smtpd

title: smtpd(8)

text:
# 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

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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 3030 (CHUNKING without BINARYMIME)
RFC 3207 (STARTTLS command)
RFC 3461 (SMTP DSN extension)
RFC 3463 (Enhanced status codes)
RFC 3848 (ESMTP transmission types)
RFC 4409 (Message submission)
RFC 4954 (AUTH command)
RFC 5321 (SMTP protocol)
RFC 6531 (Internationalized SMTP)
RFC 6533 (Internationalized Delivery Status Notifications)
RFC 7505 ("Null MX" No Service Resource Record)
```

## DIAGNOSTICS

Problems and transactions are logged to syslogd(8) or postlogd(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

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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

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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 interoperability with remote SMTP clients that implement an obsolete version of the AUTH command (RFC 4954).

disable_vrfy_command (yes)

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:

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 Postfix 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 Postfix 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.

Available in Postfix version 2.9 and later:

smtpd_per_record_deadline (normal: no, overload: yes)

Change the behavior of the smtpd_timeout and smtpd_starttls_timeout time limits, from a time limit per read or write system call, to a time limit to send or receive a complete record (an SMTP command line, SMTP response line, SMTP message content line, or TLS protocol message).

Available in Postfix version 3.0 and later:

smtpd_dns_reply_filter (empty)

Optional filter for Postfix SMTP server DNS lookup results.

Available in Postfix version 3.6 and later:

smtpd_relay_before_recipient_restrictions (see 'postconf -d' output)

Evaluate smtpd_relay_restrictions before smtpd_recipient_restrictions.

known_tcp_ports (lmtp=24, smtp=25, smtps=submissions=465, submission=587)

Optional setting that avoids lookups in the services(5) database.

## ADDRESS REWRITING CONTROLS

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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.

## BEFORE-SMTPD PROXY AGENT

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Available in Postfix version 2.10 and later:

smtpd_upstream_proxy_protocol (empty)

The name of the proxy protocol used by an optional before-smtpd proxy agent.

smtpd_upstream_proxy_timeout (5s)

The time limit for the proxy protocol specified with the smtpd_upstream_proxy_protocol parameter.

## AFTER QUEUE EXTERNAL CONTENT INSPECTION CONTROLS

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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

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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

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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) response is unavailable (for example, bad Postfix configuration or Milter failure).

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.

Available in Postfix version 3.1 and later:

milter_macro_defaults (empty)

Optional list of name=value pairs that specify default values for arbitrary macros that Postfix may send to Milter applications.

Available in Postfix version 3.2 and later:

smtpd_milter_maps (empty)

Lookup tables with Milter settings per remote SMTP client IP address.

## GENERAL CONTENT INSPECTION CONTROLS

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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

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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 remote SMTP clients are allowed to use the XFORWARD feature.

## SASL AUTHENTICATION CONTROLS

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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 interoperability with remote 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 the 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.

Available in Postfix version 2.11 and later:

smtpd_sasl_service (smtp)

The service name that is passed to the SASL plug-in that is selected with smtpd_sasl_type and smtpd_sasl_path.

Available in Postfix version 3.4 and later:

smtpd_sasl_response_limit (12288)

The maximum length of a SASL client's response to a server challenge.

Available in Postfix 3.6 and later:

smtpd_sasl_mechanism_filter (!external, static:rest)

If non-empty, a filter for the SASL mechanism names that the Postfix SMTP server will announce in the EHLO response.

## STARTTLS SUPPORT CONTROLS

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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 non-export EDH ciphers.

smtpd_tls_dh512_param_file (empty)

File with DH parameters that the Postfix SMTP server should use with export-grade 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 Postfix SMTP server cipher list at mandatory TLS security levels.

smtpd_tls_mandatory_protocols (see 'postconf -d' output)

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 remote SMTP 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_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 (see 'postconf -d' output)

The OpenSSL cipherlist for "high" grade ciphers.

tls_medium_cipherlist (see 'postconf -d' output)

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

tls_low_cipherlist (see 'postconf -d' output)

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

tls_export_cipherlist (see 'postconf -d' output)

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 (see 'postconf -d' output)

The message digest algorithm to construct remote SMTP client-certificate fingerprints or public key fingerprints (Postfix 2.9 and later) for check_ccert_access and permit_tls_clientcerts.

Available in Postfix version 2.6 and later:

smtpd_tls_protocols (see postconf -d output)

TLS protocols accepted by the Postfix SMTP server with opportunistic TLS encryption.

smtpd_tls_ciphers (medium)

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 Postfix SMTP server for sensibly strong ephemeral ECDH key exchange.

tls_eecdh_ultra_curve (secp384r1)

The elliptic curve used by the Postfix 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 Postfix SMTP server's cipher preference order instead of the remote client's cipher preference order.

tls_disable_workarounds (see 'postconf -d' output)

List or bit-mask of OpenSSL bug work-arounds to disable.

Available in Postfix version 2.11 and later:

tlsmgr_service_name (tlsmgr)

The name of the tlsmgr(8) service entry in master.cf.

Available in Postfix version 3.0 and later:

tls_session_ticket_cipher (Postfix >= 3.0: aes-256-cbc, Postfix < 3.0: aes-128-cbc)

Algorithm used to encrypt RFC5077 TLS session tickets.

Available in Postfix version 3.2 and later:

tls_eecdh_auto_curves (see 'postconf -d' output)

The prioritized list of elliptic curves supported by the Postfix SMTP client and server.

Available in Postfix version 3.4 and later:

smtpd_tls_chain_files (empty)

List of one or more PEM files, each holding one or more private keys directly followed by a corresponding certificate chain.

tls_server_sni_maps (empty)

Optional lookup tables that map names received from remote SMTP clients via the TLS Server Name Indication (SNI) extension to the appropriate keys and certificate chains.

Available in Postfix 3.5, 3.4.6, 3.3.5, 3.2.10, 3.1.13 and later:

tls_fast_shutdown_enable (yes)

