Provided by: postfix_2.2.10-1_i386 bug

NAME

       smtp - Postfix SMTP client

SYNOPSIS

       smtp [generic Postfix daemon options]

DESCRIPTION

       The  Postfix  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 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
       finished, or it informs the queue manager that delivery should be tried
       again at a  later  time.  Delivery  status  reports  are  sent  to  the
       bounce(8), defer(8) or trace(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.

       When  a  server  is not reachable, or when mail delivery fails due to a
       recoverable error condition, the SMTP client will try  to  deliver  the
       mail to an alternate host.

       After  a  successful mail transaction, a connection may be saved to the
       scache(8) connection cache server, so that it may be used by  any  SMTP
       client for a subsequent transaction.

       By  default, connection caching is enabled temporarily for destinations
       that have a high volume of mail in the active  queue.  Session  caching
       can be enabled permanently for specific destinations.

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)
       RFC 3207 (STARTTLS command)

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
       postmaster is notified of bounces,  protocol  problems,  and  of  other
       trouble.

BUGS

       SMTP  connection  caching does not work with TLS. The necessary support
       for TLS object passivation and re-activation  does  not  exist  without
       closing the session, which defeats the purpose.

       SMTP connection caching assumes that SASL credentials are valid for all
       destinations that map onto the same IP address and TCP port.

CONFIGURATION PARAMETERS

       Changes to main.cf are picked up automatically,  as  smtp(8)  processes
       run for only a limited amount of time. Use the command "postfix reload"
       to speed up a change.

       The text below provides only a parameter summary. See  postconf(5)  for
       more details including examples.

COMPATIBILITY CONTROLS

       ignore_mx_lookup_error (no)
              Ignore DNS MX lookups that produce no response.

       smtp_always_send_ehlo (yes)
              Always send EHLO at the start of an SMTP session.

       smtp_never_send_ehlo (no)
              Never send EHLO at the start of an SMTP session.

       smtp_cname_overrides_servername (yes)
              Allow  DNS  CNAME  records  to  override the servername that the
              Postfix SMTP client uses for logging, SASL password lookup,  TLS
              policy decisions, or TLS certificate verification.

       smtp_defer_if_no_mx_address_found (no)
              Defer mail delivery when no MX record resolves to an IP address.

       smtp_line_length_limit (990)
              The maximal length of message header and body lines that Postfix
              will send via SMTP.

       smtp_pix_workaround_delay_time (10s)
              How   long   the  Postfix  SMTP  client  pauses  before  sending
              ".<CR><LF>"  in  order  to  work   around   the   PIX   firewall
              "<CR><LF>.<CR><LF>" bug.

       smtp_pix_workaround_threshold_time (500s)
              How  long  a  message  must  be  queued  before the PIX firewall
              "<CR><LF>.<CR><LF>" bug workaround is turned on.

       smtp_quote_rfc821_envelope (yes)
              Quote addresses in SMTP  MAIL  FROM  and  RCPT  TO  commands  as
              required by RFC 821.

       smtp_skip_5xx_greeting (yes)
              Skip SMTP servers that greet with a 5XX status code (go away, do
              not try again later).

       smtp_skip_quit_response (yes)
              Do not wait for the response to the SMTP QUIT command.

       Available in Postfix version 2.0 and earlier:

       smtp_skip_4xx_greeting (yes)
              Skip SMTP servers that greet with a 4XX status  code  (go  away,
              try again later).

       Available in Postfix version 2.2 and later:

       smtp_discard_ehlo_keyword_address_maps (empty)
              Lookup  tables,  indexed by the remote SMTP server address, with
              case insensitive lists of EHLO keywords  (pipelining,  starttls,
              auth,  etc.)  that  the  SMTP  client  will  ignore  in the EHLO
              response from a remote SMTP server.

       smtp_discard_ehlo_keywords (empty)
              A case insensitive list of EHLO keywords (pipelining,  starttls,
              auth,  etc.)  that  the  SMTP  client  will  ignore  in the EHLO
              response from a remote SMTP server.

       smtp_generic_maps (empty)
              Optional lookup tables that perform  address  rewriting  in  the
              SMTP client, typically to transform a locally valid address into
              a globally valid address when sending mail across the  Internet.

MIME PROCESSING CONTROLS

       Available in Postfix version 2.0 and later:

       disable_mime_output_conversion (no)
              Disable the conversion of 8BITMIME format to 7BIT format.

       mime_boundary_length_limit (2048)
              The maximal length of MIME multipart boundary strings.

       mime_nesting_limit (100)
              The maximal recursion level that the MIME processor will handle.

EXTERNAL CONTENT INSPECTION CONTROLS

       Available in Postfix version 2.1 and later:

       smtp_send_xforward_command (no)
              Send the non-standard XFORWARD command  when  the  Postfix  SMTP
              server EHLO response announces XFORWARD support.

