Updated: 2022/Sep/29
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ALIASES(5) File Formats Manual ALIASES(5)
NAME
aliases - Postfix local alias database format
SYNOPSIS
newaliases
DESCRIPTION
The aliases(5) table provides a system-wide mechanism to redirect mail
for local recipients. The redirections are processed by the Postfix
local(8) delivery agent.
Normally, the aliases(5) table is specified as a text file that serves
as input to the postalias(1) command. The result, an indexed file in
dbm or db format, is used for fast lookup by the mail system. Execute
the command newaliases in order to rebuild the indexed file after
changing the Postfix alias database.
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. In this case, the
lookups are done in a slightly different way as described below under
"REGULAR EXPRESSION TABLES".
Users can control delivery of their own mail by setting up .forward
files in their home directory. Lines in per-user .forward files have
the same syntax as the right-hand side of aliases(5) entries.
The format of the alias database input file is as follows:
⊕ An alias definition has the form
name: value1, value2, ...
⊕ Empty lines and whitespace-only lines are ignored, as are lines
whose first non-whitespace character is a `#'.
⊕ A logical line starts with non-whitespace text. A line that
starts with whitespace continues a logical line.
The name is a local address (no domain part). Use double quotes when
the name contains any special characters such as whitespace, `#', `:',
or `@'. The name is folded to lowercase, in order to make database
lookups case insensitive.
In addition, when an alias exists for owner-name, this will override
the envelope sender address, so that delivery diagnostics are directed
to owner-name, instead of the originator of the message (for details,
see owner_request_special, expand_owner_alias and reset_owner_alias).
This is typically used to direct delivery errors to the maintainer of a
mailing list, who is in a better position to deal with mailing list
delivery problems than the originator of the undelivered mail.
The value contains one or more of the following:
address
Mail is forwarded to address, which is compatible with the RFC
822 standard.
/file/name
Mail is appended to /file/name. See local(8) for details of
delivery to file. Delivery is not limited to regular files.
For example, to dispose of unwanted mail, deflect it to
/dev/null.
|command
Mail is piped into command. Commands that contain special
characters, such as whitespace, should be enclosed between
double quotes. See local(8) for details of delivery to command.
When the command fails, a limited amount of command output is
mailed back to the sender. The file /usr/include/sysexits.h
defines the expected exit status codes. For example, use "|exit
67" to simulate a "user unknown" error, and "|exit 0" to
implement an expensive black hole.
:include:/file/name
Mail is sent to the destinations listed in the named file.
Lines in :include: files have the same syntax as the right-hand
side of alias entries.
A destination can be any destination that is described in this
manual page. However, delivery to "|command" and /file/name is
disallowed by default. To enable, edit the
allow_mail_to_commands and allow_mail_to_files configuration
parameters.
ADDRESS EXTENSION
When alias database search fails, and the recipient localpart contains
the optional recipient delimiter (e.g., user+foo), the search is
repeated for the unextended address (e.g., user).
The propagate_unmatched_extensions parameter controls whether an
unmatched address extension (+foo) is propagated to the result of table
lookup.
CASE FOLDING
The local(8) delivery agent always folds the search string to lowercase
before database 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).
NOTE: these formats do not use ":" at the end of a pattern.
Each regular expression is applied to the entire search string. Thus, a
search string user+foo is not broken up into user and foo.
Regular expressions are applied in the order as specified in the table,
until a regular expression is found that matches the search string.
Lookup results are the same as with indexed file lookups. For security
reasons there is no support for $1, $2 etc. substring interpolation.
SECURITY
The local(8) delivery agent disallows regular expression substitution
of $1 etc. in alias_maps, because that would open a security hole.
The local(8) delivery agent will silently ignore requests to use the
proxymap(8) server within alias_maps. Instead it will open the table
directly. Before Postfix version 2.2, the local(8) delivery agent will
terminate with a fatal error.
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.
alias_database (see 'postconf -d' output)
The alias databases for local(8) delivery that are updated with
"newaliases" or with "sendmail -bi".
alias_maps (see 'postconf -d' output)
The alias databases that are used for local(8) delivery.
allow_mail_to_commands (alias, forward)
Restrict local(8) mail delivery to external commands.
allow_mail_to_files (alias, forward)
Restrict local(8) mail delivery to external files.
expand_owner_alias (no)
When delivering to an alias "aliasname" that has an
"owner-aliasname" companion alias, set the envelope sender
address to the expansion of the "owner-aliasname" alias.
propagate_unmatched_extensions (canonical, virtual)
What address lookup tables copy an address extension from the
lookup key to the lookup result.
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_delimiter
is set to "-".
recipient_delimiter (empty)
The set of characters that can separate an email address
localpart, user name, or a .forward file name from its
extension.
Available in Postfix version 2.3 and later:
frozen_delivered_to (yes)
Update the local(8) delivery agent's idea of the Delivered-To:
address (see prepend_delivered_header) only once, at the start
of a delivery attempt; do not update the Delivered-To: address
while expanding aliases or .forward files.
STANDARDS
RFC 822 (ARPA Internet Text Messages)
SEE ALSO
local(8), local delivery agent
newaliases(1), create/update alias database
postalias(1), create/update alias database
postconf(5), configuration parameters
README FILES
Use "postconf readme_directory" or "postconf html_directory" to locate
this information.
DATABASE_README, Postfix lookup table overview
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
ALIASES(5)