A workaround for implementations that hang Postfix while shutting down a TLS session, until Postfix times out.

Available in Postfix 3.5 and later:

info_log_address_format (external)

The email address form that will be used in non-debug logging (info, warning, etc.).

## OBSOLETE STARTTLS CONTROLS

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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 remote SMTP clients, but do not require that clients use TLS encryption.

smtpd_enforce_tls (no)

Mandatory TLS: announce STARTTLS support to remote 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.

## SMTPUTF8 CONTROLS

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Preliminary SMTPUTF8 support is introduced with Postfix 3.0.

smtputf8_enable (yes)

Enable preliminary SMTPUTF8 support for the protocols described in RFC 6531..6533.

strict_smtputf8 (no)

Enable stricter enforcement of the SMTPUTF8 protocol.

smtputf8_autodetect_classes (sendmail, verify)

Detect that a message requires SMTPUTF8 support for the specified mail origin classes.

Available in Postfix version 3.2 and later:

enable_idna2003_compatibility (no)

Enable 'transitional' compatibility between IDNA2003 and IDNA2008, when converting UTF-8 domain names to/from the ASCII form that is used for DNS lookups.

## VERP SUPPORT CONTROLS

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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 remote 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 remote SMTP clients are allowed to specify the XVERP command.

## TROUBLE SHOOTING CONTROLS

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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 nexthop destination, remote client or server name or network address matches a pattern given with the debug_peer_list parameter.

debug_peer_list (empty)

Optional list of nexthop destination, remote client or server name or network address patterns that, if matched, 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 Postfix 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 remote SMTP clients are allowed to use the XCLIENT feature.

Available in Postfix version 2.10 and later:

smtpd_log_access_permit_actions (empty)

Enable logging of the named "permit" actions in SMTP server access lists (by default, the SMTP server logs "reject" actions but not "permit" actions).

## KNOWN VERSUS UNKNOWN RECIPIENT CONTROLS

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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.

sender_canonical_maps (empty)

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

Parameters concerning known/unknown local recipients:

mydestination ($myhostname, localhost.$mydomain, localhost, $config_directory/mydestination)

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 (any)

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 (Postfix >= 3.0: empty, Postfix < 3.0: $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 Postfix 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 Postfix 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.

Available in Postfix version 2.9 and later:

smtpd_per_record_deadline (normal: no, overload: yes)

Change the behavior of the smtpd_timeout and smtpd_starttls_timeout time limits, from a time limit per read or write system call, to a time limit to send or receive a complete record (an SMTP command line, SMTP response line, SMTP message content line, or TLS protocol message).

Available in Postfix version 3.1 and later:

smtpd_client_auth_rate_limit (0)

The maximal number of AUTH commands that any client is allowed to send to this service per time unit, regardless of whether or not Postfix actually accepts those commands.

## 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.

Available in Postfix version 3.0 and later:

smtpd_policy_service_default_action (451 4.3.5 Server configuration problem)

The default action when an SMTPD policy service request fails.

smtpd_policy_service_request_limit (0)

The maximal number of requests per SMTPD policy service connection, or zero (no limit).

smtpd_policy_service_try_limit (2)

The maximal number of attempts to send an SMTPD policy service request before giving up.

smtpd_policy_service_retry_delay (1s)

The delay between attempts to resend a failed SMTPD policy service request.

Available in Postfix version 3.1 and later:

smtpd_policy_service_policy_context (empty)

Optional information that the Postfix SMTP server specifies in the "policy_context" attribute of a policy service request (originally, to share the same service endpoint among multiple check_policy_service clients).

## 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)

A list of Postfix features where the pattern "example.com" also matches subdomains of example.com, instead of requiring an explicit ".example.com" pattern.

smtpd_client_restrictions (empty)

Optional restrictions that the Postfix SMTP server applies in the context of a client connection request.

smtpd_helo_required (yes)

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 a client HELO command.

smtpd_sender_restrictions (empty)

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

smtpd_recipient_restrictions (see 'postconf -d' output)

Optional restrictions that the Postfix SMTP server applies in the context of a client RCPT TO command, after smtpd_relay_restrictions.

smtpd_etrn_restrictions (permit_mynetworks, reject)

Optional restrictions that the Postfix SMTP server applies in the context of a client ETRN command.

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 (<>)

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 (reject_unauth_pipelining)

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.

Available in Postfix version 2.10 and later:

smtpd_relay_restrictions (permit_mynetworks, permit_sasl_authenticated, defer_unauth_destination)

Access restrictions for mail relay control that the Postfix SMTP server applies in the context of the RCPT TO command, before smtpd_recipient_restrictions.

## 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.

Available with Postfix 2.9 and later:

address_verify_sender_ttl (0s)

The time between changes in the time-dependent portion of address verification probe sender addresses.

## 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 response code when the Postfix SMTP server rejects a sender or recipient address because its domain is unknown.

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 Postfix 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 a 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" remote 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 set of characters that can separate an email address localpart, user name, or a .forward file name from its extension.

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)

A prefix that is prepended to the process name in syslog records, so that, for example, "smtpd" becomes "prefix/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.

Available in Postfix 3.3 and later:

service_name (read-only)

The master.cf service name of a Postfix daemon process.

Available in Postfix 3.4 and later:

smtpd_reject_footer_maps (empty)

Lookup tables, indexed by the complete Postfix SMTP server 4xx or 5xx response, with reject footer templates.

## 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
postlogd(8), Postfix logging
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
BDAT_README, Postfix CHUNKING support
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
Wietse Venema
Google, Inc.
111 8th Avenue
New York, NY 10011, 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
```


