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    Command:

    smtp

    
    
    

    SYNOPSIS

           smtp [generic Postfix daemon options]
    
    
    

    DESCRIPTION

           The Postfix SMTP+LMTP client implements the SMTP and LMTP mail delivery
           protocols. It processes message delivery requests from the  queue  man-
           ager.  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+LMTP  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+LMTP 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+LMTP 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+LMTP 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. Connection caching
           can be enabled permanently for specific destinations.
    
    
    

    SMTP DESTINATION SYNTAX

           SMTP destinations have the following form:
    
           domainname
    
           domainname:port
                  Look up the mail exchangers for the specified domain,  and  con-
                  nect to the specified port (default: smtp).
    
           [hostname]
    
           [hostname]:port
                  Look  up  the  address(es) of the specified host, and connect to
                  the specified port (default: smtp).
    
           [address]
    
           [address]:port
                  Connect to the host at the specified address, and connect to the
                  specified  port (default: smtp). An IPv6 address must be format-
                  ted as [ipv6:address].
    
           inet:[address]:port
                  Connect  to  the  specified  TCP  port on the specified local or
                  remote host. If no  port  is  specified,  connect  to  the  port
                  defined  as  lmtp  in services(4).  If no such service is found,
                  the lmtp_tcp_port configuration parameter (default value of  24)
                  will   be   used.    An   IPv6  address  must  be  formatted  as
                  [ipv6:address].
    
    
    

    SECURITY

           The SMTP+LMTP client is moderately security-sensitive. It talks to SMTP
           or LMTP servers and to DNS servers on the network. The SMTP+LMTP 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 2033 (LMTP protocol)
           RFC 2034 (SMTP Enhanced Error Codes)
           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)
           RFC 3461 (SMTP DSN Extension)
           RFC 3463 (Enhanced Status Codes)
           RFC 4954 (AUTH 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  postmas-
           ter is notified of bounces, protocol problems, and of other trouble.
    
    
    

    BUGS

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

    CONFIGURATION PARAMETERS

           Before  Postfix version 2.3, the LMTP client is a separate program that
    
    
    

    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_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 Postfix SMTP client
                  turns on the PIX firewall "<CR><LF>.<CR><LF>" bug workaround for
                  delivery through firewalls with "smtp fixup" mode turned on.
    
           smtp_pix_workarounds (disable_esmtp, delay_dotcrlf)
                  A  list  that  specifies  zero or more workarounds for CISCO PIX
                  firewall bugs.
    
           smtp_pix_workaround_maps (empty)
                  Lookup tables, indexed by the remote SMTP server  address,  with
                  per-destination workarounds for CISCO PIX firewall bugs.
    
           smtp_quote_rfc821_envelope (yes)
                  Quote  addresses  in  SMTP  MAIL  FROM  and  RCPT TO commands as
                  required by RFC 2821.
    
           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).
    
           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.
    
           Available in Postfix version 2.2.9 and later:
    
           smtp_cname_overrides_servername (version dependent)
                  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.
    
           Available in Postfix version 2.3 and later:
    
           lmtp_discard_lhlo_keyword_address_maps (empty)
                  Lookup tables, indexed by the remote LMTP server  address,  with
                  case  insensitive  lists of LHLO keywords (pipelining, starttls,
                  auth, etc.) that  the  LMTP  client  will  ignore  in  the  LHLO
                  response from a remote LMTP server.
    
           lmtp_discard_lhlo_keywords (empty)
                  A  case insensitive list of LHLO keywords (pipelining, starttls,
                  auth, etc.) that  the  LMTP  client  will  ignore  in  the  LHLO
                  response from a remote LMTP server.
    
           Available in Postfix version 2.4.4 and later:
    
           send_cyrus_sasl_authzid (no)
                  When  authenticating  to  a  remote SMTP or LMTP server with the
                  default setting "no", send no SASL authoriZation  ID  (authzid);
                  send  only  the  SASL authentiCation ID (authcid) plus the auth-
                  cid's password.
    
