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<html> <head> </head> <body> <pre>



SMTP(8)                                                   SMTP(8)


<b>NAME</b>
       smtp - Postfix remote delivery via SMTP

<b>SYNOPSIS</b>
       <b>smtp</b> [generic Postfix daemon options]

<b>DESCRIPTION</b>
       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
       <a href="master.8.html"><b>master</b>(8)</a> 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 <a href="bounce.8.html"><b>bounce</b>(8)</a> or <a href="defer.8.html"><b>defer</b>(8)</a> 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.

<b>SECURITY</b>
       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.

<b>STANDARDS</b>
       RFC 821 (SMTP protocol)
       RFC 1651 (SMTP service extensions)
       RFC 1870 (Message Size Declaration)
       RFC 2197 (Pipelining)

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

       Depending on the setting of the <b>notify</b><i>_</i><b>classes</b>  parameter,
       the  postmaster is notified of bounces, protocol problems,
       and of other trouble.

<b>BUGS</b>
<b>CONFIGURATION</b> <b>PARAMETERS</b>
       The following <b>main.cf</b> parameters are  especially  relevant
       to  this  program. See the Postfix <b>main.cf</b> file for syntax
       details and for default values.  Use  the  <b>postfix</b>  <b>reload</b>



                                                                1





SMTP(8)                                                   SMTP(8)


       command after a configuration change.

<b>Miscellaneous</b>
       <b>best</b><i>_</i><b>mx</b><i>_</i><b>transport</b>
              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).

       <b>debug</b><i>_</i><b>peer</b><i>_</i><b>level</b>
              Verbose logging  level  increment  for  hosts  that
              match a pattern in the <b>debug</b><i>_</i><b>peer</b><i>_</i><b>list</b> parameter.

       <b>debug</b><i>_</i><b>peer</b><i>_</i><b>list</b>
              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
              <b>debug</b><i>_</i><b>peer</b><i>_</i><b>level</b> parameter.

       <b>disable</b><i>_</i><b>dns</b><i>_</i><b>lookups</b>
              Disable DNS lookups. This means that mail  must  be
              forwarded via a smart relay host.

       <b>error</b><i>_</i><b>notice</b><i>_</i><b>recipient</b>
              Recipient    of   protocol/policy/resource/software
              error notices.

       <b>fallback</b><i>_</i><b>relay</b>
              Hosts to hand off mail to if a message  destination
              is not found or if a destination is unreachable.

       <b>ignore</b><i>_</i><b>mx</b><i>_</i><b>lookup</b><i>_</i><b>error</b>
              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.

       <b>inet</b><i>_</i><b>interfaces</b>
              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.

       <b>notify</b><i>_</i><b>classes</b>
              When  this  parameter  includes the <b>protocol</b> class,
              send mail to the  postmaster  with  transcripts  of
              SMTP sessions with protocol errors.

       <b>smtp</b><i>_</i><b>skip</b><i>_</i><b>4xx</b><i>_</i><b>greeting</b>
              Skip  servers that greet us with a 4xx status code.

       <b>smtp</b><i>_</i><b>skip</b><i>_</i><b>quit</b><i>_</i><b>response</b>
              Do not wait for the server response  after  sending
              QUIT.



                                                                2





SMTP(8)                                                   SMTP(8)


<b>Resource</b> <b>controls</b>
       <b>smtp</b><i>_</i><b>destination</b><i>_</i><b>concurrency</b><i>_</i><b>limit</b>
              Limit the number of parallel deliveries to the same
              destination.  The default limit is taken  from  the
              <b>default</b><i>_</i><b>destination</b><i>_</i><b>concurrency</b><i>_</i><b>limit</b> parameter.

       <b>smtp</b><i>_</i><b>destination</b><i>_</i><b>recipient</b><i>_</i><b>limit</b>
              Limit  the  number of recipients per message deliv-
              ery.   The  default  limit  is   taken   from   the
              <b>default</b><i>_</i><b>destination</b><i>_</i><b>recipient</b><i>_</i><b>limit</b> parameter.

<b>Timeout</b> <b>controls</b>
       <b>smtp</b><i>_</i><b>connect</b><i>_</i><b>timeout</b>
              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.

       <b>smtp</b><i>_</i><b>helo</b><i>_</i><b>timeout</b>
              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.

       <b>smtp</b><i>_</i><b>helo</b><i>_</i><b>timeout</b>
              Timeout  in  seconds  for sending the <b>HELO</b> command,
              and for receiving the server response.

       <b>smtp</b><i>_</i><b>mail</b><i>_</i><b>timeout</b>
              Timeout in seconds for sending the <b>MAIL</b>  <b>FROM</b>  com-
              mand, and for receiving the server response.

       <b>smtp</b><i>_</i><b>rcpt</b><i>_</i><b>timeout</b>
              Timeout in seconds for sending the <b>RCPT</b> <b>TO</b> command,
              and for receiving the server response.

       <b>smtp</b><i>_</i><b>data</b><i>_</i><b>init</b><i>_</i><b>timeout</b>
              Timeout in seconds for sending  the  <b>DATA</b>  command,
              and for receiving the server response.

       <b>smtp</b><i>_</i><b>data</b><i>_</i><b>xfer</b><i>_</i><b>timeout</b>
              Timeout in seconds for sending the message content.

       <b>smtp</b><i>_</i><b>data</b><i>_</i><b>done</b><i>_</i><b>timeout</b>
              Timeout in seconds for sending the "<b>.</b>" command, and
              for receiving the server response. When no response
              is received, a warning is logged that the mail  may
              be delivered multiple times.

       <b>smtp</b><i>_</i><b>quit</b><i>_</i><b>timeout</b>
              Timeout  in  seconds  for sending the <b>QUIT</b> command,
              and for receiving the server response.



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SMTP(8)                                                   SMTP(8)


<b>SEE</b> <b>ALSO</b>
       <a href="bounce.8.html">bounce(8)</a> non-delivery status reports
       <a href="master.8.html">master(8)</a> process manager
       <a href="qmgr.8.html">qmgr(8)</a> queue manager
       syslogd(8) system logging

<b>LICENSE</b>
       The Secure Mailer license must be  distributed  with  this
       software.

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










































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