SMTPD(8)                                                              SMTPD(8)



NAME
       smtpd - Postfix SMTP server

SYNOPSIS
       smtpd [generic Postfix daemon options]

       sendmail -bs

DESCRIPTION
       The  SMTP  server accepts network connection requests and performs zero
       or more SMTP transactions per connection.   Each  received  message  is
       piped  through  the  cleanup(8) daemon, and is placed into the incoming
       queue as one single queue file.  For this mode of operation,  the  pro-
       gram expects to be run from the master(8) process manager.

       Alternatively,  the SMTP server be can run in stand-alone mode; this is
       traditionally obtained with "sendmail -bs".  When the SMTP server  runs
       stand-alone  with  non  $mail_owner  privileges,  it receives mail even
       while the mail system is not running, deposits messages  directly  into
       the  maildrop queue, and disables the SMTP server's access policies. As
       of Postfix version 2.3, the SMTP server refuses to  receive  mail  from
       the network when it runs with non $mail_owner privileges.

       The  SMTP  server  implements  a  variety  of  policies  for connection
       requests, and for parameters given to HELO, ETRN, MAIL FROM,  VRFY  and
       RCPT TO commands. They are detailed below and in the main.cf configura-
       tion file.

SECURITY
       The SMTP server is moderately  security-sensitive.  It  talks  to  SMTP
       clients  and  to DNS servers on the network. The SMTP server can be run
       chrooted at fixed low privilege.

STANDARDS
       RFC 821 (SMTP protocol)
       RFC 1123 (Host requirements)
       RFC 1652 (8bit-MIME transport)
       RFC 1869 (SMTP service extensions)
       RFC 1870 (Message Size Declaration)
       RFC 1985 (ETRN command)
       RFC 2034 (SMTP Enhanced Error Codes)
       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 3848 (ESMTP Transmission Types)
       RFC 4954 (AUTH command)

DIAGNOSTICS
       Problems and transactions are logged to syslogd(8).

       Depending on the setting of the notify_classes parameter, the  postmas-
       ter  is  notified of bounces, protocol problems, policy violations, and
       of other trouble.

CONFIGURATION PARAMETERS
       Changes to main.cf are picked up automatically, as  smtpd(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
       The  following  parameters  work  around implementation errors in other
       software, and/or allow you to override standards in  order  to  prevent
       undesirable use.

       broken_sasl_auth_clients (no)
              Enable  inter-operability  with  SMTP  clients that implement an
              obsolete version of the AUTH command (RFC 4954).

       disable_vrfy_command (no)
              Disable the SMTP VRFY command.

       smtpd_noop_commands (empty)
              List of commands that the Postfix SMTP server  replies  to  with
              "250  Ok",  without doing any syntax checks and without changing
              state.

       strict_rfc821_envelopes (no)
              Require that addresses received in SMTP MAIL FROM  and  RCPT  TO
              commands  are  enclosed with <>, and that those addresses do not
              contain RFC 822 style comments or phrases.

       Available in Postfix version 2.1 and later:

       resolve_null_domain (no)
              Resolve an address that ends in the "@" null domain  as  if  the
              local  hostname were specified, instead of rejecting the address
              as invalid.

       smtpd_reject_unlisted_sender (no)
              Request that the Postfix SMTP server rejects mail  from  unknown
              sender  addresses,  even when no explicit reject_unlisted_sender
              access restriction is specified.

       smtpd_sasl_exceptions_networks (empty)
              What remote SMTP clients the Postfix SMTP server will not  offer
              AUTH support to.

       Available in Postfix version 2.2 and later:

       smtpd_discard_ehlo_keyword_address_maps (empty)
              Lookup  tables,  indexed by the remote SMTP client address, with
              case insensitive lists of EHLO keywords  (pipelining,  starttls,
              auth,  etc.)  that  the  SMTP  server  will not send in the EHLO
              response to a remote SMTP client.

       smtpd_discard_ehlo_keywords (empty)
              A case insensitive list of EHLO keywords (pipelining,  starttls,
              auth,  etc.)  that  the  SMTP  server  will not send in the EHLO
              response to a remote SMTP client.

       smtpd_delay_open_until_valid_rcpt (yes)
              Postpone the start of an SMTP mail  transaction  until  a  valid
              RCPT TO command is received.

       Available in Postfix version 2.3 and later:

       smtpd_tls_always_issue_session_ids (yes)
              Force  the  Postfix  SMTP server to issue a TLS session id, even
              when  TLS  session  caching  is   turned   off   (smtpd_tls_ses-
              sion_cache_database is empty).

       Available in Postfix version 2.6 and later:

       tcp_windowsize (0)
              An  optional  workaround for routers that break TCP window scal-
              ing.

ADDRESS REWRITING CONTROLS
       See the ADDRESS_REWRITING_README document for a detailed discussion  of
       Postfix address rewriting.

       receive_override_options (empty)
              Enable or disable recipient validation, built-in content filter-
              ing, or address mapping.