spawn

package: postfix

title: spawn(8)

text:
# spawn(8)

## NAME
spawn - Postfix external command spawner

## SYNOPSIS

```
spawn [generic Postfix daemon options] command_attributes...
```

## DESCRIPTION

The spawn(8) daemon provides the Postfix equivalent of inetd. It listens on a port as specified in the Postfix master.cf file and spawns an external command whenever a connection is established. The connection can be made over local IPC (such as UNIX-domain sockets) or over non-local IPC (such as TCP sockets). The command´s standard input, output and error streams are connected directly to the communication endpoint.

This daemon expects to be run from the master(8) process manager.

## COMMAND ATTRIBUTE SYNTAX

```

```

The external command attributes are given in the master.cf file at the end of a service definition. The syntax is as follows:

user=username (required)

user=username:groupname

The external command is executed with the rights of the specified username. The software refuses to execute commands with root privileges, or with the privileges of the mail system owner. If groupname is specified, the corresponding group ID is used instead of the group ID of username.

argv=command... (required)

The command to be executed. This must be specified as the last command attribute. The command is executed directly, i.e. without interpretation of shell meta characters by a shell command interpreter.

## BUGS

In order to enforce standard Postfix process resource controls, the spawn(8) daemon runs only one external command at a time. As such, it presents a noticeable overhead by wasting precious process resources. The spawn(8) daemon is expected to be replaced by a more structural solution.

## DIAGNOSTICS

The spawn(8) daemon reports abnormal child exits. Problems are logged to syslogd(8) or postlogd(8).

## SECURITY

```

```

This program needs root privilege in order to execute external commands as the specified user. It is therefore security sensitive. However the spawn(8) daemon does not talk to the external command and thus is not vulnerable to data-driven attacks.

## CONFIGURATION PARAMETERS

```

```

Changes to main.cf are picked up automatically as spawn(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.

In the text below, transport is the first field of the entry in the master.cf file.

## RESOURCE AND RATE CONTROL

```

```

transport_time_limit ($command_time_limit)

A transport-specific override for the command_time_limit parameter value, where transport is the master.cf name of the message delivery transport.

## MISCELLANEOUS

```

```

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.

export_environment (see 'postconf -d' output)

The list of environment variables that a Postfix process will export to non-Postfix processes.

ipc_timeout (3600s)

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

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.

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.

syslog_facility (mail)

The syslog facility of Postfix logging.

syslog_name (see 'postconf -d' output)

A prefix that is prepended to the process name in syslog records, so that, for example, "smtpd" becomes "prefix/smtpd".

Available in Postfix 3.3 and later:

service_name (read-only)

The master.cf service name of a Postfix daemon process.

## SEE ALSO

```
postconf(5), configuration parameters
master(8), process manager
postlogd(8), Postfix logging
syslogd(8), system logging
```

## 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
Wietse Venema
Google, Inc.
111 8th Avenue
New York, NY 10011, USA
```


trivial-rewrite

title: trivial-rewrite(8)

text:
# trivial-rewrite(8)

## NAME
trivial-rewrite - Postfix address rewriting and resolving daemon

## SYNOPSIS

```
trivial-rewrite [generic Postfix daemon options]
```

## DESCRIPTION

The trivial-rewrite(8) daemon processes three types of client service requests:

rewrite context address

Rewrite an address to standard form, according to the address rewriting context:

local

Append the domain names specified with $myorigin or $mydomain to incomplete addresses; do swap_bangpath and allow_percent_hack processing as described below, and strip source routed addresses (@site,@site:user@domain) to user@domain form.

remote

Append the domain name specified with $remote_header_rewrite_domain to incomplete addresses. Otherwise the result is identical to that of the local address rewriting context. This prevents Postfix from appending the local domain to spam from poorly written remote clients.

resolve sender address

Resolve the address to a (transport, nexthop, recipient, flags) quadruple. The meaning of the results is as follows:

transport

The delivery agent to use. This is the first field of an entry in the master.cf file.

nexthop

The host to send to and optional delivery method information.

recipient

The envelope recipient address that is passed on to nexthop.

flags

The address class, whether the address requires relaying, whether the address has problems, and whether the request failed.

verify sender address

Resolve the address for address verification purposes.

## SERVER PROCESS MANAGEMENT

```

```

The trivial-rewrite(8) servers run under control by the Postfix master server. Each server can handle multiple simultaneous connections. When all servers are busy while a client connects, the master creates a new server process, provided that the trivial-rewrite server process limit is not exceeded. Each trivial-rewrite server terminates after serving at least $max_use clients of after $max_idle seconds of idle time.

## STANDARDS