SASL AUTHENTICATION CONTROLS

       smtp_sasl_auth_enable (no)
              Enable SASL authentication in the Postfix SMTP client.

       smtp_sasl_password_maps (empty)
              Optional  SMTP  client  lookup tables with one username:password
              entry per remote hostname or domain.

       smtp_sasl_security_options (noplaintext, noanonymous)
              What  authentication  mechanisms  the  Postfix  SMTP  client  is
              allowed to use.

       Available in Postfix version 2.2 and later:

       smtp_sasl_mechanism_filter (empty)
              If  non-empty,  a Postfix SMTP client filter for the remote SMTP
              server’s list of offered SASL mechanisms.

STARTTLS SUPPORT CONTROLS

       Detailed information about STARTTLS configuration may be found  in  the
       TLS_README document.

       smtp_use_tls (no)
              Opportunistic  mode: use TLS when a remote SMTP server announces
              STARTTLS support, otherwise send the mail in the clear.

       smtp_enforce_tls (no)
              Enforcement mode: require  that  remote  SMTP  servers  use  TLS
              encryption, and never send mail in the clear.

       smtp_sasl_tls_security_options ($smtp_sasl_security_options)
              The  SASL  authentication security options that the Postfix SMTP
              client uses for TLS encrypted SMTP sessions.

       smtp_starttls_timeout (300s)
              Time limit for Postfix SMTP client  write  and  read  operations
              during TLS startup and shutdown handshake procedures.

       smtp_tls_CAfile (empty)
              The  file  with  the  certificate of the certification authority
              (CA) that issued the Postfix SMTP client certificate.

       smtp_tls_CApath (empty)
              Directory with PEM  format  certificate  authority  certificates
              that the Postfix SMTP client uses to verify a remote SMTP server
              certificate.

       smtp_tls_cert_file (empty)
              File with the Postfix SMTP client RSA certificate in PEM format.

       smtp_tls_cipherlist (empty)
              Controls the Postfix SMTP client TLS cipher selection scheme.

       smtp_tls_dcert_file (empty)
              File with the Postfix SMTP client DSA certificate in PEM format.

       smtp_tls_dkey_file ($smtp_tls_dcert_file)
              File with the Postfix SMTP client DSA private key in PEM format.

       smtp_tls_enforce_peername (yes)
              When  TLS  encryption  is enforced, require that the remote SMTP
              server hostname matches  the  information  in  the  remote  SMTP
              server certificate.

       smtp_tls_key_file ($smtp_tls_cert_file)
              File with the Postfix SMTP client RSA private key in PEM format.

       smtp_tls_loglevel (0)
              Enable additional Postfix SMTP client logging of TLS activity.

       smtp_tls_note_starttls_offer (no)
              Log the hostname of a remote SMTP server that  offers  STARTTLS,
              when TLS is not already enabled for that server.

       smtp_tls_per_site (empty)
              Optional  lookup  tables  with the Postfix SMTP client TLS usage
              policy by  next-hop  domain  name  and  by  remote  SMTP  server
              hostname.

       smtp_tls_scert_verifydepth (5)
              The verification depth for remote SMTP server certificates.

       smtp_tls_session_cache_database (empty)
              Name of the file containing the optional Postfix SMTP client TLS
              session cache.

       smtp_tls_session_cache_timeout (3600s)
              The expiration time of Postfix SMTP  client  TLS  session  cache
              information.

       tls_daemon_random_bytes (32)
              The  number  of  pseudo-random bytes that an smtp(8) or smtpd(8)
              process requests from the tlsmgr(8) server in order to seed  its
              internal pseudo random number generator (PRNG).

RESOURCE AND RATE CONTROLS

       smtp_destination_concurrency_limit
       ($default_destination_concurrency_limit)
              The   maximal   number   of  parallel  deliveries  to  the  same
              destination via the smtp message delivery transport.

       smtp_destination_recipient_limit ($default_destination_recipient_limit)
              The maximal number of  recipients  per  delivery  via  the  smtp
              message delivery transport.

       smtp_connect_timeout (30s)
              The  SMTP  client time limit for completing a TCP connection, or
              zero (use the operating system built-in time limit).

       smtp_helo_timeout (300s)
              The SMTP client time limit for sending the HELO or EHLO command,
              and for receiving the initial server response.

       smtp_xforward_timeout (300s)
              The SMTP client time limit for sending the XFORWARD command, and
              for receiving the server response.

       smtp_mail_timeout (300s)
              The SMTP client time limit for sending the  MAIL  FROM  command,
              and for receiving the server response.

       smtp_rcpt_timeout (300s)
              The SMTP client time limit for sending the SMTP RCPT TO command,
              and for receiving the server response.

       smtp_data_init_timeout (120s)
              The SMTP client time limit for sending the  SMTP  DATA  command,
              and for receiving the server response.

       smtp_data_xfer_timeout (180s)
              The SMTP client time limit for sending the SMTP message content.

       smtp_data_done_timeout (600s)
              The SMTP client time limit for sending the  SMTP  ".",  and  for
              receiving the server response.

       smtp_quit_timeout (300s)
              The SMTP client time limit for sending the QUIT command, and for
              receiving the server response.

