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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
       problem reports are sent to the bounce(8) or defer(8) dae-
       mon 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 ban-
       ner, 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 1651 (SMTP service extensions)
       RFC 1870 (Message Size Declaration)
       RFC 2197 (Pipelining)
       RFC 2554 (AUTH command)

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.

BUGS
CONFIGURATION PARAMETERS
       The following main.cf parameters are  especially  relevant
       to  this  program. See the Postfix main.cf file for syntax



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SMTP(8)                                                   SMTP(8)


       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  log-
              ging   level   by   the  amount  specified  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 of assuming that the
              name server will recover.

       inet_interfaces
              The network interface addresses that this mail sys-
              tem 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.

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

       smtp_always_send_ehlo
              Always send EHLO at the start of a connection.

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



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SMTP(8)                                                   SMTP(8)


       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_bind_address
              Numerical network address to bind to when making  a
              connection.

Authentication controls
       smtp_enable_sasl_auth
              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 passwords.

              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_concurrency_limit parameter.

       smtp_destination_recipient_limit
              Limit  the  number of recipients per message deliv-
              ery.   The  default  limit  is   taken   from   the
              default_destination_recipient_limit parameter.

Timeout controls
       smtp_connect_timeout
              Timeout in seconds for completing a TCP connection.



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SMTP(8)                                                   SMTP(8)


              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 in seconds for receiving the SMTP  greeting
              banner.  When the server drops the connection with-
              out 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  in  seconds  for sending the HELO command,
              and for receiving the server response.

       smtp_mail_timeout
              Timeout in seconds for sending the MAIL  FROM  com-
              mand, and for receiving the server response.

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

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

       smtp_data_xfer_timeout
              Timeout in seconds for sending the message content.

       smtp_data_done_timeout
              Timeout in seconds 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  in  seconds  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



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SMTP(8)                                                   SMTP(8)


       P.O. Box 704
       Yorktown Heights, NY 10598, USA























































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