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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  problem  reports  are  sent  to  the
       bounce(8) or defer(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.

       Once  the SMTP client has received the server greeting banner, no error
       will cause it to proceed to the next  address  on  the  mail  exchanger
       list.  Instead,  the  message  is  either  bounced,  or its delivery is
       deferred until later.

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.

BUGS
CONFIGURATION PARAMETERS
       The  following  main.cf parameters are especially relevant to this pro-
       gram. See the Postfix main.cf file for syntax details and  for  default
       values. Use the postfix reload command after a configuration change.

Miscellaneous
       best_mx_transport
              Name  of the delivery transport to use when the local machine is
              the most-preferred mail exchanger (by default, a mailer loop  is
              reported, and the message is bounced).

       debug_peer_level
              Verbose  logging  level increment for hosts that match a pattern
              in the debug_peer_list parameter.

       debug_peer_list
              List of domain or network patterns. When a remote host matches a
              pattern, increase the verbose logging level by the amount speci-
              fied in the debug_peer_level parameter.

       disable_dns_lookups
              Disable DNS lookups. This means that mail must be forwarded  via
              a smart relay host.

       error_notice_recipient
              Recipient of protocol/policy/resource/software error notices.

       fallback_relay
              Hosts  to hand off mail to if a message destination is not found
              or if a destination is unreachable.

       ignore_mx_lookup_error
              When a name server fails to respond to an MX query,  search  for
              an A record instead deferring mail delivery.

       inet_interfaces
              The  network  interface addresses that this mail system receives
              mail on. When any of those addresses appears in the list of mail
              exchangers  for  a  remote destination, the list is truncated to
              avoid mail delivery loops.  See also the proxy_interfaces param-
              eter.

       notify_classes
              When  this  parameter  includes the protocol class, send mail to
              the postmaster with transcripts of SMTP sessions  with  protocol
              errors.

       proxy_interfaces
              Network interfaces that this mail system receives mail on by way
              of a proxy or network address  translator.  When  any  of  those
              addresses  appears  in  the list of mail exchangers for a remote
              destination, the list is truncated to avoid mail delivery loops.
              See also the inet_interfaces parameter.

       smtp_always_send_ehlo
              Always send EHLO at the start of a connection.

       smtp_never_send_ehlo
              Never send EHLO at the start of a connection.

       smtp_bind_address
              Numerical  source  network address to bind to when making a con-
              nection.

       smtp_line_length_limit
              Length limit for SMTP  message  content  lines.  Zero  means  no
              limit.  Some SMTP servers misbehave on long lines.

       smtp_helo_name
              The hostname to be used in HELO and EHLO commands.

       smtp_skip_4xx_greeting
              Skip servers that greet us with a 4xx status code.

       smtp_skip_5xx_greeting
              Skip servers that greet us with a 5xx status code.

       smtp_skip_quit_response
              Do not wait for the server response after sending QUIT.

       smtp_pix_workaround_delay_time
              The time to pause before sending .<CR><LF>, while working around
              the CISCO PIX firewall <CR><LF>.<CR><LF> bug.

       smtp_pix_workaround_threshold_time
              The time a message must be queued before the CISCO PIX  firewall
              <CR><LF>.<CR><LF> bug workaround is turned on.

MIME Conversion
       disable_mime_output_conversion
              Disable  the  conversion  of 8BITMIME format to 7BIT format when
              the remote system does not advertise 8BITMIME support.

       mime_boundary_length_limit
              The amount of space that will be allocated  for  MIME  multipart
              boundary  strings.  The  MIME processor is unable to distinguish
              between boundary  strings  that  do  not  differ  in  the  first
              $mime_boundary_length_limit characters.

       mime_nesting_limit
              The  maximal  nesting level of multipart mail that the MIME pro-
              cessor can handle. Refuse mail that is nested deeper, when  con-
              verting from 8BITMIME format to 7BIT format.

Authentication controls
       smtp_sasl_auth_enable
              Enable  per-session  authentication  as per RFC 2554 (SASL).  By
              default, Postfix is built without SASL support.

       smtp_sasl_password_maps
              Lookup tables with per-host or domain name:password entries.  No
              entry for a host means no attempt to authenticate.

       smtp_sasl_security_options
              Zero or more of the following.

              noplaintext
                     Disallow  authentication methods that use plaintext pass-
                     words.

              noactive
                     Disallow authentication methods that  are  vulnerable  to
                     non-dictionary active attacks.

              nodictionary
                     Disallow  authentication  methods  that are vulnerable to
                     passive dictionary attack.

              noanonymous
                     Disallow anonymous logins.

Resource controls
       smtp_destination_concurrency_limit
              Limit the number of parallel deliveries to the same destination.
              The  default limit is taken from the default_destination_concur-
              rency_limit parameter.

       smtp_destination_recipient_limit
              Limit the  number  of  recipients  per  message  delivery.   The
              default  limit  is  taken  from  the default_destination_recipi-
              ent_limit parameter.

Timeout controls
       The default time unit is seconds; an explicit time unit can  be  speci-
       fied  by  appending  a  one-letter  suffix to the value: s (seconds), m
       (minutes), h (hours), d (days) or w (weeks).

       smtp_connect_timeout
              Timeout for completing a TCP connection. When no connection  can
              be  made  within  the  deadline,  the SMTP client tries the next
              address on the mail exchanger list.

       smtp_helo_timeout
              Timeout for receiving the SMTP greeting banner.  When the server
              drops  the connection without sending a greeting banner, or when
              it sends no greeting banner within the deadline, the SMTP client
              tries the next address on the mail exchanger list.

       smtp_helo_timeout
              Timeout  for  sending  the  HELO  command, and for receiving the
              server response.

       smtp_mail_timeout
              Timeout for sending the MAIL FROM command, and for receiving the
              server response.

       smtp_rcpt_timeout
              Timeout  for  sending the RCPT TO command, and for receiving the
              server response.

       smtp_data_init_timeout
              Timeout for sending the DATA  command,  and  for  receiving  the
              server response.

       smtp_data_xfer_timeout
              Timeout for sending the message content.

       smtp_data_done_timeout
              Timeout  for  sending  the  "."  command,  and for receiving the
              server response. When no response  is  received,  a  warning  is
              logged that the mail may be delivered multiple times.

       smtp_quit_timeout
              Timeout  for  sending  the  QUIT  command, and for receiving the
              server response.

SEE ALSO
       bounce(8) non-delivery status reports
       master(8) process manager
       qmgr(8) queue manager
       syslogd(8) system logging

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)