SMTPD(8) SMTPD(8)
NAME
smtpd - Postfix SMTP server
SYNOPSIS
smtpd [generic Postfix daemon options]
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 configu-ration configuration
ration file.
SECURITY
The SMTP server is moderately security-sensitive. It talks to SMTP clients and to DNS servers on the
network. The SMTP server can be run chrooted at fixed low privilege.
STANDARDS
RFC 821 (SMTP protocol)
RFC 1123 (Host requirements)
RFC 1652 (8bit-MIME transport)
RFC 1869 (SMTP service extensions)
RFC 1870 (Message Size Declaration)
RFC 1985 (ETRN command)
RFC 2034 (SMTP Enhanced Error Codes)
RFC 2554 (AUTH command)
RFC 2821 (SMTP protocol)
RFC 2920 (SMTP Pipelining)
RFC 3207 (STARTTLS command)
RFC 3461 (SMTP DSN Extension)
RFC 3463 (Enhanced Status Codes)
DIAGNOSTICS
Problems and transactions are logged to syslogd(8).
Depending on the setting of the notify_classes parameter, the postmaster is notified of bounces, pro-tocol protocol
tocol problems, policy violations, and of other trouble.
CONFIGURATION PARAMETERS
Changes to main.cf are picked up automatically, as smtpd(8) processes run for only a limited amount
of time. Use the command "postfix reload" to speed up a change.
The text below provides only a parameter summary. See postconf(5) for more details including exam-ples. examples.
ples.
COMPATIBILITY CONTROLS
The following parameters work around implementation errors in other software, and/or allow you to
override standards in order to prevent undesirable use.
broken_sasl_auth_clients (no)
Enable inter-operability with SMTP clients that implement an obsolete version of the AUTH com-mand command
mand (RFC 2554).
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 syn-tax syntax
tax checks and without changing state.
strict_rfc821_envelopes (no)
Require that addresses received in SMTP MAIL FROM and RCPT TO commands are enclosed with <>,
and that those addresses do not contain RFC 822 style comments or phrases.
Available in Postfix version 2.1 and later:
resolve_null_domain (no)
Resolve an address that ends in the "@" null domain as if the local hostname were specified,
instead of rejecting the address as invalid.
smtpd_reject_unlisted_sender (no)
Request that the Postfix SMTP server rejects mail from unknown sender addresses, even when no
explicit reject_unlisted_sender access restriction is specified.
smtpd_sasl_exceptions_networks (empty)
What SMTP clients Postfix will not offer AUTH support to.
Available in Postfix version 2.2 and later:
smtpd_discard_ehlo_keyword_address_maps (empty)
Lookup tables, indexed by the remote SMTP client address, with case insensitive lists of EHLO
keywords (pipelining, starttls, auth, etc.) that the SMTP server will not send in the EHLO
response to a remote SMTP client.
smtpd_discard_ehlo_keywords (empty)
A case insensitive list of EHLO keywords (pipelining, starttls, auth, etc.) that the SMTP
server will not send in the EHLO response to a remote SMTP client.
smtpd_delay_open_until_valid_rcpt (yes)
Postpone the start of an SMTP mail transaction until a valid RCPT TO command is received.
Available in Postfix version 2.3 and later:
smtpd_tls_always_issue_session_ids (yes)
Force the Postfix SMTP server to issue a TLS session id, even when TLS session caching is
turned off (smtpd_tls_session_cache_database is empty).
ADDRESS REWRITING CONTROLS
See the ADDRESS_REWRITING_README document for a detailed discussion of Postfix address rewriting.
receive_override_options (empty)
Enable or disable recipient validation, built-in content filtering, or address mapping.
Available in Postfix version 2.2 and later:
local_header_rewrite_clients (permit_inet_interfaces)
Rewrite message header addresses in mail from these clients and update incomplete addresses
with the domain name in $myorigin or $mydomain; either don't rewrite message headers from
other clients at all, or rewrite message headers and update incomplete addresses with the
domain specified in the remote_header_rewrite_domain parameter.
