Postfix manual - smtp(8)

    SMTP(8)                                                                SMTP(8)

    NAME
           smtp - Postfix SMTP+LMTP client

    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 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+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 connect 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 formatted as [ipv6:address].

    LMTP DESTINATION SYNTAX
           LMTP destinations have the following form:

           unix:pathname
                  Connect  to  the  local  UNIX-domain server that is
                  bound to the specified  pathname.  If  the  process
                  runs  chrooted, an absolute pathname is interpreted
                  relative to the Postfix queue directory.

           inet:hostname

           inet:hostname:port

           inet:[address]

           inet:[address]:port
                  Connect to the specified TCP port on the  specified
                  local or remote host. If no port is specified, con-
                  nect to the port defined as  lmtp  in  services(4).
                  If no such service is found, the lmtp_tcp_port con-
                  figuration 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).  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
           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 creden-
           tials 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 implements only a subset of the functionality
           available with SMTP: there is no support for TLS, and con-
           nections are cached in-process, making it ineffective when
           the client is used for multiple domains.

           Most  smtp_xxx  configuration  parameters have an lmtp_xxx
           "mirror" parameter for the equivalent LMTP  feature.  This
           document describes only those LMTP-related parameters that
           aren't simply "mirror" 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_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 Post-
                  fix  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  com-
                  mands as required by RFC 2821.

           smtp_reply_filter (empty)
                  A  mechanism  to transform replies from remote SMTP
                  servers one line at a time.

           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 com-
                  mand.

           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  key-
                  words  (pipelining,  starttls, auth, etc.) that the
                  Postfix  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 (pipelin-
                  ing, starttls, auth, etc.) that  the  Postfix  SMTP
                  client  will  ignore  in  the  EHLO response from a
                  remote SMTP server.

           smtp_generic_maps (empty)
                  Optional lookup tables that perform address rewrit-
                  ing  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 cer-
                  tificate 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 key-
                  words (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  (pipelin-
                  ing,  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  autho-
                  riZation ID (authzid); send only the SASL authenti-
                  Cation ID (authcid) plus the authcid'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)
                  An optional workaround for routers that  break  TCP
                  window scaling.

           Available in Postfix version 2.8 and later:

           smtp_dns_resolver_options (empty)
                  DNS Resolver options for the Postfix SMTP client.

    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 XFOR-
                  WARD 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 user-
                  name:password entry per remote hostname or  domain,
                  or sender address when sender-dependent authentica-
                  tion 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 implementation 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  mecha-
                  nisms.

           Available in Postfix version 2.3 and later:

           smtp_sender_dependent_authentication (no)
                  Enable sender-dependent authentication in the Post-
                  fix SMTP client; this is available only  with  SASL
                  authentication,   and   disables   SMTP  connection
                  caching to ensure that mail from different  senders
                  will use the appropriate credentials.

           smtp_sasl_path (empty)
                  Implementation-specific  information that the Post-
                  fix 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 authen-
                  tication failures with the same remote SMTP  server
                  hostname, username and password.

           smtp_sasl_auth_cache_time (90d)
                  The  maximal  age  of  an smtp_sasl_auth_cache_name
                  entry before it is removed.

           smtp_sasl_auth_soft_bounce (yes)
                  When a remote SMTP server rejects a SASL  authenti-
                  cation  request  with  a 535 reply code, defer mail
                  delivery instead of returning  mail  as  undeliver-
                  able.

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

           smtp_tls_security_level (empty)
                  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_secu-
           rity_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 hand-
                  shake procedures.

           smtp_tls_CAfile (empty)
                  A file  containing  CA  certificates  of  root  CAs
                  trusted  to sign either remote SMTP server certifi-
                  cates or intermediate CA certificates.

