Postfix manual - smtp(8)

    SMTP(8)                                                   SMTP(8)

    NAME
           smtp - Postfix remote delivery via SMTP

    SYNOPSIS
           smtp [generic Postfix daemon options]

    DESCRIPTION
           The  SMTP  client processes message delivery requests from
           the queue manager. Each request specifies a queue file,  a
           sender address, a domain or host to deliver to, and recip-
           ient information.  This program expects to be run from the
           master(8) process manager.

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

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

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

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

    STANDARDS
           RFC 821 (SMTP protocol)
           RFC 822 (ARPA Internet Text Messages)
           RFC 1651 (SMTP service extensions)
           RFC 1652 (8bit-MIME transport)
           RFC 1870 (Message Size Declaration)
           RFC 2045 (MIME: Format of Internet Message Bodies)
           RFC 2046 (MIME: Media Types)
           RFC 2554 (AUTH command)
           RFC 2821 (SMTP protocol)
           RFC 2920 (SMTP Pipelining)

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

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

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

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

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

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

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

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

           smtp_line_length_limit (990)
                  The maximal length of message header and body lines
                  that Postfix will send via SMTP.

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

           smtp_pix_workaround_threshold_time (500s)
                  How  long  a  message must be queued before the PIX
                  firewall  "<CR><LF>.<CR><LF>"  bug  workaround   is
                  turned on.

           smtp_quote_rfc821_envelope (yes)
                  Quote  addresses in SMTP MAIL FROM and RCPT TO com-
                  mands as required by RFC 821.

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

           smtp_skip_quit_response (yes)
                  Do  not wait for the response to the SMTP QUIT com-
                  mand.

           Available in Postfix version 2.0 and earlier:

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

    MIME PROCESSING CONTROLS
           Available in Postfix version 2.0 and later:

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

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

           mime_nesting_limit (100)
                  The  maximal  nesting  level of multipart mail that
                  the MIME processor will handle.

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

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

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

           smtp_sasl_password_maps (empty)
                  Optional  SMTP  client lookup tables with one user-
                  name:password entry per remote hostname or  domain.

           smtp_sasl_security_options (noplaintext, noanonymous)
                  What  authentication  mechanisms  the  Postfix SMTP
                  client is allowed to use.

    RESOURCE AND RATE CONTROLS
           smtp_destination_concurrency_limit      ($default_destina-
           tion_concurrency_limit)
                  The maximal number of parallel  deliveries  to  the
                  same  destination  via  the  smtp  message delivery
                  transport.

           smtp_destination_recipient_limit        ($default_destina-
           tion_recipient_limit)
                  The maximal number of recipients per  delivery  via
                  the smtp message delivery transport.

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

           smtp_helo_timeout (300s)
                  The  SMTP client time limit for sending the HELO or
                  EHLO command, and for receiving the initial  server
                  response.

           smtp_xforward_timeout (300s)
                  The SMTP client time limit for sending the XFORWARD
                  command, and for receiving the server response.

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

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

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

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

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

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

           Available in Postfix version 2.1 and later:

           smtp_mx_address_limit (0)
                  The  maximal  number  of  MX  (mail  exchanger)  IP
                  addresses  that  can  result  from  mail  exchanger
                  lookups, or zero (no limit).

           smtp_mx_session_limit (2)
                  The  maximal  number  of SMTP sessions per delivery
                  request before giving up or delivering to  a  fall-
                  back relay host, or zero (no limit).

           smtp_rset_timeout (120s)
                  The  SMTP  client  time  limit for sending the RSET
                  command, and for receiving the server response.

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

           debug_peer_list (empty)
                  Optional list of remote client or  server  hostname
                  or  network 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.

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

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

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

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

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

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

           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.

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

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

           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.

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

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

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

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

           syslog_facility (mail)
                  The syslog facility of Postfix logging.

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

    SEE ALSO
           qmgr(8), queue manager
           bounce(8), delivery status reports
           postconf(5), configuration parameters
           master(8), process manager
           syslogd(8), system logging

    README FILES
           SASL_README, Postfix SASL howto

    LICENSE
           The  Secure  Mailer  license must be distributed with this
           software.

    AUTHOR(S)
           Wietse Venema
           IBM T.J. Watson Research
           P.O. Box 704
           Yorktown Heights, NY 10598, USA

                                                              SMTP(8)