Provided by: postfix_3.1.0-3ubuntu0.4_amd64 bug

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
       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 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_rewrite_clients parameter, or if the remote_header_rewrite_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-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,
       patterns are tried in the order as listed below:

       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 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.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.

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 otherdomain.

       •      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@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 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  parenthesized
       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  parameter
       summary. See postconf(5) for more details including examples.

       canonical_classes
              What addresses are subject to canonical address mapping.

       canonical_maps
              List of canonical mapping tables.

       recipient_canonical_maps
              Address mapping lookup table for envelope and header recipient addresses.

       sender_canonical_maps
              Address mapping lookup table for envelope and header sender addresses.

       propagate_unmatched_extensions
              A  list of address rewriting or forwarding mechanisms that propagate an address extension from the
              original address to the result.  Specify zero or  more  of  canonical,  virtual,  alias,  forward,
              include, or generic.

       Other parameters of interest:

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

       local_header_rewrite_clients
              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_rewrite_domain parameter.

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

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

       masquerade_domains
              List of domains that hide their subdomain structure.

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

       mydestination
              List of domains that this mail system considers local.

       myorigin
              The domain that is appended to locally-posted mail.

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

       remote_header_rewrite_domain
              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)