       Available in Postfix version 2.2 and later:

       local_header_rewrite_clients (permit_inet_interfaces)
              Rewrite message header addresses in mail from these clients  and
              update incomplete addresses with the domain name in $myorigin or
              $mydomain; either  don't  rewrite  message  headers  from  other
              clients at all, or rewrite message headers and update incomplete
              addresses with the domain  specified  in  the  remote_header_re-
              write_domain parameter.

AFTER QUEUE EXTERNAL CONTENT INSPECTION CONTROLS
       As  of  version  1.0,  Postfix can be configured to send new mail to an
       external content filter AFTER the mail is queued. This  content  filter
       is  expected to inject mail back into a (Postfix or other) MTA for fur-
       ther delivery. See the FILTER_README document for details.

       content_filter (empty)
              The name of a mail delivery transport that filters mail after it
              is queued.

BEFORE QUEUE EXTERNAL CONTENT INSPECTION CONTROLS
       As  of  version  2.1, the Postfix SMTP server can be configured to send
       incoming mail to a real-time SMTP-based content filter BEFORE  mail  is
       queued.  This content filter is expected to inject mail back into Post-
       fix.  See the SMTPD_PROXY_README document for details on how to config-
       ure and operate this feature.

       smtpd_proxy_filter (empty)
              The hostname and TCP port of the mail filtering proxy server.

       smtpd_proxy_ehlo ($myhostname)
              How  the  Postfix SMTP server announces itself to the proxy fil-
              ter.

       smtpd_proxy_timeout (100s)
              The time limit for connecting to a proxy filter and for  sending
              or receiving information.

BEFORE QUEUE MILTER CONTROLS
       As of version 2.3, Postfix supports the Sendmail version 8 Milter (mail
       filter) protocol. These content filters run outside Postfix.  They  can
       inspect  the  SMTP  command  stream  and  the  message content, and can
       request modifications before mail is queued. For details see  the  MIL-
       TER_README document.

       smtpd_milters (empty)
              A  list  of  Milter (mail filter) applications for new mail that
              arrives via the Postfix smtpd(8) server.

       milter_protocol (6)
              The mail filter protocol version and  optional  protocol  exten-
              sions  for  communication  with  a  Milter application; prior to
              Postfix 2.6 the default protocol is 2.

       milter_default_action (tempfail)
              The default action when a Milter (mail  filter)  application  is
              unavailable or mis-configured.

       milter_macro_daemon_name ($myhostname)
              The  {daemon_name} macro value for Milter (mail filter) applica-
              tions.

       milter_macro_v ($mail_name $mail_version)
              The {v} macro value for Milter (mail filter) applications.

       milter_connect_timeout (30s)
              The time limit for connecting to a Milter (mail filter) applica-
              tion, and for negotiating protocol options.

       milter_command_timeout (30s)
              The  time  limit  for  sending an SMTP command to a Milter (mail
              filter) application, and for receiving the response.

       milter_content_timeout (300s)
              The time limit for sending message content  to  a  Milter  (mail
              filter) application, and for receiving the response.

       milter_connect_macros (see 'postconf -d' output)
              The  macros  that  are sent to Milter (mail filter) applications
              after completion of an SMTP connection.

       milter_helo_macros (see 'postconf -d' output)
              The macros that are sent to Milter  (mail  filter)  applications
              after the SMTP HELO or EHLO command.

       milter_mail_macros (see 'postconf -d' output)
              The  macros  that  are sent to Milter (mail filter) applications
              after the SMTP MAIL FROM command.

       milter_rcpt_macros (see 'postconf -d' output)
              The macros that are sent to Milter  (mail  filter)  applications
              after the SMTP RCPT TO command.

       milter_data_macros (see 'postconf -d' output)
              The  macros  that  are  sent to version 4 or higher Milter (mail
              filter) applications after the SMTP DATA command.

       milter_unknown_command_macros (see 'postconf -d' output)
              The macros that are sent to version 3  or  higher  Milter  (mail
              filter) applications after an unknown SMTP command.

       milter_end_of_header_macros (see 'postconf -d' output)
              The  macros  that  are sent to Milter (mail filter) applications
              after the end of the message header.

       milter_end_of_data_macros (see 'postconf -d' output)
              The macros that are sent to Milter  (mail  filter)  applications
              after the message end-of-data.

GENERAL CONTENT INSPECTION CONTROLS
       The  following parameters are applicable for both built-in and external
       content filters.

       Available in Postfix version 2.1 and later:

       receive_override_options (empty)
              Enable or disable recipient validation, built-in content filter-
              ing, or address mapping.

EXTERNAL CONTENT INSPECTION CONTROLS
       The  following  parameters  are  applicable  for  both before-queue and
       after-queue content filtering.