AFTER QUEUE EXTERNAL CONTENT INSPECTION CONTROLS
As of version 1.0, Postfix can be configured to send new mail to an external content filter AFTER the
mail is queued. This content filter is expected to inject mail back into a (Postfix or other) MTA for
further delivery. See the FILTER_README document for details.
content_filter (empty)
The name of a mail delivery transport that filters mail after it is queued.
BEFORE QUEUE EXTERNAL CONTENT INSPECTION CONTROLS
As of version 2.1, the Postfix SMTP server can be configured to send incoming mail to a real-time
SMTP-based content filter BEFORE mail is queued. This content filter is expected to inject mail back
into Postfix. See the SMTPD_PROXY_README document for details on how to configure and operate this
feature.
smtpd_proxy_filter (empty)
The hostname and TCP port of the mail filtering proxy server.
smtpd_proxy_ehlo ($myhostname)
How the Postfix SMTP server announces itself to the proxy filter.
smtpd_proxy_timeout (100s)
The time limit for connecting to a proxy filter and for sending or receiving information.
BEFORE QUEUE MILTER CONTROLS
As of version 2.3, Postfix supports the Sendmail version 8 Milter (mail filter) protocol. These con-tent content
tent 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 (2)
The mail filter protocol version and optional protocol extensions for communication with a
Milter (mail filter) application.
milter_default_action (tempfail)
The default action when a Milter (mail filter) application is unavailable or mis-configured.
milter_macro_daemon_name ($myhostname)
The {daemon_name} macro value for Milter (mail filter) applications.
milter_macro_v ($mail_name $mail_version)
The {v} macro value for Milter (mail filter) applications.
milter_connect_timeout (30s)
The time limit for connecting to a Milter (mail filter) application, and for negotiating pro-tocol protocol
tocol 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 -n output)
The macros that are sent to Milter (mail filter) applications after completion of an SMTP con-nection. connection.
nection.
milter_helo_macros (see postconf -n output)
The macros that are sent to Milter (mail filter) applications after the SMTP HELO or EHLO com-mand. command.
mand.
milter_mail_macros (see postconf -n output)
The macros that are sent to Milter (mail filter) applications after the SMTP MAIL FROM com-mand. command.
mand.
milter_rcpt_macros (see postconf -n output)
The macros that are sent to Milter (mail filter) applications after the SMTP RCPT TO command.
milter_data_macros (see postconf -n 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 -n output)
The macros that are sent to version 3 or higher Milter (mail filter) applications after an
unknown SMTP command.
milter_end_of_data_macros (see postconf -n output)
The macros that are sent to Milter (mail filter) applications after the message end-of-data.
GENERAL CONTENT INSPECTION CONTROLS
The following parameters are applicable for both built-in and external content filters.
Available in Postfix version 2.1 and later:
receive_override_options (empty)
Enable or disable recipient validation, built-in content filtering, or address mapping.
EXTERNAL CONTENT INSPECTION CONTROLS
The following parameters are applicable for both before-queue and after-queue content filtering.
Available in Postfix version 2.1 and later:
smtpd_authorized_xforward_hosts (empty)
What SMTP clients are allowed to use the XFORWARD feature.
SASL AUTHENTICATION CONTROLS
Postfix SASL support (RFC 2554) can be used to authenticate remote SMTP clients to the Postfix SMTP
server, and to authenticate the Postfix SMTP client to a remote SMTP server. See the SASL_README
document for details.
broken_sasl_auth_clients (no)
Enable inter-operability with SMTP clients that implement an obsolete version of the AUTH com-mand command
mand (RFC 2554).
smtpd_sasl_auth_enable (no)
Enable SASL authentication in the Postfix SMTP server.
smtpd_sasl_local_domain (empty)
The name of the local SASL authentication realm.
smtpd_sasl_security_options (noanonymous)
SASL security options; as of Postfix 2.3 the list of available features depends on the SASL
server implementation that is selected with smtpd_sasl_type.
smtpd_sender_login_maps (empty)
Optional lookup table with the SASL login names that own sender (MAIL FROM) addresses.
