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 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).  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
       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  deferring  mail
              delivery.
       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.   See  also  the  proxy_interfaces
              parameter.
       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 trans-
              lator. 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 connection.
       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_bound-
              ary_length_limit characters.
       mime_nesting_limit
              The maximal nesting level of  multipart  mail  that
              the  MIME processor can handle. Refuse mail that is
              nested deeper, when converting 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 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
       The  default  time  unit is seconds; an explicit time unit
       can be specified 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  send-
              ing 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)