redhat man page for regexp_table

REGEXP_TABLE(5) 						File Formats Manual						   REGEXP_TABLE(5)

NAME
       regexp_table - format of Postfix regular expression tables

SYNOPSIS
       regexp:/etc/postfix/filename

DESCRIPTION
       The  Postfix mail system uses optional tables for address rewriting or mail routing. These tables are usually in dbm or db format. Alterna-
       tively, lookup tables can be specified in POSIX regular expression form.

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

       The general form of a Postfix regular expression table is:

       pattern result
	      When pattern matches a search string, use the corresponding result.

       blank lines and comments
	      Empty lines and whitespace-only lines are ignored, as are lines whose first non-whitespace character is a `#'.

       multi-line text
	      A logical line starts with non-whitespace text. A line that starts with whitespace continues a logical line.

       pattern1!pattern2 result
	      Matches pattern1 but not pattern2.

       Each pattern is a regular expression enclosed by a pair of delimiters.  The regular expression syntax is described  in  re_format(7).   The
       expression  delimiter  can  be any character, except whitespace or characters that have special meaning (traditionally the forward slash is
       used). The regular expression can contain whitespace.

       By default, matching is case-insensitive, although following the second slash with an `i' flag will reverse this. Other flags are `x' (dis-
       able extended expression syntax), and `m' (enable multi-line mode).

       Each pattern is applied to the entire lookup key string.  Depending on the application, that string is an entire client hostname, an entire
       client IP address, or an entire mail address.  Thus, no parent domain or parent network search is done, and user@domain mail addresses  are
       not broken up into their user and domain constituent parts, nor is user+foo broken up into user and foo.

       Patterns are applied in the order as specified in the table, until a pattern is found that matches the search string.

       Substitution  of  substrings  from  the	matched expression into the result string is possible using $1, $2, etc.. The macros in the result
       string may need to be written as ${n} or $(n) if they aren't followed by whitespace.

EXAMPLE SMTPD ACCESS MAP
       # Disallow sender-specified routing. This is a must if you relay mail
       # for other domains.
       /[%!@].*[%!@]/	    550 Sender-specified routing rejected

       # Postmaster is OK, that way they can talk to us about how to fix
       # their problem.
       /^postmaster@/	    OK

       # Protect your outgoing majordomo exploders
       /^(.*)-outgoing@(.*)$/!/^owner-/ 	550 Use ${1}@${2} instead

EXAMPLE HEADER FILTER MAP
       # These were once common in junk mail.
       /^Subject: make money fast/     REJECT
       /^To: friend@public.com/       REJECT

SEE ALSO
       pcre_table(5) format of PCRE tables

AUTHOR(S)
       The regexp table lookup code was originally written by:
       LaMont Jones
       lamont@hp.com

       That code was based on the PCRE dictionary contributed by:
       Andrew McNamara
       andrewm@connect.com.au
       connect.com.au Pty. Ltd.
       Level 3, 213 Miller St
       North Sydney, NSW, Australia

       Adopted and adapted by:
       Wietse Venema
       IBM T.J. Watson Research
       P.O. Box 704
       Yorktown Heights, NY 10598, USA

																   REGEXP_TABLE(5)