Available in Postfix version 2.1 and later:
smtpd_sasl_exceptions_networks (empty)
What SMTP clients Postfix will not offer AUTH support to.
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 is passed 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.
STARTTLS SUPPORT CONTROLS
Detailed information about STARTTLS configuration may be found in the TLS_README document.
smtpd_tls_security_level (empty)
The SMTP TLS security level for the Postfix SMTP server; when a non-empty value is specified,
this overrides the obsolete parameters smtpd_use_tls and smtpd_enforce_tls.
smtpd_sasl_tls_security_options ($smtpd_sasl_security_options)
The SASL authentication security options that the Postfix SMTP server uses for TLS encrypted
SMTP sessions.
smtpd_starttls_timeout (300s)
The time limit for Postfix SMTP server write and read operations during TLS startup and shut-down shutdown
down handshake procedures.
smtpd_tls_CAfile (empty)
The file with the certificate of the certification authority (CA) that issued the Postfix SMTP
server certificate.
smtpd_tls_CAfile (empty)
The file with the certificate of the certification authority (CA) that issued the Postfix SMTP
server certificate.
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 (5)
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 secu-rity security
rity levels.
smtpd_tls_dcert_file (empty)
File with the Postfix SMTP server DSA certificate in PEM format.
smtpd_tls_dh1024_param_file (empty)
File with DH parameters that the Postfix SMTP server should use with EDH ciphers.
smtpd_tls_dh512_param_file (empty)
File with DH parameters that the Postfix SMTP server should use with EDH ciphers.
smtpd_tls_dkey_file ($smtpd_tls_dcert_file)
File with the Postfix SMTP server DSA private key in PEM format.
smtpd_tls_key_file ($smtpd_tls_cert_file)
File with the Postfix SMTP server RSA private key in PEM format.
smtpd_tls_loglevel (0)
Enable additional Postfix SMTP server logging of TLS activity.
smtpd_tls_mandatory_ciphers (medium)
The minimum TLS cipher grade that the Postfix SMTP server will use with mandatory TLS encryp-tion. encryption.
tion.
smtpd_tls_mandatory_exclude_ciphers (empty)
Additional list of ciphers or cipher types to exclude from the SMTP server cipher list at
mandatory TLS security levels.
smtpd_tls_mandatory_protocols (SSLv3, TLSv1)
The 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 informa-tion information
tion about the protocol and cipher used, as well as the client CommonName and client certifi-cate certificate
cate issuer CommonName.
smtpd_tls_req_ccert (no)
With mandatory TLS encryption, require a remote SMTP client certificate in order to allow TLS
connections to proceed.
smtpd_tls_session_cache_database (empty)
Name of the file containing the optional Postfix SMTP server TLS session cache.
smtpd_tls_session_cache_timeout (3600s)
The expiration time of Postfix SMTP server TLS session cache information.
smtpd_tls_wrappermode (no)
Run the Postfix SMTP server in the non-standard "wrapper" mode, instead of using the STARTTLS
command.
tls_daemon_random_bytes (32)
The number of pseudo-random bytes that an smtp(8) or smtpd(8) process requests from the
tlsmgr(8) server in order to seed its internal pseudo random number generator (PRNG).
tls_high_cipherlist (ALL:!EXPORT:!LOW:!MEDIUM:+RC4:@STRENGTH)
The OpenSSL cipherlist for "HIGH" grade ciphers.
tls_medium_cipherlist (ALL:!EXPORT:!LOW:+RC4:@STRENGTH)
The OpenSSL cipherlist for "MEDIUM" or higher grade ciphers.
tls_low_cipherlist (ALL:!EXPORT:+RC4:@STRENGTH)
The OpenSSL cipherlist for "LOW" or higher grade ciphers.
tls_export_cipherlist (ALL:+RC4:@STRENGTH)
The OpenSSL cipherlist for "EXPORT" or higher grade ciphers.
tls_null_cipherlist (eNULL:!aNULL)
The OpenSSL cipherlist for "NULL" grade ciphers that provide authentication without encryp-tion. encryption.
tion.