```

```

None. The command does not interact with the outside world.

## SECURITY

```

```

The trivial-rewrite(8) daemon is not security sensitive. By default, this daemon does not talk to remote or local users. It can run at a fixed low privilege in a chrooted environment.

## DIAGNOSTICS

Problems and transactions are logged to syslogd(8) or postlogd(8).

## CONFIGURATION PARAMETERS

```

```

On busy mail systems a long time may pass before a main.cf change affecting trivial-rewrite(8) is picked up. 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

```

```

resolve_dequoted_address (yes)

Resolve a recipient address safely instead of correctly, by looking inside quotes.

Available with 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.

Available with Postfix version 2.3 and later:

resolve_numeric_domain (no)

Resolve "user@ipaddress" as "user@[ipaddress]", instead of rejecting the address as invalid.

Available with Postfix version 2.5 and later:

allow_min_user (no)

Allow a sender or recipient address to have `-' as the first character.

## ADDRESS REWRITING CONTROLS

```

```

myorigin ($myhostname)

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

allow_percent_hack (yes)

Enable the rewriting of the form "user%domain" to "user@domain".

append_at_myorigin (yes)

With locally submitted mail, append the string "@$myorigin" to mail addresses without domain information.

append_dot_mydomain (Postfix >= 3.0: no, Postfix < 3.0: yes)

With locally submitted mail, append the string ".$mydomain" to addresses that have no ".domain" information.

recipient_delimiter (empty)

The set of characters that can separate an email address localpart, user name, or a .forward file name from its extension.

swap_bangpath (yes)

Enable the rewriting of "site!user" into "user@site".

Available in Postfix 2.2 and later:

remote_header_rewrite_domain (empty)

Don't rewrite message headers from remote clients at all when this parameter is empty; otherwise, rewrite message headers and append the specified domain name to incomplete addresses.

## ROUTING CONTROLS

```

```

The following is applicable to Postfix version 2.0 and later. Earlier versions do not have support for: virtual_transport, relay_transport, virtual_alias_domains, virtual_mailbox_domains or proxy_interfaces.

local_transport (local:$myhostname)

The default mail delivery transport and next-hop destination for final delivery to domains listed with mydestination, and for [ipaddress] destinations that match $inet_interfaces or $proxy_interfaces.

virtual_transport (virtual)

The default mail delivery transport and next-hop destination for final delivery to domains listed with $virtual_mailbox_domains.

relay_transport (relay)

The default mail delivery transport and next-hop destination for remote delivery to domains listed with $relay_domains.

default_transport (smtp)

The default mail delivery transport and next-hop destination for destinations that do not match $mydestination, $inet_interfaces, $proxy_interfaces, $virtual_alias_domains, $virtual_mailbox_domains, or $relay_domains.

parent_domain_matches_subdomains (see 'postconf -d' output)

A list of Postfix features where the pattern "example.com" also matches subdomains of example.com, instead of requiring an explicit ".example.com" pattern.

relayhost (empty)

The next-hop destination(s) for non-local mail; overrides non-local domains in recipient addresses.

transport_maps (empty)

Optional lookup tables with mappings from recipient address to (message delivery transport, next-hop destination).

Available in Postfix version 2.3 and later:

sender_dependent_relayhost_maps (empty)

A sender-dependent override for the global relayhost parameter setting.

Available in Postfix version 2.5 and later:

empty_address_relayhost_maps_lookup_key (<>)

The sender_dependent_relayhost_maps search string that will be used instead of the null sender address.

Available in Postfix version 2.7 and later:

empty_address_default_transport_maps_lookup_key (<>)

The sender_dependent_default_transport_maps search string that will be used instead of the null sender address.

sender_dependent_default_transport_maps (empty)

A sender-dependent override for the global default_transport parameter setting.

## 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. By default, address verification probes use the same route as regular mail. To override specific aspects of message routing for address verification probes, specify one or more of the following:

address_verify_local_transport ($local_transport)

Overrides the local_transport parameter setting for address verification probes.

address_verify_virtual_transport ($virtual_transport)

Overrides the virtual_transport parameter setting for address verification probes.

address_verify_relay_transport ($relay_transport)

Overrides the relay_transport parameter setting for address verification probes.

address_verify_default_transport ($default_transport)

Overrides the default_transport parameter setting for address verification probes.

address_verify_relayhost ($relayhost)

Overrides the relayhost parameter setting for address verification probes.

address_verify_transport_maps ($transport_maps)

Overrides the transport_maps parameter setting for address verification probes.

Available in Postfix version 2.3 and later:

address_verify_sender_dependent_relayhost_maps ($sender_dependent_relayhost_maps)

Overrides the sender_dependent_relayhost_maps parameter setting for address verification probes.

Available in Postfix version 2.7 and later:

address_verify_sender_dependent_default_transport_maps ($sender_dependent_default_transport_maps)

Overrides the sender_dependent_default_transport_maps parameter setting for address verification probes.

## 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.

empty_address_recipient (MAILER-DAEMON)

The recipient of mail addressed to the null address.

ipc_timeout (3600s)

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

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.

relocated_maps (empty)

Optional lookup tables with new contact information for users or domains that no longer exist.

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.

show_user_unknown_table_name (yes)

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

syslog_facility (mail)

The syslog facility of Postfix logging.

syslog_name (see 'postconf -d' output)

A prefix that is prepended to the process name in syslog records, so that, for example, "smtpd" becomes "prefix/smtpd".

Available in Postfix version 2.0 and later:

helpful_warnings (yes)

Log warnings about problematic configuration settings, and provide helpful suggestions.

Available in Postfix 3.3 and later:

service_name (read-only)

The master.cf service name of a Postfix daemon process.

## SEE ALSO

```
postconf(5), configuration parameters
transport(5), transport table format
relocated(5), format of the "user has moved" table
master(8), process manager
postlogd(8), Postfix logging
syslogd(8), system logging
```

## README FILES

```

```

Use "postconf readme_directory" or "postconf html_directory" to locate this information.

