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SMTP(8)                     System Manager's Manual                    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 man-
       ager. Each request specifies a queue file, a sender address,  a  domain
       or host to deliver to, and recipient information.  This program expects
       to be run from the master(8) process manager.

       The SMTP client updates the queue file and  marks  recipients  as  fin-
       ished,  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).  Corrupted message
       files are marked so that the queue manager can move them to the corrupt
       queue for further inspection.

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

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 commands 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 command.

       Available in Postfix version 2.0 and earlier:

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

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  pro-
              cessor will handle.

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

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

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

       smtp_sasl_password_maps (empty)
              Optional SMTP client lookup tables  with  one  username: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_destination_concur-
       rency_limit)
              The  maximal  number of parallel deliveries to the same destina-
              tion via the smtp message delivery transport.

       smtp_destination_recipient_limit ($default_destination_recipient_limit)
              The maximal number of recipients per delivery via the smtp  mes-
              sage 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 proto-
              col 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 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.

       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  system  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 dae-
              mon process terminates.

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

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

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

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

       smtp_bind_address6 (empty)
              An optional numerical IPv6 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 command.

       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  process  name  in
              syslog  records,  so  that  "smtpd" becomes, for example, "post-
              fix/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
       Use "postconf readme_directory" or "postconf html_directory" to  locate
       this information.
       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)