       Available in Postfix version 2.1 and later:

       smtpd_authorized_xforward_hosts (empty)
              What SMTP clients are allowed to use the XFORWARD feature.

SASL AUTHENTICATION CONTROLS
       Postfix SASL support (RFC 4954) can be used to authenticate remote SMTP
       clients  to  the  Postfix  SMTP server, and to authenticate the Postfix
       SMTP client to a remote SMTP server.  See the SASL_README document  for
       details.

       broken_sasl_auth_clients (no)
              Enable  inter-operability  with  SMTP  clients that implement an
              obsolete version of the AUTH command (RFC 4954).

       smtpd_sasl_auth_enable (no)
              Enable SASL authentication in the Postfix SMTP server.

       smtpd_sasl_local_domain (empty)
              The name of the Postfix SMTP server's local SASL  authentication
              realm.

       smtpd_sasl_security_options (noanonymous)
              Postfix SMTP server SASL security options; as of Postfix 2.3 the
              list of available features depends on the SASL server  implemen-
              tation that is selected with smtpd_sasl_type.

       smtpd_sender_login_maps (empty)
              Optional  lookup table with the SASL login names that own sender
              (MAIL FROM) addresses.

       Available in Postfix version 2.1 and later:

       smtpd_sasl_exceptions_networks (empty)
              What remote SMTP clients the Postfix SMTP server will not  offer
              AUTH support to.

       Available in Postfix version 2.1 and 2.2:

       smtpd_sasl_application_name (smtpd)
              The  application name that the Postfix SMTP server uses for SASL
              server initialization.

       Available in Postfix version 2.3 and later:

       smtpd_sasl_authenticated_header (no)
              Report the SASL authenticated user name in the smtpd(8) Received
              message header.

       smtpd_sasl_path (smtpd)
              Implementation-specific information that the Postfix SMTP server
              passes through  to  the  SASL  plug-in  implementation  that  is
              selected with smtpd_sasl_type.

       smtpd_sasl_type (cyrus)
              The  SASL  plug-in  type that the Postfix SMTP server should use
              for authentication.

       Available in Postfix version 2.5 and later:

       cyrus_sasl_config_path (empty)
              Search path for Cyrus SASL application configuration files, cur-
              rently used only to locate the $smtpd_sasl_path.conf file.

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

       smtpd_tls_security_level (empty)
              The SMTP TLS security level for the Postfix SMTP server; when  a
              non-empty value is specified, this overrides the obsolete param-
              eters smtpd_use_tls and smtpd_enforce_tls.

       smtpd_sasl_tls_security_options ($smtpd_sasl_security_options)
              The SASL authentication security options that the  Postfix  SMTP
              server uses for TLS encrypted SMTP sessions.

       smtpd_starttls_timeout (300s)
              The time limit for Postfix SMTP server write and read operations
              during TLS startup and shutdown handshake procedures.

       smtpd_tls_CAfile (empty)
              A file containing (PEM  format)  CA  certificates  of  root  CAs
              trusted to sign either remote SMTP client certificates or inter-
              mediate CA certificates.

       smtpd_tls_CApath (empty)
              A directory containing (PEM format) CA certificates of root  CAs
              trusted to sign either remote SMTP client certificates or inter-
              mediate CA certificates.

       smtpd_tls_always_issue_session_ids (yes)
              Force the Postfix SMTP server to issue a TLS  session  id,  even
              when   TLS   session   caching  is  turned  off  (smtpd_tls_ses-
              sion_cache_database is empty).

       smtpd_tls_ask_ccert (no)
              Ask a remote SMTP client for a client certificate.

       smtpd_tls_auth_only (no)
              When TLS encryption is optional in the Postfix SMTP  server,  do
              not announce or accept SASL authentication over unencrypted con-
              nections.

       smtpd_tls_ccert_verifydepth (9)
              The verification depth for remote SMTP client certificates.

       smtpd_tls_cert_file (empty)
              File with the Postfix SMTP server RSA certificate in PEM format.

       smtpd_tls_exclude_ciphers (empty)
              List  of ciphers or cipher types to exclude from the SMTP server
              cipher list at all TLS security levels.

       smtpd_tls_dcert_file (empty)
              File with the Postfix SMTP server DSA certificate in PEM format.

       smtpd_tls_dh1024_param_file (empty)
              File  with DH parameters that the Postfix SMTP server should use
              with EDH ciphers.

       smtpd_tls_dh512_param_file (empty)
              File with DH parameters that the Postfix SMTP server should  use
              with EDH ciphers.

       smtpd_tls_dkey_file ($smtpd_tls_dcert_file)
              File with the Postfix SMTP server DSA private key in PEM format.

       smtpd_tls_key_file ($smtpd_tls_cert_file)
              File with the Postfix SMTP server RSA private key in PEM format.

       smtpd_tls_loglevel (0)
              Enable additional Postfix SMTP server logging of TLS activity.

