CANONICAL
Section: File Formats (5)
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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, 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 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
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- CASE FOLDING
-
- TABLE FORMAT
-
- TABLE SEARCH ORDER
-
- RESULT ADDRESS REWRITING
-
- ADDRESS EXTENSION
-
- REGULAR EXPRESSION TABLES
-
- TCP-BASED TABLES
-
- BUGS
-
- CONFIGURATION PARAMETERS
-
- SEE ALSO
-
- README FILES
-
- LICENSE
-
- AUTHOR(S)
-
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