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SMTPD(8) System Manager's Manual 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 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 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 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 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 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.
  





  

  
Enable inter-operability with SMTP clients that implement an obsolete
      version of the AUTH command (RFC 4954).

  

  
Disable the SMTP VRFY command.

  

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

  

  
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 an address that ends in the "@" null domain as if the
      local hostname were specified, instead of rejecting the address as
      invalid.

  

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

  

  
What remote SMTP clients the Postfix SMTP server will not offer AUTH
      support to.




Available in Postfix version 2.2 and later:



  

  
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.

  

  
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.

  

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




Available in Postfix version 2.3 and later:



  

  
Force the Postfix SMTP server to issue a TLS session id, even when TLS
      session caching is turned off (smtpd_tls_session_cache_database is
    empty).




Available in Postfix version 2.6 and later:



  

  
An optional workaround for routers that break TCP window scaling.








ADDRESS REWRITING CONTROLS




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



  

  
Enable or disable recipient validation, built-in content filtering, or
      address mapping.




Available in Postfix version 2.2 and later:



  

  
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.



  

  
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 Postfix.
    See the SMTPD_PROXY_README document for details on how to configure and
    operate this feature.



  

  
The hostname and TCP port of the mail filtering proxy server.

  

  
How the Postfix SMTP server announces itself to the proxy filter.

  

  
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.



  

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

  

  
The mail filter protocol version and optional protocol extensions for
      communication with a Milter application; prior to Postfix 2.6 the default
      protocol is 2.

  

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

  

  
The {daemon_name} macro value for Milter (mail filter) applications.

  

  
The {v} macro value for Milter (mail filter) applications.

  

  
The time limit for connecting to a Milter (mail filter) application, and
      for negotiating protocol options.

  

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

  

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

  

  
The macros that are sent to Milter (mail filter) applications after
      completion of an SMTP connection.

  

  
The macros that are sent to Milter (mail filter) applications after the
      SMTP HELO or EHLO command.

  

  
The macros that are sent to Milter (mail filter) applications after the
      SMTP MAIL FROM command.

  

  
The macros that are sent to Milter (mail filter) applications after the
      SMTP RCPT TO command.

  

  
The macros that are sent to version 4 or higher Milter (mail filter)
      applications after the SMTP DATA command.

  

  
The macros that are sent to version 3 or higher Milter (mail filter)
      applications after an unknown SMTP command.

  

  
The macros that are sent to Milter (mail filter) applications after the
      end of the message header.

  

  
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:



  

  
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:



  

  
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.



  

  
Enable inter-operability with SMTP clients that implement an obsolete
      version of the AUTH command (RFC 4954).

  

  
Enable SASL authentication in the Postfix SMTP server.

  

  
The name of the Postfix SMTP server's local SASL authentication
    realm.

  

  
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.

  

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




Available in Postfix version 2.1 and later:



  

  
What remote SMTP clients the Postfix SMTP server will not offer AUTH
      support to.




Available in Postfix version 2.1 and 2.2:



  

  
The application name that the Postfix SMTP server uses for SASL server
      initialization.




Available in Postfix version 2.3 and later:



  

  
Report the SASL authenticated user name in the smtpd(8) Received
      message header.

  

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

  

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




Available in Postfix version 2.5 and later:



  

  
Search path for Cyrus SASL application configuration 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.



  

  
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.

  

  
The SASL authentication security options that the Postfix SMTP server uses
      for TLS encrypted SMTP sessions.

  

  
The time limit for Postfix SMTP server write and read operations during
      TLS startup and shutdown handshake procedures.

  

  
A file containing (PEM format) CA certificates of root CAs trusted to sign
      either remote SMTP client certificates or intermediate CA
    certificates.

  

  
A directory containing (PEM format) CA certificates of root CAs trusted to
      sign either remote SMTP client certificates or intermediate CA
      certificates.

  

  
Force the Postfix SMTP server to issue a TLS session id, even when TLS
      session caching is turned off (smtpd_tls_session_cache_database is
    empty).

  

  
Ask a remote SMTP client for a client certificate.

  

  
When TLS encryption is optional in the Postfix SMTP server, do not
      announce or accept SASL authentication over unencrypted connections.

  

  
The verification depth for remote SMTP client certificates.

  

  
File with the Postfix SMTP server RSA certificate in PEM format.