       smtpd_tls_mandatory_ciphers (medium)
              The  minimum  TLS cipher grade that the Postfix SMTP server will
              use with mandatory TLS encryption.

       smtpd_tls_mandatory_exclude_ciphers (empty)
              Additional list of ciphers or cipher types to exclude  from  the
              SMTP server cipher list at mandatory TLS security levels.

       smtpd_tls_mandatory_protocols (SSLv3, TLSv1)
              The  SSL/TLS  protocols accepted by the Postfix SMTP server with
              mandatory TLS encryption.

       smtpd_tls_received_header (no)
              Request that the Postfix SMTP server produces Received:  message
              headers  that  include information about the protocol and cipher
              used, as well as the client CommonName  and  client  certificate
              issuer CommonName.

       smtpd_tls_req_ccert (no)
              With  mandatory  TLS  encryption,  require a trusted remote SMTP
              client certificate in order to allow TLS connections to proceed.

       smtpd_tls_session_cache_database (empty)
              Name of the file containing the optional Postfix SMTP server TLS
              session cache.

       smtpd_tls_session_cache_timeout (3600s)
              The expiration time of Postfix SMTP  server  TLS  session  cache
              information.

       smtpd_tls_wrappermode (no)
              Run  the Postfix SMTP server in the non-standard "wrapper" mode,
              instead of using the STARTTLS command.

       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 2.5 and later:

       smtpd_tls_fingerprint_digest (md5)
              The  message  digest algorithm used to construct client-certifi-
              cate    fingerprints    for    check_ccert_access    and    per-
              mit_tls_clientcerts.

       Available in Postfix version 2.6 and later:

       smtpd_tls_protocols (empty)
              List  of TLS protocols that the Postfix SMTP server will exclude
              or include with opportunistic TLS encryption.

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

       smtpd_tls_eccert_file (empty)
              File  with the Postfix SMTP server ECDSA certificate in PEM for-
              mat.

       smtpd_tls_eckey_file ($smtpd_tls_eccert_file)
              File with the Postfix SMTP server ECDSA private key in PEM  for-
              mat.

       smtpd_tls_eecdh_grade (see 'postconf -d' output)
              The  Postfix  SMTP server security grade for ephemeral elliptic-
              curve Diffie-Hellman (EECDH) key exchange.

       tls_eecdh_strong_curve (prime256v1)
              The elliptic curve used by the SMTP server for  sensibly  strong
              ephemeral ECDH key exchange.

       tls_eecdh_ultra_curve (secp384r1)
              The  elliptic curve used by the SMTP server for maximally strong
              ephemeral ECDH key exchange.

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.

       smtpd_use_tls (no)
              Opportunistic TLS: announce STARTTLS support  to  SMTP  clients,
              but do not require that clients use TLS encryption.

       smtpd_enforce_tls (no)
              Mandatory  TLS:  announce  STARTTLS support to SMTP clients, and
              require that clients use TLS encryption.

       smtpd_tls_cipherlist (empty)
              Obsolete Postfix < 2.3 control for the Postfix SMTP  server  TLS
              cipher list.

VERP SUPPORT CONTROLS
       With  VERP  style delivery, each recipient of a message receives a cus-
       tomized copy of the message with his/her own recipient address  encoded
       in the envelope sender address.  The VERP_README file describes config-
       uration and operation details of Postfix support for variable  envelope
       return  path addresses.  VERP style delivery is requested with the SMTP
       XVERP command or with the "sendmail  -V"  command-line  option  and  is
       available in Postfix version 1.1 and later.

       default_verp_delimiters (+=)
              The two default VERP delimiter characters.

       verp_delimiter_filter (-=+)
              The  characters  Postfix accepts as VERP delimiter characters on
              the Postfix sendmail(1) command line and in SMTP commands.

       Available in Postfix version 1.1 and 2.0:

       authorized_verp_clients ($mynetworks)
              What SMTP clients are allowed to specify the XVERP command.

       Available in Postfix version 2.1 and later:

       smtpd_authorized_verp_clients ($authorized_verp_clients)
              What SMTP clients are allowed to specify the XVERP command.

TROUBLE SHOOTING CONTROLS
       The DEBUG_README document describes how to debug parts of  the  Postfix
       mail  system.  The  methods  vary from making the software log a lot of
       detail, to running some daemon processes under control of a call tracer
       or debugger.

       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 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.

       soft_bounce (no)
              Safety net to keep mail queued that would otherwise be  returned
              to the sender.

       Available in Postfix version 2.1 and later:

       smtpd_authorized_xclient_hosts (empty)
              What SMTP clients are allowed to use the XCLIENT feature.