           Available in Postfix version 2.5 and later:
    
           smtp_header_checks (empty)
                  Restricted header_checks(5) tables for the Postfix SMTP  client.
    
           smtp_mime_header_checks (empty)
                  Restricted  mime_header_checks(5)  tables  for  the Postfix SMTP
                  client.
    
           smtp_nested_header_checks (empty)
                  Restricted nested_header_checks(5) tables for the  Postfix  SMTP
                  client.
    
           smtp_body_checks (empty)
                  Restricted body_checks(5) tables for the Postfix SMTP client.
    
           Available in Postfix version 2.6 and later:
    
           tcp_windowsize (0)
    
    
    

    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, or sender address when
                  sender-dependent authentication is enabled.
    
           smtp_sasl_security_options (noplaintext, noanonymous)
                  Postfix SMTP client SASL security options; as of Postfix 2.3 the
                  list  of available features depends on the SASL client implemen-
                  tation that is selected with smtp_sasl_type.
    
           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.
    
           Available in Postfix version 2.3 and later:
    
           smtp_sender_dependent_authentication (no)
                  Enable  sender-dependent  authentication  in  the  Postfix  SMTP
                  client; this is available only  with  SASL  authentication,  and
                  disables  SMTP  connection caching to ensure that mail from dif-
                  ferent senders will use the appropriate credentials.
    
           smtp_sasl_path (empty)
                  Implementation-specific information that the Postfix SMTP client
                  passes  through  to  the  SASL  plug-in  implementation  that is
                  selected with smtp_sasl_type.
    
           smtp_sasl_type (cyrus)
                  The SASL plug-in type that the Postfix SMTP  client  should  use
                  for authentication.
    
           Available in Postfix version 2.5 and later:
    
           smtp_sasl_auth_cache_name (empty)
                  An  optional table to prevent repeated SASL authentication fail-
                  ures with the same remote SMTP  server  hostname,  username  and
                  password.
    
                  The default SMTP TLS security level for the Postfix SMTP client;
                  when a non-empty value is specified, this overrides the obsolete
                  parameters       smtp_use_tls,       smtp_enforce_tls,       and
                  smtp_tls_enforce_peername.
    
           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)
                  A file containing CA certificates of root CAs  trusted  to  sign
                  either  remote  SMTP server certificates or intermediate CA cer-
                  tificates.
    
           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_mandatory_ciphers (medium)
                  The  minimum  TLS cipher grade that the Postfix SMTP client will
                  use with mandatory TLS encryption.
    
           smtp_tls_exclude_ciphers (empty)
                  List of ciphers or cipher types to exclude from the Postfix SMTP
                  client cipher list at all TLS security levels.
    
           smtp_tls_mandatory_exclude_ciphers (empty)
                  Additional  list  of ciphers or cipher types to exclude from the
                  SMTP client cipher list at mandatory TLS security levels.
    
           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_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,
    
           smtp_tls_secure_cert_match (nexthop, dot-nexthop)
                  The  server  certificate  peername  verification  method for the
                  "secure" TLS security level.
    
           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.
    
           smtp_tls_verify_cert_match (hostname)
                  The server certificate  peername  verification  method  for  the
                  "verify" TLS security level.
    
           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).
    
           tls_high_cipherlist (ALL:!EXPORT:!LOW:!MEDIUM:+RC4:@STRENGTH)
                  The OpenSSL cipherlist for "HIGH" grade ciphers.
    
           tls_medium_cipherlist (ALL:!EXPORT:!LOW:+RC4:@STRENGTH)
                  The OpenSSL cipherlist for "MEDIUM" or higher grade ciphers.
    
           tls_low_cipherlist (ALL:!EXPORT:+RC4:@STRENGTH)
                  The OpenSSL cipherlist for "LOW" or higher grade ciphers.
    
           tls_export_cipherlist (ALL:+RC4:@STRENGTH)
                  The OpenSSL cipherlist for "EXPORT" or higher grade ciphers.
    
           tls_null_cipherlist (eNULL:!aNULL)
                  The  OpenSSL  cipherlist  for  "NULL" grade ciphers that provide
                  authentication without encryption.
    
           Available in Postfix version 2.4 and later:
    
           smtp_sasl_tls_verified_security_options           ($smtp_sasl_tls_secu-
           rity_options)
                  The SASL authentication security options that the  Postfix  SMTP
                  client  uses  for  TLS  encrypted  SMTP sessions with a verified
                  server certificate.
    
