DOKK / manpages / debian 12 / postfix / tcp_table.5.en
TCP_TABLE(5) File Formats Manual TCP_TABLE(5)

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 TCP server.

To find out what types of lookup tables your Postfix system supports use the "postconf -m" command.

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, terminated by the ASCII newline character.
    Request and reply parameters (see below) are separated by whitespace.


Send and receive operations must complete in 100 seconds.










The tcp_table protocol supports only the lookup request. The
    request has the following form:



  

  
Look up data under the specified key.




Postfix will not generate partial search keys such as domain names
    without one or more subdomains, network addresses without one or more
    least-significant octets, or email addresses without the localpart, address
    extension or domain portion. This behavior is also found with cidr:, pcre:,
    and regexp: tables.










Each reply specifies a status code and text. Replies must be no
    longer than 4096 characters including the newline terminator.



  
500 SPACE text NEWLINE

  
In case of a lookup request, the requested data does not exist. The text
      describes the nature of the problem.

  
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 hexadecimal character value. The
    hexadecimal codes can be specified in any case (upper, lower, mixed).


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.








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