KNOWN VERSUS UNKNOWN RECIPIENT CONTROLS
       As  of  Postfix  version  2.0, the SMTP server rejects mail for unknown
       recipients. This prevents the mail queue from clogging up with undeliv-
       erable  MAILER-DAEMON messages. Additional information on this topic is
       in the LOCAL_RECIPIENT_README and ADDRESS_CLASS_README documents.

       show_user_unknown_table_name (yes)
              Display the name of the recipient table in  the  "User  unknown"
              responses.

       canonical_maps (empty)
              Optional  address  mapping lookup tables for message headers and
              envelopes.

       recipient_canonical_maps (empty)
              Optional address mapping lookup tables for envelope  and  header
              recipient addresses.

       Parameters concerning known/unknown local recipients:

       mydestination ($myhostname, localhost.$mydomain, localhost)
              The  list of domains that are delivered via the $local_transport
              mail delivery transport.

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

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

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

       local_recipient_maps (proxy:unix:passwd.byname $alias_maps)
              Lookup tables with all names or addresses of local recipients: a
              recipient address is local when its domain  matches  $mydestina-
              tion, $inet_interfaces or $proxy_interfaces.

       unknown_local_recipient_reject_code (550)
              The numerical Postfix SMTP server response code when a recipient
              address is local, and $local_recipient_maps specifies a list  of
              lookup tables that does not match the recipient.

       Parameters concerning known/unknown recipients of relay destinations:

       relay_domains ($mydestination)
              What  destination  domains  (and subdomains thereof) this system
              will relay mail to.

       relay_recipient_maps (empty)
              Optional lookup tables with all valid addresses in  the  domains
              that match $relay_domains.

       unknown_relay_recipient_reject_code (550)
              The  numerical  Postfix  SMTP server reply code when a recipient
              address matches $relay_domains, and relay_recipient_maps  speci-
              fies  a  list of lookup tables that does not match the recipient
              address.

       Parameters  concerning  known/unknown  recipients  in   virtual   alias
       domains:

       virtual_alias_domains ($virtual_alias_maps)
              Postfix  is  final destination for the specified list of virtual
              alias domains, that is, domains  for  which  all  addresses  are
              aliased to addresses in other local or remote domains.

       virtual_alias_maps ($virtual_maps)
              Optional  lookup  tables  that  alias specific mail addresses or
              domains to other local or remote address.

       unknown_virtual_alias_reject_code (550)
              The SMTP server reply code  when  a  recipient  address  matches
              $virtual_alias_domains, and $virtual_alias_maps specifies a list
              of lookup tables that does not match the recipient address.

       Parameters  concerning  known/unknown  recipients  in  virtual  mailbox
       domains:

       virtual_mailbox_domains ($virtual_mailbox_maps)
              Postfix  is final destination for the specified list of domains;
              mail is  delivered  via  the  $virtual_transport  mail  delivery
              transport.

       virtual_mailbox_maps (empty)
              Optional  lookup  tables with all valid addresses in the domains
              that match $virtual_mailbox_domains.

       unknown_virtual_mailbox_reject_code (550)
              The SMTP server reply code  when  a  recipient  address  matches
              $virtual_mailbox_domains,  and $virtual_mailbox_maps specifies a
              list of lookup tables that does not match the recipient address.

RESOURCE AND RATE CONTROLS
       The following parameters limit resource usage by the SMTP server and/or
       control client request rates.

       line_length_limit (2048)
              Upon input, long lines are chopped up into  pieces  of  at  most
              this length; upon delivery, long lines are reconstructed.

       queue_minfree (0)
              The minimal amount of free space in bytes in the queue file sys-
              tem that is needed to receive mail.

       message_size_limit (10240000)
              The maximal size in  bytes  of  a  message,  including  envelope
              information.

       smtpd_recipient_limit (1000)
              The  maximal  number  of recipients that the Postfix SMTP server
              accepts per message delivery request.

       smtpd_timeout (normal: 300s, stress: 10s)
              The time limit for sending a Postfix SMTP  server  response  and
              for receiving a remote SMTP client request.

       smtpd_history_flush_threshold (100)
              The  maximal  number of lines in the Postfix SMTP server command
              history before it is flushed upon receipt of EHLO, RSET, or  end
              of DATA.

       Available in Postfix version 2.3 and later:

       smtpd_peername_lookup (yes)
              Attempt  to  look up the remote SMTP client hostname, and verify
              that the name matches the client IP address.

       The per SMTP client connection count and request rate limits are imple-
       mented  in co-operation with the anvil(8) service, and are available in
       Postfix version 2.2 and later.

       smtpd_client_connection_count_limit (50)
              How many simultaneous connections any client is allowed to  make
              to this service.

       smtpd_client_connection_rate_limit (0)
              The  maximal number of connection attempts any client is allowed
              to make to this service per time unit.

       smtpd_client_message_rate_limit (0)
              The maximal number of message delivery requests that any  client
              is  allowed to make to this service per time unit, regardless of
              whether or not Postfix actually accepts those messages.

       smtpd_client_recipient_rate_limit (0)
              The maximal number of recipient addresses  that  any  client  is
              allowed  to  send  to  this service per time unit, regardless of
              whether or not Postfix actually accepts those recipients.

       smtpd_client_event_limit_exceptions ($mynetworks)
              Clients that are  excluded  from  connection  count,  connection
              rate, or SMTP request rate restrictions.

