    REGEXP_TABLE(5)                                   REGEXP_TABLE(5)

    NAME
           regexp_table - format of Postfix regular expression tables

    SYNOPSIS
           regexp:/etc/postfix/filename

           postmap -q "string" regexp:/etc/postfix/filename

           postmap -q - regexp:/etc/postfix/filename <inputfile

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

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

           To  test  lookup  tables,  use  the  postmap  command   as
           described in the SYNOPSIS above.

           The general form of a Postfix regular expression table is:

           /pattern/flags result

           !/pattern/flags result
                  When pattern matches  (does  not  match)  a  search
                  string, use the corresponding result value.

           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  logi-
                  cal line.

           if /pattern/flags

           if !/pattern/flags

           endif  Match   the  search  string  against  the  patterns
                  between if and endif, if and  only  if  the  search
                  string   matches  (does  not  match)  pattern.  The
                  if..endif can nest.

                  Note: do not prepend whitespace to patterns  inside
                  if..endif.

           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 charac-
           ter, 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 follow-
           ing  the  second slash with an `i' flag will reverse this.
           Other flags are `x' (disable extended expression  syntax),
           and  `m'  (enable  multi-line mode, that is, treat newline
           characters as special).

           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
           if !/^owner-/
           /^(.*)-outgoing@(.*)$/   550 Use ${1}@${2} instead
           endif

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

    EXAMPLE BODY FILTER MAP
           # First skip over base 64 encoded text to save CPU cycles.
           ~^[[:alnum:]+/]{60,}$~          OK

           # Put your own body patterns here.

    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)