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man pages section 5: File Formats

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Updated: Wednesday, February 9, 2022

canonical (5)


canonical - Postfix canonical table format


postmap /etc/postfix/canonical

postmap -q "string" /etc/postfix/canonical

postmap -q - /etc/postfix/canonical <inputfile


CANONICAL(5)                  File Formats Manual                 CANONICAL(5)

       canonical - Postfix canonical table format

       postmap /etc/postfix/canonical

       postmap -q "string" /etc/postfix/canonical

       postmap -q - /etc/postfix/canonical <inputfile

       The  optional canonical(5) table specifies an address mapping for local
       and non-local addresses. The mapping is used by the cleanup(8)  daemon,
       before  mail  is  stored into the queue.  The address mapping is recur-

       Normally, the canonical(5) table is  specified  as  a  text  file  that
       serves as input to the postmap(1) command.  The result, an indexed file
       in dbm or db format, is used for fast searching  by  the  mail  system.
       Execute  the  command  "postmap  /etc/postfix/canonical"  to rebuild an
       indexed file after changing the corresponding text file.

       When the table is provided via other means such as NIS,  LDAP  or  SQL,
       the same lookups are done as for ordinary indexed files.

       Alternatively,  the  table  can be provided as a regular-expression map
       where patterns are given as regular  expressions,  or  lookups  can  be
       directed to TCP-based server. In those cases, the lookups are done in a
       slightly different way as described  below  under  "REGULAR  EXPRESSION

       By  default  the  canonical(5)  mapping  affects  both  message  header
       addresses (i.e. addresses that  appear  inside  messages)  and  message
       envelope  addresses  (for  example, the addresses that are used in SMTP
       protocol commands).  This  is  controlled  with  the  canonical_classes

       NOTE:  Postfix  versions  2.2  and  later  rewrite message headers from
       remote SMTP clients only if the  client  matches  the  local_header_re-
       write_clients parameter, or if the remote_header_rewrite_domain config-
       uration parameter specifies a non-empty  value.  To  get  the  behavior
       before    Postfix    2.2,   specify   "local_header_rewrite_clients   =

       Typically, one would use the canonical(5) table to replace login  names
       by Firstname.Lastname, or to clean up addresses produced by legacy mail

       The canonical(5) mapping is not to be confused with virtual alias  sup-
       port  or  with  local  aliasing.  To change the destination but not the
       headers, use the virtual(5) or aliases(5) map instead.

       The search string is folded to lowercase before database lookup. As  of
       Postfix  2.3,  the search string is not case folded with database types
       such as regexp: or pcre: whose lookup fields can match both  upper  and
       lower case.

       The input format for the postmap(1) command is as follows:

       pattern address
              When  pattern  matches  a mail address, replace it by the corre-
              sponding address.

       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.

       With lookups from indexed files such as DB or DBM,  or  from  networked
       tables  such  as  NIS,  LDAP  or SQL, each user@domain query produces a
       sequence of query patterns as described below.

       Each query pattern is sent to each specified lookup table before trying
       the next query pattern, until a match is found.

       user@domain address
              Replace user@domain by address. This form has the highest prece-

              This is useful to clean up addresses  produced  by  legacy  mail
              systems.   It  can  also  be  used to produce Firstname.Lastname
              style addresses, but see below for a simpler solution.

       user address
              Replace user@site by address when site is  equal  to  $myorigin,
              when  site  is listed in $mydestination, or when it is listed in
              $inet_interfaces or $proxy_interfaces.

              This form is useful for replacing login names by Firstname.Last-

       @domain address
              Replace other addresses in domain by address.  This form has the
              lowest precedence.

              Note: @domain is a wild-card.  When  this  form  is  applied  to
              recipient  addresses,  the  Postfix SMTP server accepts mail for
              any recipient in domain, regardless of  whether  that  recipient
              exists.   This  may  turn  your  mail  system into a backscatter
              source: Postfix first accepts mail for  non-existent  recipients
              and  then  tries  to  return that mail as "undeliverable" to the
              often forged sender address.