       Available in Postfix version 2.3 and later:

       smtpd_client_new_tls_session_rate_limit (0)
              The  maximal  number of new (i.e., uncached) TLS sessions that a
              remote SMTP client is allowed to negotiate with this service per
              time unit.

TARPIT CONTROLS
       When  a  remote  SMTP  client makes errors, the Postfix SMTP server can
       insert delays before responding. This can help to  slow  down  run-away
       software.   The  behavior is controlled by an error counter that counts
       the number of errors within an SMTP session that a client makes without
       delivering mail.

       smtpd_error_sleep_time (1s)
              With  Postfix  version  2.1  and later: the SMTP server response
              delay after a client has made more than  $smtpd_soft_error_limit
              errors,  and  fewer than $smtpd_hard_error_limit errors, without
              delivering mail.

       smtpd_soft_error_limit (10)
              The number of errors a remote SMTP client  is  allowed  to  make
              without  delivering  mail  before  the Postfix SMTP server slows
              down all its responses.

       smtpd_hard_error_limit (normal: 20, stress: 1)
              The maximal number of errors a remote SMTP client is allowed  to
              make without delivering mail.

       smtpd_junk_command_limit (normal: 100, stress: 1)
              The  number  of  junk commands (NOOP, VRFY, ETRN or RSET) that a
              remote SMTP client can  send  before  the  Postfix  SMTP  server
              starts to increment the error counter with each junk command.

       Available in Postfix version 2.1 and later:

       smtpd_recipient_overshoot_limit (1000)
              The  number  of recipients that a remote SMTP client can send in
              excess  of  the  limit  specified  with  $smtpd_recipient_limit,
              before  the Postfix SMTP server increments the per-session error
              count for each excess recipient.

ACCESS POLICY DELEGATION CONTROLS
       As of version 2.1, Postfix can be configured to delegate access  policy
       decisions  to  an  external  server that runs outside Postfix.  See the
       file SMTPD_POLICY_README for more information.

       smtpd_policy_service_max_idle (300s)
              The time after which an idle SMTPD policy service connection  is
              closed.

       smtpd_policy_service_max_ttl (1000s)
              The  time  after which an active SMTPD policy service connection
              is closed.

       smtpd_policy_service_timeout (100s)
              The time limit for connecting to, writing to or receiving from a
              delegated SMTPD policy server.

ACCESS CONTROLS
       The  SMTPD_ACCESS_README document gives an introduction to all the SMTP
       server access control features.

       smtpd_delay_reject (yes)
              Wait   until   the   RCPT   TO   command    before    evaluating
              $smtpd_client_restrictions,     $smtpd_helo_restrictions     and
              $smtpd_sender_restrictions,  or  wait  until  the  ETRN  command
              before       evaluating      $smtpd_client_restrictions      and
              $smtpd_helo_restrictions.

       parent_domain_matches_subdomains (see 'postconf -d' output)
              What Postfix features match subdomains of "domain.tld" automati-
              cally, instead of requiring an explicit ".domain.tld" pattern.

       smtpd_client_restrictions (empty)
              Optional  SMTP  server  access  restrictions in the context of a
              client SMTP connection request.

       smtpd_helo_required (no)
              Require that a remote  SMTP  client  introduces  itself  at  the
              beginning of an SMTP session with the HELO or EHLO command.

       smtpd_helo_restrictions (empty)
              Optional  restrictions  that  the Postfix SMTP server applies in
              the context of the SMTP HELO command.

       smtpd_sender_restrictions (empty)
              Optional restrictions that the Postfix SMTP  server  applies  in
              the context of the MAIL FROM command.

       smtpd_recipient_restrictions (permit_mynetworks, reject_unauth_destina-
       tion)
              The  access restrictions that the Postfix SMTP server applies in
              the context of the RCPT TO command.

       smtpd_etrn_restrictions (empty)
              Optional SMTP server access restrictions in  the  context  of  a
              client ETRN request.

       allow_untrusted_routing (no)
              Forward       mail       with      sender-specified      routing
              (user[@%!]remote[@%!]site) from untrusted  clients  to  destina-
              tions matching $relay_domains.

       smtpd_restriction_classes (empty)
              User-defined aliases for groups of access restrictions.

       smtpd_null_access_lookup_key (<>)
              The  lookup  key  to be used in SMTP access(5) tables instead of
              the null sender address.

       permit_mx_backup_networks (empty)
              Restrict the use of the permit_mx_backup SMTP access feature  to
              only domains whose primary MX hosts match the listed networks.