  

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

  

  
File with the Postfix SMTP server DSA certificate in PEM format.

  

  
File with DH parameters that the Postfix SMTP server should use with EDH
      ciphers.

  

  
File with DH parameters that the Postfix SMTP server should use with EDH
      ciphers.

  

  
File with the Postfix SMTP server DSA private key in PEM format.

  

  
File with the Postfix SMTP server RSA private key in PEM format.

  

  
Enable additional Postfix SMTP server logging of TLS activity.

  

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

  

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

  

  
The SSL/TLS protocols accepted by the Postfix SMTP server with mandatory
      TLS encryption.

  

  
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.

  

  
With mandatory TLS encryption, require a trusted remote SMTP client
      certificate in order to allow TLS connections to proceed.

  

  
Name of the file containing the optional Postfix SMTP server TLS session
      cache.

  

  
The expiration time of Postfix SMTP server TLS session cache
    information.

  

  
Run the Postfix SMTP server in the non-standard "wrapper" mode,
      instead of using the STARTTLS command.

  

  
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).

  

  
The OpenSSL cipherlist for "HIGH" grade ciphers.

  

  
The OpenSSL cipherlist for "MEDIUM" or higher grade
    ciphers.

  

  
The OpenSSL cipherlist for "LOW" or higher grade ciphers.

  

  
The OpenSSL cipherlist for "EXPORT" or higher grade
    ciphers.

  

  
The OpenSSL cipherlist for "NULL" grade ciphers that provide
      authentication without encryption.




Available in Postfix version 2.5 and later:



  

  
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:



  

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

  

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

  

  
File with the Postfix SMTP server ECDSA certificate in PEM format.

  

  
File with the Postfix SMTP server ECDSA private key in PEM format.

  

  
The Postfix SMTP server security grade for ephemeral elliptic-curve
      Diffie-Hellman (EECDH) key exchange.

  

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

  

  
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.



  

  
Opportunistic TLS: announce STARTTLS support to SMTP clients, but do not
      require that clients use TLS encryption.

  

  
Mandatory TLS: announce STARTTLS support to SMTP clients, and require that
      clients use TLS encryption.

  

  
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.



  

  
The two default VERP delimiter characters.

  

  
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:



  

  
What SMTP clients are allowed to specify the XVERP command.




Available in Postfix version 2.1 and later:



  

  
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.



  

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

  

  
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.

  

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

  

  
What categories of Postfix-generated mail are subject to before-queue
      content inspection by non_smtpd_milters, header_checks and
    body_checks.

  

  
The list of error classes that are reported to the postmaster.

  

  
Safety net to keep mail queued that would otherwise be returned to the
      sender.




Available in Postfix version 2.1 and later:



  

  
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.



  

  
Display the name of the recipient table in the "User unknown"
      responses.

  

  
Optional address mapping lookup tables for message headers and
    envelopes.

  

  
Optional address mapping lookup tables for envelope and header recipient
      addresses.




Parameters concerning known/unknown local recipients:



  

  
The list of domains that are delivered via the $local_transport mail
      delivery transport.

  

  
The network interface addresses that this mail system receives mail
    on.

  

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

  

  
The Internet protocols Postfix will attempt to use when making or
      accepting connections.

  

  
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.

  

  
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:



  

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

  

  
Optional lookup tables with all valid addresses in the domains that match
      $relay_domains.

  

  
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:



  

  
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.

  

  
Optional lookup tables that alias specific mail addresses or domains to
      other local or remote address.

  

  
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:



  

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

  

  
Optional lookup tables with all valid addresses in the domains that match
      $virtual_mailbox_domains.

  

  
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.



  

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

  

  
The minimal amount of free space in bytes in the queue file system that is
      needed to receive mail.

  

  
The maximal size in bytes of a message, including envelope
    information.

  

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

  

  
The time limit for sending a Postfix SMTP server response and for
      receiving a remote SMTP client request.

  

  
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:



  

  
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
    implemented in co-operation with the anvil(8) service, and are
    available in Postfix version 2.2 and later.



  

  
How many simultaneous connections any client is allowed to make to this
      service.

  

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

  

  
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.

  

  
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.

  

  
Clients that are excluded from connection count, connection rate, or SMTP
      request rate restrictions.




Available in Postfix version 2.3 and later:



  

  
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.



  

  
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.

  

  
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.