```
ADDRESS_CLASS_README, Postfix address classes howto
ADDRESS_VERIFICATION_README, Postfix address verification
```

## 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
Wietse Venema
Google, Inc.
111 8th Avenue
New York, NY 10011, USA
```


verify

title: verify(8)

text:
# verify(8)

## NAME
verify - Postfix address verification server

## SYNOPSIS

```
verify [generic Postfix daemon options]
```

## DESCRIPTION

The verify(8) address verification server maintains a record of what recipient addresses are known to be deliverable or undeliverable.

Addresses are verified by injecting probe messages into the Postfix queue. Probe messages are run through all the routing and rewriting machinery except for final delivery, and are discarded rather than being deferred or bounced.

Address verification relies on the answer from the nearest MTA for the specified address, and will therefore not detect all undeliverable addresses.

The verify(8) server is designed to run under control by the Postfix master server. It maintains an optional persistent database. To avoid being interrupted by "postfix stop" in the middle of a database update, the process runs in a separate process group.

The verify(8) server implements the following requests:

update address status text

Update the status and text of the specified address.

query address

Look up the status and text for the specified address. If the status is unknown, a probe is sent and an "in progress" status is returned.

## SECURITY

```

```

The address verification server is not security-sensitive. It does not talk to the network, and it does not talk to local users. The verify server can run chrooted at fixed low privilege.

The address verification server can be coerced to store unlimited amounts of garbage. Limiting the cache expiry time trades one problem (disk space exhaustion) for another one (poor response time to client requests).

With Postfix version 2.5 and later, the verify(8) server no longer uses root privileges when opening the address_verify_map cache file. The file should now be stored under the Postfix-owned data_directory. As a migration aid, an attempt to open a cache file under a non-Postfix directory is redirected to the Postfix-owned data_directory, and a warning is logged.

## DIAGNOSTICS

Problems and transactions are logged to syslogd(8) or postlogd(8).

## BUGS

Address verification probe messages add additional traffic to the mail queue. Recipient verification may cause an increased load on down-stream servers in the case of a dictionary attack or a flood of backscatter bounces. Sender address verification may cause your site to be denylisted by some providers.

If the persistent database ever gets corrupted then the world comes to an end and human intervention is needed. This violates a basic Postfix principle.

## CONFIGURATION PARAMETERS

```

```

Changes to main.cf are not picked up automatically, as verify(8) processes are long-lived. Use the command "postfix reload" after a configuration change.

The text below provides only a parameter summary. See postconf(5) for more details including examples.

## PROBE MESSAGE CONTROLS

```

```

address_verify_sender ($double_bounce_sender)

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

Available with Postfix 2.9 and later:

address_verify_sender_ttl (0s)

The time between changes in the time-dependent portion of address verification probe sender addresses.

## CACHE CONTROLS

```

```

address_verify_map (see 'postconf -d' output)

Lookup table for persistent address verification status storage.

address_verify_positive_expire_time (31d)

The time after which a successful probe expires from the address verification cache.

address_verify_positive_refresh_time (7d)

The time after which a successful address verification probe needs to be refreshed.

address_verify_negative_cache (yes)

Enable caching of failed address verification probe results.

address_verify_negative_expire_time (3d)

The time after which a failed probe expires from the address verification cache.

address_verify_negative_refresh_time (3h)

The time after which a failed address verification probe needs to be refreshed.

Available with Postfix 2.7 and later:

address_verify_cache_cleanup_interval (12h)

The amount of time between verify(8) address verification database cleanup runs.

## PROBE MESSAGE ROUTING CONTROLS

```

```

By default, probe messages are delivered via the same route as regular messages. The following parameters can be used to override specific message routing mechanisms.

address_verify_relayhost ($relayhost)

Overrides the relayhost parameter setting for address verification probes.

address_verify_transport_maps ($transport_maps)

Overrides the transport_maps parameter setting for address verification probes.

address_verify_local_transport ($local_transport)

Overrides the local_transport parameter setting for address verification probes.

address_verify_virtual_transport ($virtual_transport)

Overrides the virtual_transport parameter setting for address verification probes.

address_verify_relay_transport ($relay_transport)

Overrides the relay_transport parameter setting for address verification probes.

address_verify_default_transport ($default_transport)

Overrides the default_transport parameter setting for address verification probes.

Available in Postfix 2.3 and later:

address_verify_sender_dependent_relayhost_maps ($sender_dependent_relayhost_maps)

Overrides the sender_dependent_relayhost_maps parameter setting for address verification probes.

Available in Postfix 2.7 and later:

address_verify_sender_dependent_default_transport_maps ($sender_dependent_default_transport_maps)

Overrides the sender_dependent_default_transport_maps parameter setting for address verification probes.

