    CANONICAL(5)                                                      CANONICAL(5)

    NAME
           canonical - Postfix canonical table format

    SYNOPSIS
           postmap /etc/postfix/canonical

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

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

    DESCRIPTION
           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-
           sive.

           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 a TCP-based server. In those cases, the lookups are done in
           a slightly different way as described below under  "REGULAR  EXPRESSION
           TABLES" or "TCP-BASED TABLES".

           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
           parameter.

           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   =
           static:all".

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

           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.

    CASE FOLDING
           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.

    TABLE FORMAT
           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.

    TABLE SEARCH ORDER
           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-
                  dence.

                  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-
                  name.

           @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.

                  To avoid backscatter with mail for a wild-card  domain,  replace
                  the  wild-card  mapping  with  explicit  1:1  mappings, or add a
                  reject_unverified_recipient restriction for that domain:

                      smtpd_recipient_restrictions =
                          ...
                          reject_unauth_destination
                          check_recipient_access
                              inline:{example.com=reject_unverified_recipient}
                      unverified_recipient_reject_code = 550

                  In the above example, Postfix may contact a remote server if the
                  recipient is rewritten to a remote address.

    RESULT ADDRESS REWRITING
           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".

    ADDRESS EXTENSION
           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
           lookup.

    REGULAR EXPRESSION TABLES
           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.

    TCP-BASED TABLES
           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.

    BUGS
           The table format does not understand quoting conventions.

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

           canonical_classes  (envelope_sender, envelope_recipient, header_sender,
           header_recipient)
                  What addresses are subject to canonical_maps address mapping.

           canonical_maps (empty)
                  Optional  address  mapping lookup tables for message headers and
                  envelopes.

           recipient_canonical_maps (empty)
                  Optional address mapping lookup tables for envelope  and  header
                  recipient addresses.

           sender_canonical_maps (empty)
                  Optional  address  mapping lookup tables for envelope and header
                  sender addresses.

           propagate_unmatched_extensions (canonical, virtual)
                  What address lookup tables copy an address  extension  from  the
                  lookup key to the lookup result.

           Other parameters of interest:

           inet_interfaces (all)
                  The  local  network  interface  addresses  that this mail system
                  receives mail on.

           local_header_rewrite_clients (permit_inet_interfaces)
                  Rewrite or add message  headers  in  mail  from  these  clients,
                  updating  incomplete addresses with the domain name in $myorigin
                  or $mydomain, and adding missing headers.

           proxy_interfaces (empty)
                  The remote network interface addresses  that  this  mail  system
                  receives  mail  on by way of a proxy or network address transla-
                  tion unit.

           masquerade_classes (envelope_sender, header_sender, header_recipient)
                  What addresses are subject to address masquerading.

           masquerade_domains (empty)
                  Optional list of  domains  whose  subdomain  structure  will  be
                  stripped off in email addresses.

           masquerade_exceptions (empty)
                  Optional  list  of  user names that are not subjected to address
                  masquerading,  even  when  their   addresses   match   $masquer-
                  ade_domains.

           mydestination ($myhostname, localhost.$mydomain, localhost)
                  The  list of domains that are delivered via the $local_transport
                  mail delivery transport.

           myorigin ($myhostname)
                  The domain name that locally-posted mail appears to  come  from,
                  and that locally posted mail is delivered to.

           owner_request_special (yes)
                  Enable  special  treatment  for  owner-listname  entries  in the
                  aliases(5)  file,  and  don't  split  owner-listname  and  list-
                  name-request  address localparts when the recipient_delimiter is
                  set to "-".

           remote_header_rewrite_domain (empty)
                  Rewrite or add message headers in mail from  remote  clients  if
                  the  remote_header_rewrite_domain  parameter value is non-empty,
                  updating incomplete addresses with the domain specified  in  the
                  remote_header_rewrite_domain parameter, and adding missing head-
                  ers.

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

    README FILES
           DATABASE_README, Postfix lookup table overview
           ADDRESS_REWRITING_README, address rewriting guide

    LICENSE
           The Secure Mailer license must be distributed with this software.

    AUTHOR(S)
           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

                                                                      CANONICAL(5)