  

  
The maximal number of errors a remote SMTP client is allowed to make
      without delivering mail.

  

  
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:



  

  
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.



  

  
The time after which an idle SMTPD policy service connection is
    closed.

  

  
The time after which an active SMTPD policy service connection is
    closed.

  

  
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.



  

  
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.

  

  
What Postfix features match subdomains of "domain.tld"
      automatically, instead of requiring an explicit ".domain.tld"
      pattern.

  

  
Optional SMTP server access restrictions in the context of a client SMTP
      connection request.

  

  
Require that a remote SMTP client introduces itself at the beginning of an
      SMTP session with the HELO or EHLO command.

  

  
Optional restrictions that the Postfix SMTP server applies in the context
      of the SMTP HELO command.

  

  
Optional restrictions that the Postfix SMTP server applies in the context
      of the MAIL FROM command.

  

  
The access restrictions that the Postfix SMTP server applies in the
      context of the RCPT TO command.

  

  
Optional SMTP server access restrictions in the context of a client ETRN
      request.

  

  
Forward mail with sender-specified routing (user[@%!]remote[@%!]site) from
      untrusted clients to destinations matching $relay_domains.

  

  
User-defined aliases for groups of access restrictions.

  

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

  

  
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:



  

  
Optional access restrictions that the Postfix SMTP server applies in the
      context of the SMTP DATA command.

  

  
What characters are allowed in $name expansions of RBL reply
    templates.




Available in Postfix version 2.1 and later:



  

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

  

  
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:



  

  
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 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
    information about how to configure and operate the Postfix sender/recipient
    address verification service.



  

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

  

  
The delay between queries for the completion of an address verification
      request in progress.

  

  
The sender address to use in address verification probes; prior to Postfix
      2.5 the default was "postmaster".

  

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

  

  
The numerical Postfix SMTP server response when a recipient address is
      rejected by the reject_unverified_recipient restriction.




Available in Postfix version 2.6 and later:



  

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

  

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

  

  
The Postfix SMTP server's reply when rejecting mail with
      reject_unverified_sender.

  

  
The Postfix SMTP server's reply when rejecting mail with
      reject_unverified_recipient.

  

  
The Postfix SMTP server's action when reject_unverified_sender fails due
      to a temporary error condition.

  

  
The Postfix SMTP server's action when reject_unverified_recipient fails
      due to a temporary error condition.








ACCESS CONTROL RESPONSES




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



  

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

  

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

  

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

  

  
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_recipient restriction.

  

  
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.

  

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

  

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

  

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

  

  
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.

  

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

  

  
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:



  

  
The default SMTP server response template for a request that is rejected
      by an RBL-based restriction.

  

  
The numerical Postfix SMTP server response code when a remote SMTP client
      request is blocked by the reject_multi_recipient_bounce restriction.

  

  
Optional lookup tables with RBL response templates.




Available in Postfix version 2.6 and later:



  

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

  

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

  

  
The Postfix SMTP server's action when reject_unknown_helo_hostname fails
      due to an temporary error condition.

  

  
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





  

  
The default location of the Postfix main.cf and master.cf configuration
      files.

  

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

  

  
The location of all postfix administrative commands.

  

  
The sender address of postmaster notifications that are generated by the
      mail system.

  

  
The time limit for sending or receiving information over an internal
      communication channel.

  

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

  

  
The UNIX system account that owns the Postfix queue and most Postfix
      daemon processes.

  

  
The maximum amount of time that an idle Postfix daemon process waits for
      an incoming connection before terminating voluntarily.

  

  
The maximal number of incoming connections that a Postfix daemon process
      will service before terminating voluntarily.

  

  
The internet hostname of this mail system.

  

  
The list of "trusted" SMTP clients that have more privileges
      than "strangers".

  

  
The domain name that locally-posted mail appears to come from, and that
      locally posted mail is delivered to.

  

  
The process ID of a Postfix command or daemon process.

  

  
The process name of a Postfix command or daemon process.

  

  
The location of the Postfix top-level queue directory.

  

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

  

  
The text that follows the 220 status code in the SMTP greeting
    banner.

  

  
The syslog facility of Postfix logging.

  

  
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:



  

  
List of commands that causes the Postfix SMTP server to immediately
      terminate the session with a 221 code.




Available in Postfix version 2.5 and later:



  

  
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