    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,
           mail routing, or access control. These tables are usually in dbm or  db
           format.

           Alternatively,  lookup tables can be specified in POSIX regular expres-
           sion form. In this case, each input is compared against a list of  pat-
           terns.  When a match is found, the corresponding result is returned and
           the search is terminated.

           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. Use "postmap -hmq - <file"  for  header_checks(5)  pat-
           terns,  and  "postmap -bmq - <file" for body_checks(5) (Postfix 2.6 and
           later).

    COMPATIBILITY
           With Postfix version 2.2 and earlier specify "postmap -fq" to  query  a
           table that contains case sensitive patterns. Patterns are case insensi-
           tive by default.

    TABLE FORMAT
           The general form of a Postfix regular expression table is:

           /pattern/flags result
                  When pattern matches the input  string,  use  the  corresponding
                  result value.

           !/pattern/flags result
                  When  pattern  does  not  match the input string, use the corre-
                  sponding result value.

           if /pattern/flags

           endif  If the input string matches /pattern/,  then  match  that  input
                  string against the patterns between if and endif.  The if..endif
                  can nest.

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

                  This feature is available in Postfix 2.1 and later.

           if !/pattern/flags

           endif  If the input string does not match /pattern/,  then  match  that
                  input  string  against  the  patterns  between if and endif. The
                  if..endif can nest.

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

                  This feature is available in Postfix 2.1 and later.

           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.

           Each pattern is a POSIX regular expression enclosed by a pair of delim-
           iters. The regular expression syntax is documented in re_format(7) with
           4.4BSD, in regex(5) with Solaris, and in  regex(7)  with  Linux.  Other
           systems may use other document names.

           The  expression  delimiter  can  be  any  non-alphanumerical character,
           except whitespace or characters that have special  meaning  (tradition-
           ally  the  forward  slash  is used). The regular expression can contain
           whitespace.

           By default, matching is case-insensitive, and newlines are not  treated
           as  special  characters. The behavior is controlled by flags, which are
           toggled by appending one or more of the following characters after  the
           pattern:

           i (default: on)
                  Toggles  the case sensitivity flag. By default, matching is case
                  insensitive.

           m (default: off)
                  Toggle the multi-line mode flag. When this flag is on, the ^ and
                  $  metacharacters match immediately after and immediately before
                  a newline character, respectively, in addition  to  matching  at
                  the start and end of the input string.

           x (default: on)
                  Toggles the extended expression syntax flag. By default, support
                  for extended expression syntax is enabled.

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

           Each  pattern  is applied to the entire input 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 par-
           ent network search is done, and user@domain mail addresses are not bro-
           ken  up  into  their user and domain constituent parts, nor is user+foo
           broken up into user and foo.

    TEXT SUBSTITUTION
           Substitution of substrings (text that  matches  patterns  inside  "()")
           from  the  matched  expression into the result string is requested with
           $1, $2, etc.; specify $$ to produce  a  $  character  as  output.   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
           postmap(1), Postfix lookup table manager
           pcre_table(5), format of PCRE tables
           cidr_table(5), format of CIDR tables

    README FILES
           DATABASE_README, Postfix lookup table overview

    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

           Wietse Venema
           Google, Inc.
           111 8th Avenue
           New York, NY 10011, USA

                                                                   REGEXP_TABLE(5)