    REGEXP_TABLE(5)                                   REGEXP_TABLE(5)

    NAME
           regexp_table - format of Postfix regular expression tables

    SYNOPSIS
           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.

    TABLE FORMAT
           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  Examine the lines between if..endif only if pattern
                  matches (does not match). The if..endif  can  nest.
                  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).

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

           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.

    TEXT SUBSTITUTION
           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.

           Note: since negated patterns (those preceded by !)  return
           a result when the expression does not match, substitutions
           are not available for negated patterns.

    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
           cidr_table(5) format of CIDR tables
           tcp_table(5) TCP client/server table lookup protocol

    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)