qmqpd man page

qmqpd — Postfix QMQP server


qmqpd [generic Postfix daemon options]


The Postfix QMQP server receives one message per connection. Each message is piped through the cleanup(8) daemon, and is placed into the incoming queue as one single queue file. The program expects to be run from the master(8) process manager.

The QMQP server implements one access policy: only explicitly authorized client hosts are allowed to use the service.


The QMQP server is moderately security-sensitive. It talks to QMQP clients and to DNS servers on the network. The QMQP server can be run chrooted at fixed low privilege.


Problems and transactions are logged to syslogd(8).


The QMQP protocol provides only one server reply per message delivery. It is therefore not possible to reject individual recipients.

The QMQP protocol requires the server to receive the entire message before replying. If a message is malformed, or if any netstring component is longer than acceptable, Postfix replies immediately and closes the connection. It is left up to the client to handle the situation.

Configuration Parameters

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

Content Inspection Controls

content_filter (empty)
After the message is queued, send the entire message to the specified transport:destination.
receive_override_options (empty)
Enable or disable recipient validation, built-in content filtering, or address mapping.

Smtputf8 Controls

Preliminary SMTPUTF8 support is introduced with Postfix 3.0.

smtputf8_enable (yes)
Enable preliminary SMTPUTF8 support for the protocols described in RFC 6531..6533.
smtputf8_autodetect_classes (sendmail, verify)
Detect that a message requires SMTPUTF8 support for the specified mail origin classes.

Resource and Rate Controls

line_length_limit (2048)
Upon input, long lines are chopped up into pieces of at most this length; upon delivery, long lines are reconstructed.
hopcount_limit (50)
The maximal number of Received: message headers that is allowed in the primary message headers.
message_size_limit (10240000)
The maximal size in bytes of a message, including envelope information.
qmqpd_timeout (300s)
The time limit for sending or receiving information over the network.

Trouble Shooting Controls

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.
soft_bounce (no)
Safety net to keep mail queued that would otherwise be returned to the sender.

Tarpit Controls

qmqpd_error_delay (1s)
How long the Postfix QMQP server will pause before sending a negative reply to the remote QMQP client.

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.
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.
qmqpd_authorized_clients (empty)
What remote QMQP clients are allowed to connect to the Postfix QMQP server port.
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)
The mail system name that is prepended to the process name in syslog records, so that "smtpd" becomes, for example, "postfix/smtpd".
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 2.5 and later:

qmqpd_client_port_logging (no)
Enable logging of the remote QMQP client port in addition to the hostname and IP address.

See Also

http://cr.yp.to/proto/qmqp.html, QMQP protocol
cleanup(8), message canonicalization
master(8), process manager
syslogd(8), system logging

Readme Files

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

QMQP_README, Postfix ezmlm-idx howto.


The Secure Mailer license must be distributed with this software.


The qmqpd service was introduced with Postfix version 1.1.


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

Referenced By

postconf(5), postfix(1).

Explore man page connections for qmqpd(8).