           Available in Postfix version 2.5 and later:
    
           smtp_tls_fingerprint_cert_match (empty)
                  List of acceptable remote SMTP server  certificate  fingerprints
                  for   the   "fingerprint"  TLS  security  level  (smtp_tls_secu-
                  rity_level = fingerprint).
    
           smtp_tls_eccert_file (empty)
                  File  with the Postfix SMTP client ECDSA certificate in PEM for-
                  mat.
    
           smtp_tls_eckey_file ($smtp_tls_eccert_file)
                  File with the Postfix SMTP client ECDSA private key in PEM  for-
                  mat.
    
    
    

    OBSOLETE STARTTLS CONTROLS

           The  following  configuration  parameters  exist for compatibility with
           Postfix versions before 2.3. Support for these will  be  removed  in  a
           future release.
    
           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_tls_enforce_peername (yes)
                  With  mandatory  TLS  encryption,  require  that the remote SMTP
                  server hostname matches  the  information  in  the  remote  SMTP
                  server certificate.
    
           smtp_tls_per_site (empty)
                  Optional  lookup  tables  with the Postfix SMTP client TLS usage
                  policy by next-hop destination and by remote SMTP  server  host-
                  name.
    
           smtp_tls_cipherlist (empty)
                  Obsolete  Postfix  < 2.3 control for the Postfix SMTP client TLS
                  cipher list.
    
    
    

    RESOURCE AND RATE CONTROLS

           smtp_destination_concurrency_limit        ($default_destination_concur-
           rency_limit)
                  The maximal number of parallel deliveries to the  same  destina-
                  tion via the smtp message delivery transport.
    
           smtp_destination_recipient_limit ($default_destination_recipient_limit)
                  The  maximal  number of recipients per message for the smtp mes-
                  sage 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.
                  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 (5)
                  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 earlier:
    
           lmtp_cache_connection (yes)
                  Keep Postfix LMTP client connections open for  up  to  $max_idle
                  seconds.
    
           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_reuse_time_limit (300s)
                  The amount of time during which Postfix will use an SMTP connec-
                  tion repeatedly.
                  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 proto-
                  col errors.
    
           internal_mail_filter_classes (empty)
                  What categories of Postfix-generated mail are subject to before-
                  queue content inspection by non_smtpd_milters, header_checks and
                  body_checks.
    
           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 'postconf -d' output)
                  The default location of the Postfix main.cf and  master.cf  con-
                  figuration 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.
    
           delay_logging_resolution_limit (2)
                  The maximal number of digits after the decimal point  when  log-
                  ging sub-second delay values.
    
           disable_dns_lookups (no)
                  Disable DNS lookups in the Postfix SMTP and LMTP clients.
    
           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.
    
                  process will service before terminating voluntarily.
    
           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  Postfix  SMTP
                  client should bind to when making an IPv4 connection.
    
           smtp_bind_address6 (empty)
                  An  optional  numerical  network  address  that the Postfix 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.
    
           lmtp_lhlo_name ($myhostname)
                  The hostname to send in the LMTP LHLO command.
    
           smtp_host_lookup (dns)
                  What mechanisms when the Postfix 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 (see 'postconf -d' output)
                  The  mail  system  name that is prepended to the process name in
                  syslog records, so that "smtpd"  becomes,  for  example,  "post-
                  fix/smtpd".
    
           Available with Postfix 2.2 and earlier:
    
           fallback_relay (empty)
                  Optional list of relay hosts for SMTP destinations that can't be
                  found or that are unreachable.
    
           Available with Postfix 2.3 and later:
    
           smtp_fallback_relay ($fallback_relay)
                  Optional list of relay hosts for SMTP destinations that can't be
                  found or that are unreachable.
    
    
    

    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.
    
           SASL support originally by:
           Till Franke
           SuSE Rhein/Main AG
           65760 Eschborn, Germany
    
           TLS support originally by:
           Lutz Jaenicke
           BTU Cottbus
           Allgemeine Elektrotechnik
           Universitaetsplatz 3-4
           D-03044 Cottbus, Germany
    
           Revised TLS and SMTP connection cache support by:
           Victor Duchovni
           Morgan Stanley
    
                                                                           SMTP(8)
    
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