## SMTPUTF8 CONTROLS

```

```

Preliminary SMTPUTF8 support is introduced with Postfix 3.0.

smtputf8_autodetect_classes (sendmail, verify)

Detect that a message requires SMTPUTF8 support for the specified mail origin classes.

Available in Postfix version 3.2 and later:

enable_idna2003_compatibility (no)

Enable 'transitional' compatibility between IDNA2003 and IDNA2008, when converting UTF-8 domain names to/from the ASCII form that is used for DNS lookups.

## 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.

ipc_timeout (3600s)

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

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.

syslog_facility (mail)

The syslog facility of Postfix logging.

syslog_name (see 'postconf -d' output)

A prefix that is prepended to the process name in syslog records, so that, for example, "smtpd" becomes "prefix/smtpd".

Available in Postfix 3.3 and later:

service_name (read-only)

The master.cf service name of a Postfix daemon process.

## SEE ALSO

```
smtpd(8), Postfix SMTP server
cleanup(8), enqueue Postfix message
postconf(5), configuration parameters
postlogd(8), Postfix logging
syslogd(8), system logging
```

## README FILES

```

```

Use "postconf readme_directory" or "postconf html_directory" to locate this information.

```
ADDRESS_VERIFICATION_README, address verification howto
```

## LICENSE

```

```

The Secure Mailer license must be distributed with this software.

## HISTORY

This service was introduced with Postfix version 2.1.

## AUTHOR(S)

```
Wietse Venema
IBM T.J. Watson Research
P.O. Box 704
Yorktown Heights, NY 10598, USA
Wietse Venema
Google, Inc.
111 8th Avenue
New York, NY 10011, USA
```


virtual

title: virtual(8)

text:
# virtual(8)

## NAME
virtual - Postfix virtual domain mail delivery agent

## SYNOPSIS

```
virtual [generic Postfix daemon options]
```

## DESCRIPTION

The virtual(8) delivery agent is designed for virtual mail hosting services. Originally based on the Postfix local(8) delivery agent, this agent looks up recipients with map lookups of their full recipient address, instead of using hard-coded unix password file lookups of the address local part only.

This delivery agent only delivers mail. Other features such as mail forwarding, out-of-office notifications, etc., must be configured via virtual_alias maps or via similar lookup mechanisms.

## MAILBOX LOCATION

```

```

The mailbox location is controlled by the virtual_mailbox_base and virtual_mailbox_maps configuration parameters (see below). The virtual_mailbox_maps table is indexed by the recipient address as described under TABLE SEARCH ORDER below.

The mailbox pathname is constructed as follows:

```
  $virtual_mailbox_base/$virtual_mailbox_maps(recipient)
```

where recipient is the full recipient address.

## UNIX MAILBOX FORMAT

```

```

When the mailbox location does not end in /, the message is delivered in UNIX mailbox format. This format stores multiple messages in one textfile.

The virtual(8) delivery agent prepends a "From sender time_stamp" envelope header to each message, prepends a Delivered-To: message header with the envelope recipient address, prepends an X-Original-To: header with the recipient address as given to Postfix, prepends a Return-Path: message header with the envelope sender address, prepends a > character to lines beginning with "From ", and appends an empty line.

The mailbox is locked for exclusive access while delivery is in progress. In case of problems, an attempt is made to truncate the mailbox to its original length.

## QMAIL MAILDIR FORMAT

```

```

When the mailbox location ends in /, the message is delivered in qmail maildir format. This format stores one message per file.

The virtual(8) delivery agent prepends a Delivered-To: message header with the final envelope recipient address, prepends an X-Original-To: header with the recipient address as given to Postfix, and prepends a Return-Path: message header with the envelope sender address.

By definition, maildir format does not require application-level file locking during mail delivery or retrieval.

## MAILBOX OWNERSHIP

```

```

Mailbox ownership is controlled by the virtual_uid_maps and virtual_gid_maps lookup tables, which are indexed with the full recipient address. Each table provides a string with the numerical user and group ID, respectively.

The virtual_minimum_uid parameter imposes a lower bound on numerical user ID values that may be specified in any virtual_uid_maps.

## CASE FOLDING

```

```

All delivery decisions are made using the full recipient address, folded to lower case. See also the next section for a few exceptions with optional address extensions.

## TABLE SEARCH ORDER

```

```

Normally, a lookup table is specified as a text file that serves as input to the postmap(1) command. The result, an indexed file in dbm or db format, is used for fast searching by the mail system.

The search order is as follows. The search stops upon the first successful lookup.

- When the recipient has an optional address extension the user+extension@domain.tld address is looked up first. With Postfix versions before 2.1, the optional address extension is always ignored.

- The user@domain.tld address, without address extension, is looked up next.

- Finally, the recipient @domain is looked up.

When the table is provided via other means such as NIS, LDAP or SQL, the same lookups are done as for ordinary indexed files.

Alternatively, a table can be provided as a regular-expression map where patterns are given as regular expressions. In that case, only the full recipient address is given to the regular-expression map.

## SECURITY

```

```

The virtual(8) delivery agent is not security sensitive, provided that the lookup tables with recipient user/group ID information are adequately protected. This program is not designed to run chrooted.

The virtual(8) delivery agent disallows regular expression substitution of $1 etc. in regular expression lookup tables, because that would open a security hole.