OBSOLETE STARTTLS CONTROLS
The following configuration parameters exist for compatibility with Postfix versions before 2.3. Sup-port Support
port for these will be removed in a future release.
smtpd_use_tls (no)
Opportunistic TLS: announce STARTTLS support to SMTP clients, but do not require that clients
use TLS encryption.
smtpd_enforce_tls (no)
Mandatory TLS: announce STARTTLS support to SMTP clients, and require that clients use TLS
encryption.
smtpd_tls_cipherlist (empty)
Obsolete Postfix < 2.3 control for the Postfix SMTP server TLS cipher list.
VERP SUPPORT CONTROLS
With VERP style delivery, each recipient of a message receives a customized copy of the message with
his/her own recipient address encoded in the envelope sender address. The VERP_README file describes
configuration and operation details of Postfix support for variable envelope return path addresses.
VERP style delivery is requested with the SMTP XVERP command or with the "sendmail -V" command-line
option and is available in Postfix version 1.1 and later.
default_verp_delimiters (+=)
The two default VERP delimiter characters.
verp_delimiter_filter (-=+)
The characters Postfix accepts as VERP delimiter characters on the Postfix sendmail(1) command
line and in SMTP commands.
Available in Postfix version 1.1 and 2.0:
authorized_verp_clients ($mynetworks)
What SMTP clients are allowed to specify the XVERP command.
Available in Postfix version 2.1 and later:
smtpd_authorized_verp_clients ($authorized_verp_clients)
What SMTP clients are allowed to specify the XVERP command.
TROUBLE SHOOTING CONTROLS
The DEBUG_README document describes how to debug parts of the Postfix mail system. The methods vary
from making the software log a lot of detail, to running some daemon processes under control of a
call tracer or debugger.
debug_peer_level (2)
The increment in verbose logging level when a remote client or server matches a pattern in the
debug_peer_list parameter.
debug_peer_list (empty)
Optional list of remote client or server hostname or network address patterns that cause the
verbose logging level to increase by the amount specified in $debug_peer_level.
error_notice_recipient (postmaster)
The recipient of postmaster notifications about mail delivery problems that are caused by pol-
icy, resource, software or protocol errors.
internal_mail_filter_classes (empty)
What categories of Postfix-generated mail are subject to before-queue content inspection by
non_smtpd_milters, header_checks and body_checks.
notify_classes (resource, software)
The list of error classes that are reported to the postmaster.
soft_bounce (no)
Safety net to keep mail queued that would otherwise be returned to the sender.
Available in Postfix version 2.1 and later:
smtpd_authorized_xclient_hosts (empty)
What SMTP clients are allowed to use the XCLIENT feature.
KNOWN VERSUS UNKNOWN RECIPIENT CONTROLS
As of Postfix version 2.0, the SMTP server rejects mail for unknown recipients. This prevents the
mail queue from clogging up with undeliverable MAILER-DAEMON messages. Additional information on this
topic is in the LOCAL_RECIPIENT_README and ADDRESS_CLASS_README documents.
show_user_unknown_table_name (yes)
Display the name of the recipient table in the "User unknown" responses.
canonical_maps (empty)
Optional address mapping lookup tables for message headers and envelopes.
recipient_canonical_maps (empty)
Optional address mapping lookup tables for envelope and header recipient addresses.
Parameters concerning known/unknown local recipients:
mydestination ($myhostname, localhost.$mydomain, localhost)
The list of domains that are delivered via the $local_transport mail delivery transport.
inet_interfaces (all)
The network interface addresses that this mail system receives mail on.
proxy_interfaces (empty)
The network interface addresses that this mail system receives mail on by way of a proxy or
network address translation unit.
inet_protocols (ipv4)
The Internet protocols Postfix will attempt to use when making or accepting connections.
local_recipient_maps (proxy:unix:passwd.byname $alias_maps)
Lookup tables with all names or addresses of local recipients: a recipient address is local
when its domain matches $mydestination, $inet_interfaces or $proxy_interfaces.
unknown_local_recipient_reject_code (550)
The numerical Postfix SMTP server response code when a recipient address is local, and
$local_recipient_maps specifies a list of lookup tables that does not match the recipient.
