# phpman > man > regexp_table(5) [REGEXP_TABLE(5)](https://www.chedong.com/phpMan.php/man/REGEXPTABLE/5/markdown) File Formats Manual [REGEXP_TABLE(5)](https://www.chedong.com/phpMan.php/man/REGEXPTABLE/5/markdown) ## 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 expression form. In this case, each input is compared against a list of patterns. 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)](https://www.chedong.com/phpMan.php/man/headerchecks/5/markdown) patterns, and "**postmap** **-bmq** **-** <_file_" for [body_checks(5)](https://www.chedong.com/phpMan.php/man/bodychecks/5/markdown) (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 insensitive 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 corresponding _result_ value. **if** **/**_pattern_**/**_flags_ **endif** If the input string matches /_pattern_/, then match that input string against the pat‐ terns 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-white‐ space 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 delimiters. The regular ex‐ pression syntax is documented in **re**___**[format**(7)](https://www.chedong.com/phpMan.php/man/format/7/markdown) with 4.4BSD, in [**regex**(5)](https://www.chedong.com/phpMan.php/man/regex/5/markdown) with Solaris, and in [**regex**(7)](https://www.chedong.com/phpMan.php/man/regex/7/markdown) with Linux. Other systems may use other document names. The expression delimiter can be any non-alphanumerical character, except whitespace or char‐ acters that have special meaning (traditionally the forward slash is used). The regular ex‐ pression 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 fol‐ lowing 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 expres‐ sion 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 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 (text that matches patterns inside "()") from the matched expres‐ sion into the result string is requested with $1, $2, etc.; specify $$ to produce a $ charac‐ ter 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)](https://www.chedong.com/phpMan.php/man/postmap/1/markdown), Postfix lookup table manager [pcre_table(5)](https://www.chedong.com/phpMan.php/man/pcretable/5/markdown), format of PCRE tables [cidr_table(5)](https://www.chedong.com/phpMan.php/man/cidrtable/5/markdown), format of CIDR tables ## README FILES Use "**postconf** **readme**___**directory**" or "**postconf** **html**___**directory**" to locate this information. DATABASE_README, Postfix lookup table overview **AUTHOR(S)** The regexp table lookup code was originally written by: LaMont Jones That code was based on the PCRE dictionary contributed by: Andrew McNamara 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)](https://www.chedong.com/phpMan.php/man/REGEXPTABLE/5/markdown)