smtpd - Postfix SMTP server
smtpd [generic Postfix daemon options]
sendmail -bs
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.
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.
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 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)
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.
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.
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
(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:
- 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.
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:
- Rewrite message header addresses in mail from these clients and update
incomplete addresses with the domain name in $myorigin or $mydomain;
either don't rewrite message headers from other clients at all, or rewrite
message headers and update incomplete addresses with the domain specified
in the remote_header_rewrite_domain parameter.
As of version 1.0, Postfix can be configured to send new mail to
an external content filter AFTER the mail is queued. This content filter is
expected to inject mail back into a (Postfix or other) MTA for further
delivery. See the FILTER_README document for details.
- content_filter
(empty)
- After the message is queued, send the entire message to the specified
transport:destination.
As of version 2.1, the Postfix SMTP server can be configured to
send incoming mail to a real-time SMTP-based content filter BEFORE mail is
queued. This content filter is expected to inject mail back into Postfix.
See the SMTPD_PROXY_README document for details on how to configure and
operate this feature.
- smtpd_proxy_filter
(empty)
- The hostname and TCP port of the mail filtering proxy server.
- smtpd_proxy_ehlo
($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.
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.
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.
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:
- 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 $smtpd_sasl_path.conf file.
Available in Postfix version 2.11 and later:
- smtpd_sasl_service
(smtp)
- The service name that is passed to the SASL plug-in that is selected with
smtpd_sasl_type and smtpd_sasl_path.
Detailed information about STARTTLS configuration may be found in
the TLS_README document.
- smtpd_tls_security_level
(empty)
- The SMTP TLS security level for the Postfix SMTP server; when a non-empty
value is specified, this overrides the obsolete parameters smtpd_use_tls
and smtpd_enforce_tls.
- smtpd_sasl_tls_security_options
($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
(!SSLv2, !SSLv3)
- The SSL/TLS protocols accepted by the Postfix SMTP server with mandatory
TLS encryption.
- Request that the Postfix SMTP server produces Received: message headers
that include information about the protocol and cipher used, as well as
the 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
(md5)
- 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
(!SSLv2, !SSLv3)
- List of TLS protocols that the Postfix SMTP server will exclude or include
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.
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.
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.
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.
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 $debug_peer_level.
- error_notice_recipient
(postmaster)
- The recipient of postmaster notifications about mail delivery problems
that are caused by policy, resource, software or protocol errors.
- internal_mail_filter_classes
(empty)
- What categories of Postfix-generated mail are subject to before-queue
content inspection by non_smtpd_milters, header_checks and
body_checks.
- notify_classes
(resource, software)
- The list of error classes that are reported to the postmaster.
- Optional information that is appended after each Postfix SMTP server 4XX
or 5XX response.
- soft_bounce
(no)
- Safety net to keep mail queued that would otherwise be returned to the
sender.
Available in Postfix version 2.1 and later:
- smtpd_authorized_xclient_hosts
(empty)
- What remote SMTP clients are allowed to use the XCLIENT feature.
Available in Postfix version 2.10 and later:
- smtpd_log_access_permit_actions
(empty)
- Enable logging of the named "permit" actions in SMTP server
access lists (by default, the SMTP server logs "reject" actions
but not "permit" actions).
As of Postfix version 2.0, the SMTP server rejects mail for
unknown recipients. This prevents the mail queue from clogging up with
undeliverable MAILER-DAEMON messages. Additional information on this topic
is in the LOCAL_RECIPIENT_README and ADDRESS_CLASS_README documents.
- show_user_unknown_table_name
(yes)
- Display the name of the recipient table in the "User unknown"
responses.
- canonical_maps
(empty)
- Optional address mapping lookup tables for message headers and
envelopes.
- recipient_canonical_maps
(empty)
- Optional address mapping lookup tables for envelope and header recipient
addresses.
- sender_canonical_maps
(empty)
- Optional address mapping lookup tables for envelope and header sender
addresses.
Parameters concerning known/unknown local recipients:
- mydestination
($myhostname, localhost.$mydomain, localhost)
- 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
(all)
- 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.
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.
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.
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 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.
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
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
The Secure Mailer license must be distributed with this
software.
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