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) dae-
       mon, and is placed into the incoming queue as  one  single
       queue  file.   For  this  mode  of  operation, the program
       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  con-
       nection  requests, and for parameters given to HELO, ETRN,
       MAIL FROM, VRFY and RCPT TO commands.  They  are  detailed
       below and in the main.cf configuration 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 Status 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 postmaster 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  com-
              ments 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  key-
              words  (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 (pipelin-
              ing, 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 ses-
              sion id, even when TLS session  caching  is  turned
              off (smtpd_tls_session_cache_database is empty).

       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 2.7 and later:

       smtpd_command_filter (empty)
              A mechanism to transform commands from remote  SMTP
              clients.

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 filtering, 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_rewrite_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  further  delivery.
       See the FILTER_README document for details.

       content_filter (empty)
              After  the  message is queued, send the entire mes-
              sage to the specified transport:destination.

BEFORE QUEUE EXTERNAL CONTENT INSPECTION CONTROLS
       As of version 2.1, the Postfix SMTP server can be  config-
       ured  to send incoming mail to a real-time SMTP-based con-
       tent filter BEFORE mail is queued.  This content filter is
       expected  to  inject  mail  back  into  Postfix.   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 filter.

       smtpd_proxy_options (empty)
              List  of  options that control how the Postfix SMTP
              server communicates  with  a  before-queue  content
              filter.

       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  MILTER_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 pro-
              tocol extensions for communication  with  a  Milter
              application;  prior to Postfix 2.6 the default pro-
              tocol 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 fil-
              ter) applications.

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

       milter_connect_timeout (30s)
              The  time  limit  for  connecting to a Milter (mail
              filter) application, 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  connec-
              tion.

       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 filtering, 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  authenti-
       cate  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 implementation 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  Post-
              fix  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  configura-
              tion  files,  currently  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 parameters smtpd_use_tls and
              smtpd_enforce_tls.

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

       smtpd_starttls_timeout (see 'postconf -d' output)
              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 intermediate 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  intermediate  CA  certifi-
              cates.

       smtpd_tls_always_issue_session_ids (yes)
              Force  the  Postfix SMTP server to issue a TLS ses-
              sion id, even when TLS session  caching  is  turned
              off (smtpd_tls_session_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 authentica-
              tion over unencrypted connections.

       smtpd_tls_ccert_verifydepth (9)
              The verification depth for remote SMTP client  cer-
              tificates.

       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  manda-
              tory 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 ses-
              sion cache information.

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

       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-certificate         fingerprints         for
              check_ccert_access and permit_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 format.

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

       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 sen-
              sibly strong ephemeral ECDH key exchange.

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

       Available in Postfix version 2.8 and later:

       tls_preempt_cipherlist (no)
              With SSLv3 and later, use the server's cipher pref-
              erence order instead of the client's cipher prefer-
              ence order.

       tls_disable_workarounds (see 'postconf -d' output)
              List  or  bit-mask  of  OpenSSL bug work-arounds to
              disable.

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.

       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 encryp-
              tion.

       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 customized copy of the message with his/her own
       recipient  address encoded in the envelope sender address.
       The VERP_README file describes configuration 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 pro-
       cesses 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 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.

       smtpd_reject_footer (empty)
              Optional information that is  appended  after  each
              SMTP server 4XX or 5XX response.

       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  undeliverable  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,  local-
       host)
              The  list  of  domains  that  are delivered via the
              $local_transport mail delivery transport.

       inet_interfaces (all)
              The network interface addresses that this mail sys-
              tem receives mail on.

       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.

       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 $mydestination, $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  specifies  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    $vir-
              tual_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  $vir-
              tual_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    $vir-
              tual_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 system 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, overload: 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 lim-
       its are implemented in co-operation with the anvil(8) ser-
       vice, 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
              smtpd_client_*_count/rate_limit 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 ses-
              sions that a remote SMTP client is allowed to nego-
              tiate 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 con-
       trolled 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, overload: 1)
              The maximal number of errors a remote  SMTP  client
              is allowed to make without delivering mail.

       smtpd_junk_command_limit (normal: 100, overload: 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_restric-
              tions and $smtpd_sender_restrictions, or wait until
              the     ETRN     command     before      evaluating
              $smtpd_client_restrictions and $smtpd_helo_restric-
              tions.

       parent_domain_matches_subdomains (see 'postconf  -d'  out-
       put)
              What   Postfix   features   match   subdomains   of
              "domain.tld" automatically, 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
              with the HELO or EHLO command  before  sending  the
              MAIL  command  or  other commands that require EHLO
              negotiation.

       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_destination)
              The  access  restrictions  that  the  Postfix  SMTP
              server  applies  in the context of the RCPT TO com-
              mand.

       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 destinations matching $relay_domains.

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

       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 com-
              mand.

       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 restric-
              tion 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  verification.   This  feature  is  implemented by
       sending probe email messages that are not actually  deliv-
       ered.   This  feature  is requested via the reject_unveri-
       fied_sender   and    reject_unverified_recipient    access
       restrictions.   The status of verification probes is main-
       tained by the verify(8) server.  See the file ADDRESS_VER-
       IFICATION_README  for  information  about how to configure
       and operate the Postfix sender/recipient address verifica-
       tion service.

       address_verify_poll_count (normal: 3, overload: 1)
              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 verification 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 "post-
              master".

       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_unveri-
              fied_recipient restriction.

       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 tempo-
              rary 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_temp-
       fail_action)
              The Postfix SMTP server's action when reject_unver-
              ified_sender  fails due to a temporary error condi-
              tion.

       unverified_recipient_tempfail_action        ($reject_temp-
       fail_action)
              The Postfix SMTP server's action when reject_unver-
              ified_recipient fails due to a temporary error con-
              dition.

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_reverse_client, reject_rhsbl_sender or
              reject_rhsbl_recipient 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_plain-
              text_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 map-
              ping is rejected by the reject_unknown_client_host-
              name restriction.

       unknown_hostname_reject_code (450)
              The  numerical  Postfix  SMTP  server response code
              when the hostname 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 restric-
              tion.

       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_recipient_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  condi-
              tion.

       unknown_helo_hostname_tempfail_action       ($reject_temp-
       fail_action)
              The    Postfix    SMTP    server's    action   when
              reject_unknown_helo_hostname fails due to an tempo-
              rary 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 tem-
              porary error condition.

MISCELLANEOUS CONTROLS
       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.

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

       double_bounce_sender (double-bounce)
              The sender address of postmaster notifications that
              are generated 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  termi-
              nating 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 deliv-
              ered 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  direc-
              tory.

       recipient_delimiter (empty)
              The separator between user names and address exten-
              sions (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, "postfix/smtpd".

       Available in Postfix version 2.2 and later:

       smtpd_forbidden_commands (CONNECT, GET, POST)
              List of commands that cause the Postfix SMTP server
              to immediately 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
       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)