       Available in Postfix version 2.1 and later:

       smtp_mx_address_limit (0)
              The maximal number of MX (mail exchanger) IP addresses that  can
              result from mail exchanger lookups, or zero (no limit).

       smtp_mx_session_limit (2)
              The  maximal number of SMTP sessions per delivery request before
              giving up or delivering to a fall-back relay host, or  zero  (no
              limit).

       smtp_rset_timeout (20s)
              The SMTP client time limit for sending the RSET command, and for
              receiving the server response.

       Available in Postfix version 2.2 and later:

       smtp_connection_cache_destinations (empty)
              Permanently enable SMTP connection  caching  for  the  specified
              destinations.

       smtp_connection_cache_on_demand (yes)
              Temporarily  enable  SMTP connection caching while a destination
              has a high volume of mail in the active queue.

       smtp_connection_cache_reuse_limit (10)
              When SMTP connection caching is enabled,  the  number  of  times
              that an SMTP session is reused before it is closed.

       smtp_connection_cache_time_limit (2s)
              When SMTP connection caching is enabled, the amount of time that
              an unused SMTP client socket is kept open before it is closed.

TROUBLE SHOOTING CONTROLS

       debug_peer_level (2)
              The increment in verbose logging level when a remote  client  or
              server matches a pattern in the debug_peer_list parameter.

       debug_peer_list (empty)
              Optional  list  of  remote  client or server hostname or network
              address  patterns  that  cause  the  verbose  logging  level  to
              increase by the amount specified in $debug_peer_level.

       error_notice_recipient (postmaster)
              The  recipient  of  postmaster notifications about mail delivery
              problems that  are  caused  by  policy,  resource,  software  or
              protocol errors.

       notify_classes (resource, software)
              The list of error classes that are reported to the postmaster.

MISCELLANEOUS CONTROLS

       best_mx_transport (empty)
              Where  the  Postfix  SMTP  client  should  deliver  mail when it
              detects a "mail loops back to myself" error condition.

       config_directory (see â€â€™postconf -dâ€â€™ output)
              The default  location  of  the  Postfix  main.cf  and  master.cf
              configuration files.

       daemon_timeout (18000s)
              How  much  time  a  Postfix  daemon process may take to handle a
              request before it is terminated by a built-in watchdog timer.

       disable_dns_lookups (no)
              Disable DNS lookups in the Postfix SMTP and LMTP clients.

       fallback_relay (empty)
              Optional list of relay hosts for SMTP destinations that can’t be
              found or that are unreachable.

       inet_interfaces (all)
              The  network  interface addresses that this mail system receives
              mail on.

       inet_protocols (ipv4)
              The Internet protocols Postfix will attempt to use  when  making
              or accepting connections.

       ipc_timeout (3600s)
              The  time  limit  for  sending  or receiving information over an
              internal communication channel.

       max_idle (100s)
              The maximum amount of time that an idle Postfix  daemon  process
              waits for the next service request before exiting.

       max_use (100)
              The  maximal  number  of  connection  requests  before a Postfix
              daemon process terminates.

       process_id (read-only)
              The process ID of a Postfix command or daemon process.

       process_name (read-only)
              The process name of a Postfix command or daemon process.

       proxy_interfaces (empty)
              The network interface addresses that this mail  system  receives
              mail on by way of a proxy or network address translation unit.

       smtp_bind_address (empty)
              An  optional  numerical  network  address  that  the SMTP client
              should bind to when making an IPv4 connection.

       smtp_bind_address6 (empty)
              An optional numerical  network  address  that  the  SMTP  client
              should bind to when making an IPv6 connection.

       smtp_helo_name ($myhostname)
              The hostname to send in the SMTP EHLO or HELO command.

       smtp_host_lookup (dns)
              What mechanisms when the SMTP client uses to look up a host’s IP
              address.

       smtp_randomize_addresses (yes)
              Randomize the order of equal-preference MX host addresses.

       syslog_facility (mail)
              The syslog facility of Postfix logging.

       syslog_name (postfix)
              The mail system name that is prepended to the  process  name  in
              syslog   records,   so   that   "smtpd"  becomes,  for  example,
              "postfix/smtpd".

SEE ALSO

       qmgr(8), queue manager
       bounce(8), delivery status reports
       scache(8), connection cache server
       postconf(5), configuration parameters
       master(5), generic daemon options
       master(8), process manager
       tlsmgr(8), TLS session and PRNG management
       syslogd(8), system logging

README FILES

       Use "postconf readme_directory" or "postconf html_directory" to  locate
       this information.
       SASL_README, Postfix SASL howto
       TLS_README, Postfix STARTTLS howto

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

       Command pipelining in cooperation with:
       Jon Ribbens
       Oaktree Internet Solutions Ltd.,
       Internet House,
       Canal Basin,
       Coventry,
       CV1 4LY, United Kingdom.

       Connection caching in cooperation with:
       Victor Duchovni
       Morgan Stanley

       TLS support originally by:
       Lutz Jaenicke
       BTU Cottbus
       Allgemeine Elektrotechnik
       Universitaetsplatz 3-4
       D-03044 Cottbus, Germany

                                                                       SMTP(8)