ALIASES(5)

NAME
aliases - format of the Postfix alias database

SYNOPSIS
newaliases

DESCRIPTION
The aliases 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 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. The input and output file formats are expected to be compatible with Sendmail version 8, and are expected to be suitable for the use as NIS maps. 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 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, delivery diagnostics are directed to that address, instead of to the originator. This is typically used to direct delivery errors to the owner 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).

CONFIGURATION PARAMETERS
The following main.cf parameters are especially relevant to this topic. See the Postfix main.cf file for syntax details and for default values. Use the postfix reload command after a configuration change.

alias_maps
    List of alias databases.

allow_mail_to_commands
    Restrict the usage of mail delivery to external command.

allow_mail_to_files
    Restrict the usage of mail delivery to external file.

expand_owner_alias
    When delivering to an alias that has an owner- companion alias, set the envelope sender address to the right-hand side of the owner alias, instead using of the left-hand side address.

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

recipient_delimiter
    Delimiter that separates recipients from address extensions.

BUGS
Regular expression alias lookup tables are allowed, but substitution of $1 etc. is forbidden because that would open a security loophole.

STANDARDS
RFC 822 (ARPA Internet Text Messages)

SEE ALSO
local(8) local delivery agent
newaliases(1) alias database management
regexp_table(5) POSIX regular expression table format
pcre_table(5) Perl Compatible Regular Expression table format

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