The virtual(8) delivery agent will silently ignore requests to use the proxymap(8) server. Instead it will open the table directly. Before Postfix version 2.2, the virtual delivery agent will terminate with a fatal error.

## STANDARDS

```
RFC 822 (ARPA Internet Text Messages)
```

## DIAGNOSTICS

Mail bounces when the recipient has no mailbox or when the recipient is over disk quota. In all other cases, mail for an existing recipient is deferred and a warning is logged.

Problems and transactions are logged to syslogd(8) or postlogd(8). Corrupted message files are marked so that the queue manager can move them to the corrupt queue afterwards.

Depending on the setting of the notify_classes parameter, the postmaster is notified of bounces and of other trouble.

## BUGS

This delivery agent supports address extensions in email addresses and in lookup table keys, but does not propagate address extension information to the result of table lookup.

Postfix should have lookup tables that can return multiple result attributes. In order to avoid the inconvenience of maintaining three tables, use an LDAP or MYSQL database.

## CONFIGURATION PARAMETERS

```

```

Changes to main.cf are picked up automatically, as virtual(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.

## MAILBOX DELIVERY CONTROLS

```

```

virtual_mailbox_base (empty)

A prefix that the virtual(8) delivery agent prepends to all pathname results from $virtual_mailbox_maps table lookups.

virtual_mailbox_maps (empty)

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

virtual_minimum_uid (500)

The minimum user ID value that the virtual(8) delivery agent accepts as a result from $virtual_uid_maps table lookup.

virtual_uid_maps (empty)

Lookup tables with the per-recipient user ID that the virtual(8) delivery agent uses while writing to the recipient's mailbox.

virtual_gid_maps (empty)

Lookup tables with the per-recipient group ID for virtual(8) mailbox delivery.

Available in Postfix version 2.0 and later:

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_transport (virtual)

The default mail delivery transport and next-hop destination for final delivery to domains listed with $virtual_mailbox_domains.

Available in Postfix version 2.5.3 and later:

strict_mailbox_ownership (yes)

Defer delivery when a mailbox file is not owned by its recipient.

## LOCKING CONTROLS

```

```

virtual_mailbox_lock (see 'postconf -d' output)

How to lock a UNIX-style virtual(8) mailbox before attempting delivery.

deliver_lock_attempts (20)

The maximal number of attempts to acquire an exclusive lock on a mailbox file or bounce(8) logfile.

deliver_lock_delay (1s)

The time between attempts to acquire an exclusive lock on a mailbox file or bounce(8) logfile.

stale_lock_time (500s)

The time after which a stale exclusive mailbox lockfile is removed.

## RESOURCE AND RATE CONTROLS

```

```

virtual_mailbox_limit (51200000)

The maximal size in bytes of an individual virtual(8) mailbox or maildir file, or zero (no limit).

Implemented in the qmgr(8) daemon:

virtual_destination_concurrency_limit ($default_destination_concurrency_limit)

The maximal number of parallel deliveries to the same destination via the virtual message delivery transport.

virtual_destination_recipient_limit ($default_destination_recipient_limit)

The maximal number of recipients per message for the virtual message delivery transport.

## 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.

delay_logging_resolution_limit (2)

The maximal number of digits after the decimal point when logging sub-second delay values.

ipc_timeout (3600s)

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

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.

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.

syslog_facility (mail)

The syslog facility of Postfix logging.

syslog_name (see 'postconf -d' output)

A prefix that is prepended to the process name in syslog records, so that, for example, "smtpd" becomes "prefix/smtpd".

Available in Postfix version 3.0 and later:

virtual_delivery_status_filter ($default_delivery_status_filter)

Optional filter for the virtual(8) delivery agent to change the delivery status code or explanatory text of successful or unsuccessful deliveries.

Available in Postfix version 3.3 and later:

enable_original_recipient (yes)

Enable support for the original recipient address after an address is rewritten to a different address (for example with aliasing or with canonical mapping).

service_name (read-only)

The master.cf service name of a Postfix daemon process.

Available in Postfix 3.5 and later:

info_log_address_format (external)

The email address form that will be used in non-debug logging (info, warning, etc.).

## SEE ALSO

```
qmgr(8), queue manager
bounce(8), delivery status reports
postconf(5), configuration parameters
postlogd(8), Postfix logging
syslogd(8), system logging
```

## README_FILES

```
Use "postconf readme_directory" or
"postconf html_directory" to locate this information.
VIRTUAL_README, domain hosting howto
```

## LICENSE

```

```

The Secure Mailer license must be distributed with this software.

## HISTORY

This delivery agent was originally based on the Postfix local delivery agent. Modifications mainly consisted of removing code that either was not applicable or that was not safe in this context: aliases, ~user/.forward files, delivery to "|command" or to /file/name.

The Delivered-To: message header appears in the qmail system by Daniel Bernstein.

The maildir structure appears in the qmail system by Daniel Bernstein.

## AUTHOR(S)

```
Wietse Venema
IBM T.J. Watson Research
P.O. Box 704
Yorktown Heights, NY 10598, USA
Wietse Venema
Google, Inc.
111 8th Avenue
New York, NY 10011, USA
Andrew McNamara
andrewm@connect.com.au
connect.com.au Pty. Ltd.
Level 3, 213 Miller St
North Sydney 2060, NSW, Australia
```


tlsmgr

package: postfix-tls

title: tlsmgr(8)

text:
# tlsmgr(8)

## NAME
tlsmgr - Postfix TLS session cache and PRNG manager

## SYNOPSIS

```
tlsmgr [generic Postfix daemon options]
```

## DESCRIPTION

The tlsmgr(8) manages the Postfix TLS session caches. It stores and retrieves cache entries on request by smtpd(8) and smtp(8) processes, and periodically removes entries that have expired.

