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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 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 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_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 message to the
              specified transport:destination.

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.

       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 protocol
              extensions 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)
              applications.

       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)
              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 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
              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 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
              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 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,
              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_security_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 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_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 authentication over unencrypted
              connections.

       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 (!SSLv2)
              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-
              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 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.

       Available in Postfix version 2.8 and later:

       tls_preempt_cipherlist (no)
              With SSLv3 and later, use the server's cipher preference order
              instead of the client's cipher preference 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 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
       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 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
              protocol 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.

       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, 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
              $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 $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
              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 limits are
       implemented 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 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 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, 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_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"
              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 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
              destinations matching $relay_domains.

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

       smtpd_null_access_lookup_key (<&lt;>&gt;)
              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
       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.

       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 "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
              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 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_recipient 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_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_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
              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 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_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 condition.

       unknown_helo_hostname_tempfail_action ($reject_tempfail_action)
              The Postfix SMTP server's action when
              reject_unknown_helo_hostname 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
              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 commands.

       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 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,
              "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
       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)