later:

           smtpd_end_of_data_restrictions (empty)
                  Optional  access  restrictions  that  the  Postfix  SMTP  server
                  applies in the context of the SMTP END-OF-DATA command.

           Available in Postfix version 2.10 and later:

           smtpd_relay_restrictions (permit_mynetworks, permit_sasl_authenticated,
           defer_unauth_destination)
                  Access restrictions for mail relay control that the Postfix SMTP
                  server applies in the context of the  RCPT  TO  command,  before
                  smtpd_recipient_restrictions.

    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 (normal: 3, overload: 1)
                  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 ($double_bounce_sender)
                  The sender address to use in address verification probes;  prior
                  to Postfix 2.5 the default was "postmaster".

           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.

           Available in Postfix version 2.6 and later:

           unverified_sender_defer_code (450)
                  The  numerical  Postfix  SMTP server response code when a sender
                  address probe fails due to a temporary error condition.

           unverified_recipient_defer_code (450)
                  The numerical Postfix SMTP  server  response  when  a  recipient
                  address probe fails due to a temporary error condition.

           unverified_sender_reject_reason (empty)
                  The  Postfix  SMTP  server's  reply  when  rejecting  mail  with
                  reject_unverified_sender.

           unverified_recipient_reject_reason (empty)
                  The  Postfix  SMTP  server's  reply  when  rejecting  mail  with
                  reject_unverified_recipient.

           unverified_sender_tempfail_action ($reject_tempfail_action)
                  The  Postfix  SMTP server's action when reject_unverified_sender
                  fails due to a temporary error condition.

           unverified_recipient_tempfail_action ($reject_tempfail_action)
                  The Postfix SMTP server's action when  reject_unverified_recipi-
                  ent fails due to a temporary error condition.

           Available with Postfix 2.9 and later:

           address_verify_sender_ttl (0s)
                  The  time  between  changes  in  the  time-dependent  portion of
                  address verification probe sender addresses.

    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 for an access(5)
                  map "reject" action.

           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_helo_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_reverse_client,
                  reject_rhsbl_sender or reject_rhsbl_recipient restriction.

           non_fqdn_reject_code (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.

           plaintext_reject_code (450)
                  The  numerical  Postfix SMTP server response code when a request
                  is rejected by the reject_plaintext_session 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_hostname 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_helo_hostname restriction.

           Available in Postfix version 2.0 and later:

           default_rbl_reply (see 'postconf -d' output)
                  The default Postfix 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.

           Available in Postfix version 2.6 and later:

           access_map_defer_code (450)
                  The numerical Postfix SMTP server response code for an access(5)
                  map   "defer"    action,    including    "defer_if_permit"    or
                  "defer_if_reject".

           reject_tempfail_action (defer_if_permit)
                  The  Postfix SMTP server's action when a reject-type restriction
                  fails due to a temporary error condition.

           unknown_helo_hostname_tempfail_action ($reject_tempfail_action)
                  The Postfix SMTP server's action when  reject_unknown_helo_host-
                  name fails due to an temporary error condition.

           unknown_address_tempfail_action ($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 condition.

    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 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.

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

           mynetworks (see 'postconf -d' output)
                  The list of "trusted" remote SMTP clients that have more  privi-
                  leges 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 set of characters that can separate a  user  name  from  its
                  extension  (example: user+foo), or a .forward file name from its
                  extension (example: .forward+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 (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 in Postfix version 2.2 and later:

           smtpd_forbidden_commands (CONNECT, GET, POST)
                  List  of  commands that cause the Postfix SMTP server to immedi-
                  ately terminate the session with a 221 code.

           Available in Postfix version 2.5 and later:

           smtpd_client_port_logging (no)
                  Enable logging of the remote SMTP client port in addition to the
                  hostname and IP address.

    SEE ALSO
           anvil(8), connection/rate limiting
           cleanup(8), message canonicalization
           tlsmgr(8), TLS session and PRNG management
           trivial-rewrite(8), address resolver
           verify(8), address verification service
           postconf(5), configuration parameters
           master(5), generic daemon options
           master(8), process manager
           syslogd(8), system logging

    README FILES
           ADDRESS_CLASS_README, blocking unknown hosted or relay recipients
           ADDRESS_REWRITING_README Postfix address manipulation
           FILTER_README, external after-queue content filter
           LOCAL_RECIPIENT_README, blocking unknown local recipients
           MILTER_README, before-queue mail filter applications
           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
           TLS_README, Postfix STARTTLS 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

           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 support by:
           Victor Duchovni
           Morgan Stanley

                                                                          SMTPD(8)