       Available in Postfix version 2.0 and later:

       smtpd_data_restrictions (empty)
              Optional  access  restrictions  that  the  Postfix  SMTP  server
              applies in the context of the SMTP DATA command.

       smtpd_expansion_filter (see 'postconf -d' output)
              What characters are allowed in $name  expansions  of  RBL  reply
              templates.

       Available in Postfix version 2.1 and later:

       smtpd_reject_unlisted_sender (no)
              Request  that  the Postfix SMTP server rejects mail from unknown
              sender addresses, even when no  explicit  reject_unlisted_sender
              access restriction is specified.

       smtpd_reject_unlisted_recipient (yes)
              Request  that  the  Postfix SMTP server rejects mail for unknown
              recipient     addresses,     even     when      no      explicit
              reject_unlisted_recipient access restriction is specified.

       Available in Postfix version 2.2 and later:

       smtpd_end_of_data_restrictions (empty)
              Optional  access  restrictions  that  the  Postfix  SMTP  server
              applies in the context of the SMTP END-OF-DATA command.

SENDER AND RECIPIENT ADDRESS VERIFICATION CONTROLS
       Postfix version 2.1 introduces sender and recipient  address  verifica-
       tion.  This feature is implemented by sending probe email messages that
       are  not  actually  delivered.   This  feature  is  requested  via  the
       reject_unverified_sender    and    reject_unverified_recipient   access
       restrictions.  The status of verification probes is maintained  by  the
       verify(8)  server.  See the file ADDRESS_VERIFICATION_README for infor-
       mation about how to configure and operate the Postfix  sender/recipient
       address verification service.

       address_verify_poll_count (3)
              How many times to query the verify(8) service for the completion
              of an address verification request in progress.

       address_verify_poll_delay (3s)
              The delay between queries for the completion of an address veri-
              fication request in progress.

       address_verify_sender ($double_bounce_sender)
              The  sender address to use in address verification probes; prior
              to Postfix 2.5 the default was "postmaster".

       unverified_sender_reject_code (450)
              The numerical Postfix SMTP server response code when a recipient
              address is rejected by the reject_unverified_sender restriction.

       unverified_recipient_reject_code (450)
              The numerical Postfix SMTP  server  response  when  a  recipient
              address  is rejected by the reject_unverified_recipient restric-
              tion.

       Available in Postfix version 2.6 and later:

       unverified_sender_defer_code (450)
              The numerical Postfix SMTP server response code  when  a  sender
              address probe fails due to a temporary error condition.

       unverified_recipient_defer_code (450)
              The  numerical  Postfix  SMTP  server  response when a recipient
              address probe fails due to a temporary error condition.

       unverified_sender_reject_reason (empty)
              The  Postfix  SMTP  server's  reply  when  rejecting  mail  with
              reject_unverified_sender.

       unverified_recipient_reject_reason (empty)
              The  Postfix  SMTP  server's  reply  when  rejecting  mail  with
              reject_unverified_recipient.

       unverified_sender_tempfail_action ($reject_tempfail_action)
              The Postfix SMTP server's action  when  reject_unverified_sender
              fails due to a temporary error condition.

       unverified_recipient_tempfail_action ($reject_tempfail_action)
              The  Postfix SMTP server's action when reject_unverified_recipi-
              ent fails due to a temporary error condition.

ACCESS CONTROL RESPONSES
       The following parameters control numerical SMTP reply codes and/or text
       responses.

       access_map_reject_code (554)
              The numerical Postfix SMTP server response code for an access(5)
              map "reject" action.

       defer_code (450)
              The numerical Postfix SMTP server response code  when  a  remote
              SMTP client request is rejected by the "defer" restriction.

       invalid_hostname_reject_code (501)
              The  numerical Postfix SMTP server response code when the client
              HELO  or   EHLO   command   parameter   is   rejected   by   the
              reject_invalid_helo_hostname restriction.

       maps_rbl_reject_code (554)
              The  numerical  Postfix  SMTP server response code when a remote
              SMTP  client  request  is  blocked  by  the   reject_rbl_client,
              reject_rhsbl_client, reject_rhsbl_sender or reject_rhsbl_recipi-
              ent restriction.

       non_fqdn_reject_code (504)
              The numerical Postfix SMTP  server  reply  code  when  a  client
              request   is   rejected  by  the  reject_non_fqdn_helo_hostname,
              reject_non_fqdn_sender or reject_non_fqdn_recipient restriction.

       plaintext_reject_code (450)
              The  numerical  Postfix SMTP server response code when a request
              is rejected by the reject_plaintext_session restriction.

       reject_code (554)
              The numerical Postfix SMTP server response code  when  a  remote
              SMTP client request is rejected by the "reject" restriction.

       relay_domains_reject_code (554)
              The  numerical  Postfix  SMTP server response code when a client
              request is rejected by the  reject_unauth_destination  recipient
              restriction.

       unknown_address_reject_code (450)
              The numerical Postfix SMTP server response code when a sender or
              recipient      address      is       rejected       by       the
              reject_unknown_sender_domain  or reject_unknown_recipient_domain
              restriction.

       unknown_client_reject_code (450)
              The numerical Postfix SMTP server response code  when  a  client
              without  valid  address  <=>  name  mapping  is  rejected by the
              reject_unknown_client_hostname restriction.

       unknown_hostname_reject_code (450)
              The numerical Postfix SMTP server response code when  the  host-
              name  specified with the HELO or EHLO command is rejected by the
              reject_unknown_helo_hostname restriction.