The tlsmgr(8) also manages the PRNG (pseudo random number generator) pool. It answers queries by the smtpd(8) and smtp(8) processes to seed their internal PRNG pools.

The tlsmgr(8)'s PRNG pool is initially seeded from an external source (EGD, /dev/urandom, or regular file). It is updated at configurable pseudo-random intervals with data from the external source. It is updated periodically with data from TLS session cache entries and with the time of day, and is updated with the time of day whenever a process requests tlsmgr(8) service.

The tlsmgr(8) saves the PRNG state to an exchange file periodically and when the process terminates, and reads the exchange file when initializing its PRNG.

## SECURITY

```

```

The tlsmgr(8) is not security-sensitive. The code that maintains the external and internal PRNG pools does not "trust" the data that it manipulates, and the code that maintains the TLS session cache does not touch the contents of the cached entries, except for seeding its internal PRNG pool.

The tlsmgr(8) can be run chrooted and with reduced privileges. At process startup it connects to the entropy source and exchange file, and creates or truncates the optional TLS session cache files.

With Postfix version 2.5 and later, the tlsmgr(8) no longer uses root privileges when opening cache files. These files should now be stored under the Postfix-owned data_directory. As a migration aid, an attempt to open a cache file under a non-Postfix directory is redirected to the Postfix-owned data_directory, and a warning is logged.

## DIAGNOSTICS

Problems and transactions are logged to syslogd(8) or postlogd(8).

## BUGS

There is no automatic means to limit the number of entries in the TLS session caches and/or the size of the TLS cache files.

## CONFIGURATION PARAMETERS

```

```

Changes to main.cf are not picked up automatically, because tlsmgr(8) is a persistent processes. Use the command "postfix reload" after a configuration change.

The text below provides only a parameter summary. See postconf(5) for more details including examples.

## TLS SESSION CACHE

```

```

lmtp_tls_loglevel (0)

The LMTP-specific version of the smtp_tls_loglevel configuration parameter.

lmtp_tls_session_cache_database (empty)

The LMTP-specific version of the smtp_tls_session_cache_database configuration parameter.

lmtp_tls_session_cache_timeout (3600s)

The LMTP-specific version of the smtp_tls_session_cache_timeout configuration parameter.

smtp_tls_loglevel (0)

Enable additional Postfix SMTP client logging of TLS activity.

smtp_tls_session_cache_database (empty)

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

smtp_tls_session_cache_timeout (3600s)

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

smtpd_tls_loglevel (0)

Enable additional Postfix SMTP server logging of TLS activity.

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.

## PSEUDO RANDOM NUMBER GENERATOR

```

```

tls_random_source (see 'postconf -d' output)

The external entropy source for the in-memory tlsmgr(8) pseudo random number generator (PRNG) pool.

tls_random_bytes (32)

The number of bytes that tlsmgr(8) reads from $tls_random_source when (re)seeding the in-memory pseudo random number generator (PRNG) pool.

tls_random_exchange_name (see 'postconf -d' output)

Name of the pseudo random number generator (PRNG) state file that is maintained by tlsmgr(8).

tls_random_prng_update_period (3600s)

The time between attempts by tlsmgr(8) to save the state of the pseudo random number generator (PRNG) to the file specified with $tls_random_exchange_name.

tls_random_reseed_period (3600s)

The maximal time between attempts by tlsmgr(8) to re-seed the in-memory pseudo random number generator (PRNG) pool from external sources.

## MISCELLANEOUS CONTROLS

```

```

config_directory (see 'postconf -d' output)

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

data_directory (see 'postconf -d' output)

The directory with Postfix-writable data files (for example: caches, pseudo-random numbers).

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.

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.

syslog_facility (mail)

The syslog facility of Postfix logging.

syslog_name (see 'postconf -d' output)

A prefix that is prepended to the process name in syslog records, so that, for example, "smtpd" becomes "prefix/smtpd".

Available in Postfix 3.3 and later:

service_name (read-only)

The master.cf service name of a Postfix daemon process.

## SEE ALSO

```
smtp(8), Postfix SMTP client
smtpd(8), Postfix SMTP server
postconf(5), configuration parameters
master(5), generic daemon options
master(8), process manager
postlogd(8), Postfix logging
syslogd(8), system logging
```

## README FILES

```

```

Use "postconf readme_directory" or "postconf html_directory" to locate this information.

```
TLS_README, Postfix TLS configuration and operation
```

## LICENSE

```

```

The Secure Mailer license must be distributed with this software.

## HISTORY

This service was introduced with Postfix version 2.2.

## AUTHOR(S)

```
Lutz Jaenicke
BTU Cottbus
Allgemeine Elektrotechnik
Universitaetsplatz 3-4
D-03044 Cottbus, Germany
Adapted by:
Wietse Venema
IBM T.J. Watson Research
P.O. Box 704
Yorktown Heights, NY 10598, USA
Wietse Venema
Google, Inc.
111 8th Avenue
New York, NY 10011, USA
```