Parameters concerning known/unknown recipients of relay destinations:
relay_domains ($mydestination)
What destination domains (and subdomains thereof) this system will relay mail to.
relay_recipient_maps (empty)
Optional lookup tables with all valid addresses in the domains that match $relay_domains.
unknown_relay_recipient_reject_code (550)
The numerical Postfix SMTP server reply code when a recipient address matches $relay_domains,
and relay_recipient_maps specifies a list of lookup tables that does not match the recipient
address.
Parameters concerning known/unknown recipients in virtual alias domains:
virtual_alias_domains ($virtual_alias_maps)
Postfix is final destination for the specified list of virtual alias domains, that is, domains
for which all addresses are aliased to addresses in other local or remote domains.
virtual_alias_maps ($virtual_maps)
Optional lookup tables that alias specific mail addresses or domains to other local or remote
address.
unknown_virtual_alias_reject_code (550)
The SMTP server reply code when a recipient address matches $virtual_alias_domains, and $vir-tual_alias_maps $virtual_alias_maps
tual_alias_maps specifies a list of lookup tables that does not match the recipient address.
Parameters concerning known/unknown recipients in virtual mailbox domains:
virtual_mailbox_domains ($virtual_mailbox_maps)
Postfix is final destination for the specified list of domains; mail is delivered via the
$virtual_transport mail delivery transport.
virtual_mailbox_maps (empty)
Optional lookup tables with all valid addresses in the domains that match $virtual_mail-box_domains. $virtual_mailbox_domains.
box_domains.
unknown_virtual_mailbox_reject_code (550)
The SMTP server reply code when a recipient address matches $virtual_mailbox_domains, and
$virtual_mailbox_maps specifies a list of lookup tables that does not match the recipient
address.
RESOURCE AND RATE CONTROLS
The following parameters limit resource usage by the SMTP server and/or control client request rates.
line_length_limit (2048)
Upon input, long lines are chopped up into pieces of at most this length; upon delivery, long
lines are reconstructed.
queue_minfree (0)
The minimal amount of free space in bytes in the queue file system that is needed to receive
mail.
message_size_limit (10240000)
The maximal size in bytes of a message, including envelope information.
smtpd_recipient_limit (1000)
The maximal number of recipients that the Postfix SMTP server accepts per message delivery
request.
smtpd_timeout (300s)
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 connection count, connection rate, or SMTP request rate
restrictions.
Available in Postfix version 2.3 and later:
smtpd_client_new_tls_session_rate_limit (0)
The maximal number of new (i.e., uncached) TLS sessions that a remote SMTP client is allowed
to negotiate with this service per time unit.
TARPIT CONTROLS
When a remote SMTP client makes errors, the Postfix SMTP server can insert delays before responding.
This can help to slow down run-away software. The behavior is controlled by an error counter that
counts the number of errors within an SMTP session that a client makes without delivering mail.
smtpd_error_sleep_time (1s)
With Postfix version 2.1 and later: the SMTP server response delay after a client has made
more than $smtpd_soft_error_limit errors, and fewer than $smtpd_hard_error_limit errors, with-out without
out 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 (20)
The maximal number of errors a remote SMTP client is allowed to make without delivering mail.
smtpd_junk_command_limit (100)
The number of junk commands (NOOP, VRFY, ETRN or RSET) that a remote SMTP client can send
before the Postfix SMTP server starts to increment the error counter with each junk command.
Available in Postfix version 2.1 and later:
smtpd_recipient_overshoot_limit (1000)
The number of recipients that a remote SMTP client can send in excess of the limit specified
with $smtpd_recipient_limit, before the Postfix SMTP server increments the per-session error
count for each excess recipient.
