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CANONICAL(5)                             File Formats Manual                            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 ad‐
       dresses. The mapping is used by the cleanup(8) daemon, before mail is stored into the  queue.
       The address mapping is recursive.

       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 TA‐
       BLES" 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_rewrite_clients parameter, or if the remote_header_re‐
       write_domain configuration 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  support  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 corresponding address.

       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.

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 pat‐
       tern, until a match is found.

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

              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 solu‐
              tion.

       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.Lastname.

       @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 rewrit‐
              ten to a remote address.

RESULT ADDRESS REWRITING
       The lookup result is subject to address rewriting:

       •      When the result has the form @otherdomain, the result becomes the same user in  other‐
              domain.

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

       •      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@do‐
       main), 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  reg‐‐
       exp_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 broken 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 parenthe‐
       sized substrings from the pattern can be interpolated 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 constituent 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 pa‐
       rameter 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 network interface addresses that this mail system receives mail on.

       local_header_rewrite_clients (permit_inet_interfaces)
              Rewrite  message header addresses in mail from these clients and update incomplete ad‐
              dresses 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_rewrite_domain parameter.

       proxy_interfaces (empty)
              The network interface addresses that this mail system receives mail on  by  way  of  a
              proxy or network address translation 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 ad‐
              dresses.

       masquerade_exceptions (empty)
              Optional list of user names that are not subjected to address masquerading, even  when
              their address matches $masquerade_domains.

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

       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 listname-request address localparts when the recipient_delim‐
              iter is set to "-".

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

README FILES
       Use "postconf readme_directory" or "postconf html_directory" to locate this information.
       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)