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.

       When the domain or host is specified as a comma/whitespace
       separated  list, the SMTP client repeats the above process
       for  all  destinations  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.



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SMTP(8)                                                   SMTP(8)


BUGS
CONFIGURATION PARAMETERS
       The  following  main.cf parameters are especially relevant
       to this program. 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 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.





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SMTP(8)                                                   SMTP(8)


       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.

       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



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SMTP(8)                                                   SMTP(8)


              delivery.   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.
              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





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SMTP(8)                                                   SMTP(8)


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
















































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