ACCESS POLICY DELEGATION CONTROLS
As of version 2.1, Postfix can be configured to delegate access policy decisions to an external
server that runs outside Postfix. See the file SMTPD_POLICY_README for more information.
smtpd_policy_service_max_idle (300s)
The time after which an idle SMTPD policy service connection is closed.
smtpd_policy_service_max_ttl (1000s)
The time after which an active SMTPD policy service connection is closed.
smtpd_policy_service_timeout (100s)
The time limit for connecting to, writing to or receiving from a delegated SMTPD policy
server.
ACCESS CONTROLS
The SMTPD_ACCESS_README document gives an introduction to all the SMTP server access control fea-tures. features.
tures.
smtpd_delay_reject (yes)
Wait until the RCPT TO command before evaluating $smtpd_client_restrictions,
$smtpd_helo_restrictions and $smtpd_sender_restrictions, or wait until the ETRN command before
evaluating $smtpd_client_restrictions and $smtpd_helo_restrictions.
parent_domain_matches_subdomains (see 'postconf -d' output)
What Postfix features match subdomains of "domain.tld" automatically, instead of requiring an
explicit ".domain.tld" pattern.
smtpd_client_restrictions (empty)
Optional SMTP server access restrictions in the context of a client SMTP connection request.
smtpd_helo_required (no)
Require that a remote SMTP client introduces itself at the beginning of an SMTP session with
the HELO or EHLO command.
smtpd_helo_restrictions (empty)
Optional restrictions that the Postfix SMTP server applies in the context of the SMTP HELO
command.
smtpd_sender_restrictions (empty)
Optional restrictions that the Postfix SMTP server applies in the context of the MAIL FROM
command.
smtpd_recipient_restrictions (permit_mynetworks, reject_unauth_destination)
The access restrictions that the Postfix SMTP server applies in the context of the RCPT TO
command.
smtpd_etrn_restrictions (empty)
Optional SMTP server access restrictions in the context of a client ETRN request.
allow_untrusted_routing (no)
Forward mail with sender-specified routing (user[@%!]remote[@%!]site) from untrusted clients
to destinations matching $relay_domains.
smtpd_restriction_classes (empty)
User-defined aliases for groups of access restrictions.
smtpd_null_access_lookup_key (<>)
The lookup key to be used in SMTP access(5) tables instead of the null sender address.
permit_mx_backup_networks (empty)
Restrict the use of the permit_mx_backup SMTP access feature to only domains whose primary MX
hosts match the listed networks.
Available in Postfix version 2.0 and later:
smtpd_data_restrictions (empty)
Optional access restrictions that the Postfix SMTP server applies in the context of the SMTP
DATA command.
smtpd_expansion_filter (see 'postconf -d' output)
What characters are allowed in $name expansions of RBL reply templates.
Available in Postfix version 2.1 and later:
smtpd_reject_unlisted_sender (no)
Request that the Postfix SMTP server rejects mail from unknown sender addresses, even when no
explicit reject_unlisted_sender access restriction is specified.
smtpd_reject_unlisted_recipient (yes)
Request that the Postfix SMTP server rejects mail for unknown recipient addresses, even when
no explicit reject_unlisted_recipient access restriction is specified.
Available in Postfix version 2.2 and later:
smtpd_end_of_data_restrictions (empty)
Optional access restrictions that the Postfix SMTP server applies in the context of the SMTP
END-OF-DATA command.
SENDER AND RECIPIENT ADDRESS VERIFICATION CONTROLS
Postfix version 2.1 introduces sender and recipient address verification. This feature is imple-mented implemented
mented 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 (3)
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 (postmaster)
The sender address to use in address verification probes.
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.
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 when a client is rejected by an access(5) map
restriction.