           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 manda-
                  tory 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,  when  TLS is not already enabled
                  for that server.

           smtp_tls_policy_maps (empty)
                  Optional lookup tables with the Postfix SMTP client
                  TLS security policy by next-hop destination; when a
                  non-empty value is specified,  this  overrides  the
                  obsolete smtp_tls_per_site parameter.

           smtp_tls_mandatory_protocols (SSLv3, TLSv1)
                  List  of  SSL/TLS  protocols  that the Postfix SMTP
                  client will use with mandatory TLS encryption.

           smtp_tls_scert_verifydepth (9)
                  The verification depth for remote SMTP server  cer-
                  tificates.

           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 ses-
                  sion 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_security_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_security_level = fingerprint).

           smtp_tls_fingerprint_digest (md5)
                  The message  digest  algorithm  used  to  construct
                  remote SMTP server certificate fingerprints.

           Available in Postfix version 2.6 and later:

           smtp_tls_protocols (!SSLv2)
                  List  of TLS protocols that the Postfix SMTP client
                  will exclude  or  include  with  opportunistic  TLS
                  encryption.

           smtp_tls_ciphers (export)
                  The  minimum TLS cipher grade that the Postfix SMTP
                  client will use with opportunistic TLS  encryption.

           smtp_tls_eccert_file (empty)
                  File with the Postfix SMTP client ECDSA certificate
                  in PEM format.

           smtp_tls_eckey_file ($smtp_tls_eccert_file)
                  File with the Postfix SMTP client ECDSA private key
                  in PEM format.

           Available in Postfix version 2.7 and later:

           smtp_tls_block_early_mail_reply (no)
                  Try  to  detect  a mail hijacking attack based on a
                  TLS protocol vulnerability  (CVE-2009-3555),  where
                  an  attacker  prepends  malicious HELO, MAIL, RCPT,
                  DATA commands to a Postfix SMTP client TLS session.

    OBSOLETE STARTTLS CONTROLS
           The  following configuration parameters exist for compati-
           bility 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 hostname.

           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_destina-
           tion_concurrency_limit)
                  The maximal number of parallel  deliveries  to  the
                  same  destination  via  the  smtp  message delivery
                  transport.

           smtp_destination_recipient_limit        ($default_destina-
           tion_recipient_limit)
                  The maximal number of recipients  per  message  for
                  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.

           lmtp_lhlo_timeout (300s)
                  The  LMTP  client  time  limit for sending the LHLO
                  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 (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 connection repeatedly.

           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.

           Available in Postfix version 2.3 and later:

           connection_cache_protocol_timeout (5s)
                  Time  limit  for  connection cache connect, send or
                  receive operations.

    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.

           internal_mail_filter_classes (empty)
                  What  categories of Postfix-generated mail are sub-
                  ject  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 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.

           delay_logging_resolution_limit (2)
                  The  maximal  number  of  digits  after the decimal
                  point when logging 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 sys-
                  tem 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.

           lmtp_assume_final (no)
                  When an  LMTP  server  announces  no  DSN  support,
                  assume that the server performs final delivery, and
                  send  "delivered"  delivery  status   notifications
                  instead of "relayed".

           lmtp_tcp_port (24)
                  The  default  TCP port that the Postfix LMTP client
                  connects to.

           max_idle (100s)
                  The maximum amount of time  that  an  idle  Postfix
                  daemon  process  waits  for  an incoming connection
                  before terminating voluntarily.

           max_use (100)
                  The maximal number of incoming connections  that  a
                  Postfix  daemon  process will service before termi-
                  nating 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 sys-
                  tem  receives  mail on by way of a proxy or network
                  address translation unit.

           smtp_address_preference (ipv6)
                  The address type ("ipv6", "ipv4" or "any") that the
                  Postfix SMTP client will try first, when a destina-
                  tion has IPv6 and  IPv4  addresses  with  equal  MX
                  preference.

           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 com-
                  mand.

           lmtp_lhlo_name ($myhostname)
                  The hostname to send in the LMTP LHLO command.

           smtp_host_lookup (dns)
                  What mechanisms 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, "postfix/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.

    SEE ALSO
           generic(5), output address rewriting
           header_checks(5), message header content inspection
           body_checks(5), body parts content inspection
           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
           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)