       The lookup result is subject to address rewriting:

       o      When the result has the form @otherdomain,  the  result  becomes
              the same user in otherdomain.

       o      When  "append_at_myorigin=yes", append "@$myorigin" to addresses
              without "@domain".

       o      When "append_dot_mydomain=yes", append ".$mydomain" to addresses
              without ".domain".

       When a mail address localpart contains the optional recipient delimiter
       (e.g., user+foo@domain), the  lookup  order  becomes:  user+foo@domain,
       user@domain, user+foo, user, and @domain.

       The   propagate_unmatched_extensions   parameter  controls  whether  an
       unmatched address extension (+foo) is propagated to the result of table

       This  section  describes how the table lookups change when the table is
       given in the form of regular expressions. For a description of  regular
       expression lookup table syntax, see regexp_table(5) or pcre_table(5).

       Each  pattern  is  a  regular  expression that is applied to the entire
       address being looked up. Thus, 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.

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

       Results  are the same as with indexed file lookups, with the additional
       feature that parenthesized substrings from the pattern can be  interpo-
       lated as $1, $2 and so on.

       This  section  describes  how the table lookups change when lookups are
       directed  to  a  TCP-based  server.  For  a  description  of  the   TCP
       client/server  lookup  protocol, see tcp_table(5).  This feature is not
       available up to and including Postfix version 2.4.

       Each lookup operation uses the entire address once.  Thus,  user@domain
       mail  addresses  are  not  broken  up  into their user and @domain con-
       stituent parts, nor is user+foo broken up into user and foo.

       Results are the same as with indexed file lookups.

       The table format does not understand quoting conventions.

       The following main.cf parameters are  especially  relevant.   The  text
       below  provides  only  a  parameter  summary.  See postconf(5) for more
       details including examples.

              What addresses are subject to canonical address mapping.

              List of canonical mapping tables.

              Address mapping lookup table for envelope and  header  recipient

              Address  mapping  lookup  table  for  envelope and header sender

              A list of address rewriting or forwarding mechanisms that propa-
              gate  an  address  extension  from  the  original address to the
              result.  Specify zero or more of canonical, virtual, alias, for-
              ward, include, or generic.

       Other parameters of interest:

              The  network  interface addresses that this system receives mail
              on.  You need to stop and  start  Postfix  when  this  parameter

              Rewrite  message header addresses in mail from these clients and
              update incomplete addresses with the domain name in $myorigin or
              $mydomain;  either  don't  rewrite  message  headers  from other
              clients at all, or rewrite message headers and update incomplete
              addresses  with  the  domain  specified in the remote_header_re-
              write_domain parameter.

              Other interfaces that this machine receives mail on by way of  a
              proxy agent or network address translator.

              List of address classes subject to masquerading: zero or more of
              envelope_sender,       envelope_recipient,        header_sender,

              List of domains that hide their subdomain structure.

              List of user names that are not subject to address masquerading.

              List of domains that this mail system considers local.

              The domain that is appended to locally-posted mail.

              Give special treatment to owner-xxx and xxx-request addresses.

              Don't  rewrite  message  headers from remote clients at all when
              this parameter is empty; otherwise, rewrite message headers  and
              append the specified domain name to incomplete addresses.

       See attributes(7) for descriptions of the following attributes:

       |ATTRIBUTE TYPE |       ATTRIBUTE VALUE        |
       |Availability   | service/network/smtp/postfix |
       |Stability      | Volatile                     |

       cleanup(8), canonicalize and enqueue mail
       postmap(1), Postfix lookup table manager
       postconf(5), configuration parameters
       virtual(5), virtual aliasing

       Use  "postconf readme_directory" or "postconf html_directory" to locate
       this information.
       DATABASE_README, Postfix lookup table overview
       ADDRESS_REWRITING_README, address rewriting guide

       The Secure Mailer license must be distributed with this software.

       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

       Source code for open source software components in Oracle Solaris can
       be found at https://www.oracle.com/downloads/opensource/solaris-source-

       This software was built from source available at
       https://github.com/oracle/solaris-userland.  The original community
       source was downloaded from  https://archive.mgm51.com/mirrors/postfix-

       Further information about this software can be found on the open source
       community website at http://www.postfix.org.