proxymap - Postfix lookup table proxy server
proxymap [generic Postfix daemon options]
The proxymap(8) server provides read-only table lookup
service to Postfix processes. The purpose of the service
o To overcome chroot restrictions. For example, a
chrooted SMTP server needs access to the system
passwd file in order to reject mail for non-exis-
tent local addresses, but it is not practical to
maintain a copy of the passwd file in the chroot
jail. The solution:
o To consolidate the number of open lookup tables by
sharing one open table among multiple processes.
For example, making mysql connections from every
Postfix daemon process results in "too many connec-
tions" errors. The solution:
The total number of connections is limited by the
number of proxymap server processes.
The proxymap(8) server implements the following requests:
open maptype:mapname flags
Open the table with type maptype and name mapname,
as controlled by flags. The reply includes the map-
type dependent flags (to distinguish a fixed string
table from a regular expression table).
lookup maptype:mapname flags key
Look up the data stored under the requested key.
The reply is the request completion status code
(below) and the lookup result value. The map-
type:mapname and flags are the same as with the
There is no close command, nor are tables implicitly
closed when a client disconnects. The purpose is to share
tables among multiple client processes.
SERVER PROCESS MANAGEMENT
proxymap(8) servers run under control by the Postfix mas-
ter(8) server. Each server can handle multiple simultane-
ous connections. When all servers are busy while a client
connects, the master(8) creates a new proxymap(8) server
process, provided that the process limit is not exceeded.
Each server terminates after serving at least $max_use
clients or after $max_idle seconds of idle time.
The proxymap(8) server opens only tables that are approved
via the proxy_read_maps configuration parameter, does not
talk to users, and can run at fixed low privilege,
chrooted or not. However, running the proxymap server
chrooted severely limits usability, because it can open
only chrooted tables.
The proxymap(8) server is not a trusted daemon process,
and must not be used to look up sensitive information such
as user or group IDs, mailbox file/directory names or
In Postfix version 2.2 and later, the proxymap client rec-
ognizes requests to access a table for security-sensitive
purposes, and opens the table directly. This allows the
same main.cf setting to be used by sensitive and non-sen-
Problems and transactions are logged to syslogd(8).
The proxymap(8) server provides service to multiple
clients, and must therefore not be used for tables that
have high-latency lookups.
On busy mail systems a long time may pass before prox-
ymap(8) relevant changes to main.cf are 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.
config_directory (see 'postconf -d' output)
The default location of the Postfix main.cf and
master.cf configuration files.
How much time a Postfix daemon process may take to
handle a request before it is terminated by a
built-in watchdog timer.
The time limit for sending or receiving information
over an internal communication channel.
The maximum amount of time that an idle Postfix
daemon process waits for the next service request
The maximal number of connection requests before a
Postfix daemon process terminates.
The process ID of a Postfix command or daemon
The process name of a Postfix command or daemon
proxy_read_maps (see 'postconf -d' output)
The lookup tables that the proxymap(8) server is
allowed to access.
postconf(5), configuration parameters
master(5), generic daemon options
DATABASE_README, Postfix lookup table overview
The Secure Mailer license must be distributed with this
The proxymap service was introduced with Postfix 2.0.
IBM T.J. Watson Research
P.O. Box 704
Yorktown Heights, NY 10598, USA