tcp_table - Postfix client/server table lookup protocol
postmap -q "string" tcp:host:port
postmap -q - tcp:host:port <inputfile
The Postfix mail system uses optional tables for address rewriting or mail routing. These
tables are usually in dbm or db format. Alternatively, table lookups can be directed to a
To find out what types of lookup tables your Postfix system supports use the "postconf -m"
To test lookup tables, use the "postmap -q" command as described in the SYNOPSIS above.
The TCP map class implements a very simple protocol: the client sends a request, and the
server sends one reply. Requests and replies are sent as one line of ASCII text, termi-
nated by the ASCII newline character. Request and reply parameters (see below) are sepa-
rated by whitespace.
Send and receive operations must complete in 100 seconds.
Each request specifies a command, a lookup key, and possibly a lookup result.
get SPACE key NEWLINE
Look up data under the specified key.
put SPACE key SPACE value NEWLINE
This request is currently not implemented.
Each reply specifies a status code and text. Replies must be no longer than 4096 charac-
ters including the newline terminator.
500 SPACE text NEWLINE
In case of a lookup request, the requested data does not exist. In case of an
update request, the request was rejected. The text describes the nature of the
400 SPACE text NEWLINE
This indicates an error condition. The text describes the nature of the problem.
The client should retry the request later.
200 SPACE text NEWLINE
The request was successful. In the case of a lookup request, the text contains an
encoded version of the requested data.
In request and reply parameters, the character %, each non-printing character, and each
whitespace character must be replaced by %XX, where XX is the corresponding ASCII hexadec-
imal character value. The hexadecimal codes can be specified in any case (upper, lower,
The Postfix client always encodes a request. The server may omit the encoding as long as
the reply is guaranteed to not contain the % or NEWLINE character.
Do not use TCP lookup tables for security critical purposes. The client-server connection
is not protected and the server is not authenticated.
Only the lookup method is currently implemented.
The client does not hang up when the connection is idle for a long time.
postmap(1), Postfix lookup table manager
regexp_table(5), format of regular expression tables
pcre_table(5), format of PCRE tables
cidr_table(5), format of CIDR tables
Use "postconf readme_directory" or "postconf html_directory" to locate this information.
DATABASE_README, Postfix lookup table overview
The Secure Mailer license must be distributed with this software.
IBM T.J. Watson Research
P.O. Box 704
Yorktown Heights, NY 10598, USA