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_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 restric-tion. restriction.
tion.
plaintext_reject_code (450)
The numerical Postfix SMTP server response code when a request is rejected by the
reject_plaintext_session restriction.
reject_code (554)
The numerical Postfix SMTP server response code when a remote SMTP client request is rejected
by the "reject" restriction.
relay_domains_reject_code (554)
The numerical Postfix SMTP server response code when a client request is rejected by the
reject_unauth_destination recipient restriction.
unknown_address_reject_code (450)
The numerical Postfix SMTP server response code when a sender or recipient address is rejected
by the reject_unknown_sender_domain or reject_unknown_recipient_domain restriction.
unknown_client_reject_code (450)
The numerical Postfix SMTP server response code when a client without valid address <=> name
mapping is rejected by the reject_unknown_client_hostname restriction.
unknown_hostname_reject_code (450)
The numerical Postfix SMTP server response code when the hostname specified with the HELO or
EHLO command is rejected by the reject_unknown_helo_hostname restriction.
Available in Postfix version 2.0 and later:
default_rbl_reply (see 'postconf -d' output)
The default SMTP server response template for a request that is rejected by an RBL-based
restriction.
multi_recipient_bounce_reject_code (550)
The numerical Postfix SMTP server response code when a remote SMTP client request is blocked
by the reject_multi_recipient_bounce restriction.
rbl_reply_maps (empty)
Optional lookup tables with RBL response templates.
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 connec-tion connection
tion before terminating voluntarily.
max_use (100)
The maximal number of incoming connections that a Postfix daemon process will service before
terminating voluntarily.
myhostname (see 'postconf -d' output)
The internet hostname of this mail system.
mynetworks (see 'postconf -d' output)
The list of "trusted" SMTP clients that have more privileges than "strangers".
myorigin ($myhostname)
The domain name that locally-posted mail appears to come from, and that locally posted mail is
delivered to.
process_id (read-only)
The process ID of a Postfix command or daemon process.
process_name (read-only)
The process name of a Postfix command or daemon process.
queue_directory (see 'postconf -d' output)
The location of the Postfix top-level queue directory.
recipient_delimiter (empty)
The separator between user names and address extensions (user+foo).
smtpd_banner ($myhostname ESMTP $mail_name)
The text that follows the 220 status code in the SMTP greeting banner.
syslog_facility (mail)
The syslog facility of Postfix logging.
syslog_name (postfix)
The mail system name that is prepended to the process name in syslog records, so that "smtpd"
becomes, for example, "postfix/smtpd".
Available in Postfix version 2.2 and later:
smtpd_forbidden_commands (CONNECT, GET, POST)
List of commands that causes the Postfix SMTP server to immediately terminate the session with
a 221 code.
SEE ALSO
anvil(8), connection/rate limiting
cleanup(8), message canonicalization
tlsmgr(8), TLS session and PRNG management
trivial-rewrite(8), address resolver
verify(8), address verification service
postconf(5), configuration parameters
master(5), generic daemon options
master(8), process manager
syslogd(8), system logging
README FILES
Use "postconf readme_directory" or "postconf html_directory" to locate this information.
ADDRESS_CLASS_README, blocking unknown hosted or relay recipients
ADDRESS_REWRITING_README Postfix address manipulation
FILTER_README, external after-queue content filter
LOCAL_RECIPIENT_README, blocking unknown local recipients
MILTER_README, before-queue mail filter applications
SMTPD_ACCESS_README, built-in access policies
SMTPD_POLICY_README, external policy server
SMTPD_PROXY_README, external before-queue content filter
SASL_README, Postfix SASL howto
TLS_README, Postfix STARTTLS howto
VERP_README, Postfix XVERP extension
XCLIENT_README, Postfix XCLIENT extension
XFORWARD_README, Postfix XFORWARD extension
LICENSE
The Secure Mailer license must be distributed with this software.
AUTHOR(S)
Wietse Venema
IBM T.J. Watson Research
P.O. Box 704
Yorktown Heights, NY 10598, USA
SASL support originally by:
Till Franke
SuSE Rhein/Main AG
65760 Eschborn, Germany
TLS support originally by:
Lutz Jaenicke
BTU Cottbus
Allgemeine Elektrotechnik
Universitaetsplatz 3-4
D-03044 Cottbus, Germany
SMTPD(8)
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