       Available in Postfix version 2.0 and later:

       default_rbl_reply (see 'postconf -d' output)
              The default SMTP server response template for a request that  is
              rejected by an RBL-based restriction.

       multi_recipient_bounce_reject_code (550)
              The  numerical  Postfix  SMTP server response code when a remote
              SMTP client  request  is  blocked  by  the  reject_multi_recipi-
              ent_bounce restriction.

       rbl_reply_maps (empty)
              Optional lookup tables with RBL response templates.

       Available in Postfix version 2.6 and later:

       access_map_defer_code (450)
              The numerical Postfix SMTP server response code for an access(5)
              map   "defer"    action,    including    "defer_if_permit"    or
              "defer_if_reject".

       reject_tempfail_action (defer_if_permit)
              The  Postfix SMTP server's action when a reject-type restriction
              fails due to a temporary error condition.

       unknown_helo_hostname_tempfail_action ($reject_tempfail_action)
              The Postfix SMTP server's action when  reject_unknown_helo_host-
              name fails due to an temporary error condition.

       unknown_address_tempfail_action ($reject_tempfail_action)
              The       Postfix       SMTP      server's      action      when
              reject_unknown_sender_domain or  reject_unknown_recipient_domain
              fail due to a temporary error condition.

MISCELLANEOUS CONTROLS
       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.

       command_directory (see 'postconf -d' output)
              The location of all postfix administrative commands.

       double_bounce_sender (double-bounce)
              The  sender  address of postmaster notifications that are gener-
              ated by the mail system.

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

       mail_name (Postfix)
              The  mail system name that is displayed in Received: headers, in
              the SMTP greeting banner, and in bounced mail.

       mail_owner (postfix)
              The UNIX system account that owns the  Postfix  queue  and  most
              Postfix daemon processes.

       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 terminating voluntarily.

       myhostname (see 'postconf -d' output)
              The internet hostname of this mail system.

       mynetworks (see 'postconf -d' output)
              The list of "trusted" SMTP clients  that  have  more  privileges
              than "strangers".

       myorigin ($myhostname)
              The  domain  name that locally-posted mail appears to come from,
              and that locally posted mail is delivered to.

       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.

       queue_directory (see 'postconf -d' output)
              The location of the Postfix top-level queue directory.

       recipient_delimiter (empty)
              The  separator  between  user  names  and   address   extensions
              (user+foo).

       smtpd_banner ($myhostname ESMTP $mail_name)
              The  text  that follows the 220 status code in the SMTP greeting
              banner.

       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 in Postfix version 2.2 and later:

       smtpd_forbidden_commands (CONNECT, GET, POST)
              List of commands that causes the Postfix SMTP server to  immedi-
              ately terminate the session with a 221 code.

       Available in Postfix version 2.5 and later:

       smtpd_client_port_logging (no)
              Enable logging of the remote SMTP client port in addition to the
              hostname and IP address.

SEE ALSO
       anvil(8), connection/rate limiting
       cleanup(8), message canonicalization
       tlsmgr(8), TLS session and PRNG management
       trivial-rewrite(8), address resolver
       verify(8), address verification service
       postconf(5), configuration parameters
       master(5), generic daemon options
       master(8), process manager
       syslogd(8), system logging

README FILES
       Use "postconf readme_directory" or "postconf html_directory" to  locate
       this information.
       ADDRESS_CLASS_README, blocking unknown hosted or relay recipients
       ADDRESS_REWRITING_README Postfix address manipulation
       FILTER_README, external after-queue content filter
       LOCAL_RECIPIENT_README, blocking unknown local recipients
       MILTER_README, before-queue mail filter applications
       SMTPD_ACCESS_README, built-in access policies
       SMTPD_POLICY_README, external policy server
       SMTPD_PROXY_README, external before-queue content filter
       SASL_README, Postfix SASL howto
       TLS_README, Postfix STARTTLS howto
       VERP_README, Postfix XVERP extension
       XCLIENT_README, Postfix XCLIENT extension
       XFORWARD_README, Postfix XFORWARD extension

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

       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 support by:
       Victor Duchovni
       Morgan Stanley



                                                                      SMTPD(8)

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©1996-2014 Modified for NetBSD by Kimmo Suominen