Postfix manual - smtpd(8)

    SMTPD(8)                                                              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) dae-
           mon, and is placed into the incoming queue as  one  single
           queue  file.   For  this  mode  of  operation, the program
           expects to be run from the master(8) process manager.

           Alternatively, the SMTP server takes an  established  con-
           nection  on  standard 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  con-
           nection  requests, and for parameters given to HELO, ETRN,
           MAIL FROM, VRFY and RCPT TO commands.  They  are  detailed
           below and in the main.cf configuration 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)
           RFC 3207 (STARTTLS command)

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

           Depending  on the setting of the notify_classes parameter,
           the postmaster 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  com-
                  ments 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  sup-
                  port 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  key-
                  words  (pipelining,  starttls, auth, etc.) that the
                  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 (pipelin-
                  ing, starttls, auth, etc.)  that  the  SMTP  server
                  will not send in the EHLO response to a remote SMTP
                  client.

    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 filtering, 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_rewrite_domain 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 further 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 config-
           ured to send incoming mail to a real-time SMTP-based  con-
           tent filter BEFORE mail is queued.  This content filter is
           expected to  inject  mail  back  into  Postfix.   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 filter.

           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 filtering, 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 SMTP clients are allowed to use  the  XFORWARD
                  feature.

    SASL AUTHENTICATION CONTROLS
           Postfix  SASL  support (RFC 2554) can be used to authenti-
           cate 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 initial-
                  ization.

           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  sup-
                  port to.

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

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

           smtpd_enforce_tls (no)
                  Enforcement mode: announce STARTTLS support to SMTP
                  clients,  and  require that clients use TLS encryp-
                  tion.

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

           smtpd_starttls_timeout (300s)
                  The time limit for Postfix SMTP  server  write  and
                  read  operations  during  TLS  startup and shutdown
                  handshake procedures.

           smtpd_tls_CAfile (empty)
                  The file with the certificate of the  certification
                  authority  (CA) that issued the Postfix SMTP server
                  certificate.

           smtpd_tls_CAfile (empty)
                  The file with the certificate of the  certification
                  authority  (CA) that issued the Postfix SMTP server
                  certificate.

           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  authentica-
                  tion over unencrypted connections.

           smtpd_tls_ccert_verifydepth (5)
                  The  verification depth for remote SMTP client cer-
                  tificates.

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

           smtpd_tls_cipherlist (empty)
                  Controls  the Postfix SMTP server TLS cipher selec-
                  tion scheme.

           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 EDH ciphers.

           smtpd_tls_dh512_param_file (empty)
                  File with  DH  parameters  that  the  Postfix  SMTP
                  server should use with 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_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
                  client  CommonName  and  client  certificate issuer
                  CommonName.

           smtpd_tls_req_ccert (no)
                  When TLS encryption is enforced, require  a  remote
                  SMTP  client certificate in order to allow TLS con-
                  nections to proceed.

           smtpd_tls_session_cache_database (empty)
                  Name of the file containing  the  optional  Postfix
                  SMTP server TLS session cache.

           smtpd_tls_session_cache_timeout (3600s)
                  The expiration time of Postfix SMTP server TLS ses-
                  sion cache information.

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

           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).

    VERP SUPPORT CONTROLS
           With  VERP  style  delivery,  each  recipient of a message
           receives a customized copy of the message with his/her own
           recipient  address encoded in the envelope sender address.
           The VERP_README file describes configuration 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 pro-
           cesses 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 protocol 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  undeliverable  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,  local-
           host)
                  The list of domains  that  are  delivered  via  the
                  $local_transport mail delivery transport.

           inet_interfaces (all)
                  The network interface addresses that this mail sys-
                  tem receives mail on.

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

           inet_protocols (ipv4)
                  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 $mydestination, $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 specifies  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 SMTP server reply code when a recipient address
                  matches    $virtual_alias_domains,    and     $vir-
                  tual_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)
                  Postfix is final destination for the specified list
                  of  domains;  mail  is  delivered  via  the   $vir-
                  tual_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 SMTP server reply code when a recipient address
                  matches    $virtual_mailbox_domains,    and   $vir-
                  tual_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 system 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.

           The per SMTP client connection count and request rate lim-
           its are implemented in co-operation with the anvil(8) ser-
           vice,  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 connection count,
                  connection rate, or SMTP request 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 con-
           trolled 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_restric-
                  tions and $smtpd_sender_restrictions, or wait until
                  the     ETRN     command     before      evaluating
                  $smtpd_client_restrictions and $smtpd_helo_restric-
                  tions.

           parent_domain_matches_subdomains (see 'postconf  -d'  out-
           put)
                  What   Postfix   features   match   subdomains   of
                  "domain.tld" automatically, 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_destination)
                  The  access  restrictions  that  the  Postfix  SMTP
                  server applies in the context of the RCPT  TO  com-
                  mand.

           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 destinations matching $relay_domains.

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

           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 com-
                  mand.

           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  restric-
                  tion 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.

    SENDER AND RECIPIENT ADDRESS VERIFICATION CONTROLS
           Postfix   version  2.1  introduces  sender  and  recipient
           address verification.   This  feature  is  implemented  by
           sending  probe email messages that are not actually deliv-
           ered.  This feature is requested  via  the  reject_unveri-
           fied_sender    and    reject_unverified_recipient   access
           restrictions.  The status of verification probes is  main-
           tained by the verify(8) server.  See the file ADDRESS_VER-
           IFICATION_README for information about  how  to  configure
           and operate the Postfix sender/recipient address verifica-
           tion 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 verification 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_unveri-
                  fied_recipient restriction.

    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 restric-
                  tion.

           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_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_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 map-
                  ping  is  rejected  by  the   reject_unknown_client
                  restriction.

           unknown_hostname_reject_code (450)
                  The  numerical  Postfix  SMTP  server response code
                  when the hostname 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 restric-
                  tion.

           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_recipient_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 configuration 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  com-
                  mands.

           double_bounce_sender (double-bounce)
                  The sender address of postmaster notifications that
                  are generated 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 daemon 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 deliv-
                  ered 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  direc-
                  tory.

           recipient_delimiter (empty)
                  The separator between user names and address exten-
                  sions (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, "postfix/smtpd".

           Available in Postfix version 2.2 and later:

           smtpd_forbidden_commands (CONNECT, GET, POST)
                  List  of  commands  that  causes  the  Postfix SMTP
                  server to immediately terminate the session with  a
                  221 code.

    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
           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

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

                                                                          SMTPD(8)