.\"	$NetBSD: aliases.5,v 1.4.2.1 2023/12/25 12:43:27 martin Exp $
.\"
.TH ALIASES 5 
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.SH NAME
aliases
\-
Postfix local alias database format
.SH "SYNOPSIS"
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.nf
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\fBnewaliases\fR
.SH DESCRIPTION
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The \fBaliases\fR(5) table provides a system\-wide mechanism to
redirect mail for local recipients. The redirections are
processed by the Postfix \fBlocal\fR(8) delivery agent.

Normally, the \fBaliases\fR(5) table is specified as a text file
that serves as input to the \fBpostalias\fR(1) command. The
result, an indexed file in \fBdbm\fR or \fBdb\fR format, is
used for fast lookup by the mail system. Execute the command
\fBnewaliases\fR 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 \fB.forward\fR files in their home directory.
Lines in per\-user \fB.forward\fR files have the same syntax
as the right\-hand side of \fBaliases\fR(5) entries.

The format of the alias database input file is as follows:
.IP \(bu
An alias definition has the form
.sp
.nf
     \fIname\fR: \fIvalue1\fR, \fIvalue2\fR, \fI...\fR
.fi
.IP \(bu
Empty lines and whitespace\-only lines are ignored, as
are lines whose first non\-whitespace character is a `#'.
.IP \(bu
A logical line starts with non\-whitespace text. A line that
starts with whitespace continues a logical line.
.PP
The \fIname\fR is a local address (no domain part).
Use double quotes when the name contains any special characters
such as whitespace, `#', `:', or `@'. The \fIname\fR is folded to
lowercase, in order to make database lookups case insensitive.
.PP
In addition, when an alias exists for \fBowner\-\fIname\fR,
this will override the envelope sender address, so that
delivery diagnostics are directed to \fBowner\-\fIname\fR,
instead of the originator of the message (for details, see
\fBowner_request_special\fR, \fBexpand_owner_alias\fR and
\fBreset_owner_alias\fR).
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.
.PP
The \fIvalue\fR contains one or more of the following:
.IP \fIaddress\fR
Mail is forwarded to \fIaddress\fR, which is compatible
with the RFC 822 standard.
.IP \fI/file/name\fR
Mail is appended to \fI/file/name\fR. For details on how a
file is written see the sections "EXTERNAL FILE DELIVERY"
and "DELIVERY RIGHTS" in the \fBlocal\fR(8) documentation.
Delivery is not limited to regular files.  For example, to dispose
of unwanted mail, deflect it to \fB/dev/null\fR.
.IP "|\fIcommand\fR"
Mail is piped into \fIcommand\fR. Commands that contain
special characters, such as whitespace, should be enclosed
between double quotes. For details on how a command is
executed see "EXTERNAL COMMAND DELIVERY" and "DELIVERY
RIGHTS" in the \fBlocal\fR(8) documentation.
.sp
When the command fails, a limited amount of command output is
mailed back to the sender.  The file \fB/usr/include/sysexits.h\fR
defines the expected exit status codes. For example, use
\fB"|exit 67"\fR to simulate a "user unknown" error, and
\fB"|exit 0"\fR to implement an expensive black hole.
.IP \fB:include:\fI/file/name\fR
Mail is sent to the destinations listed in the named file.
Lines in \fB:include:\fR files have the same syntax
as the right\-hand side of alias entries.
.sp
A destination can be any destination that is described in this
manual page. However, delivery to "|\fIcommand\fR" and
\fI/file/name\fR is disallowed by default. To enable, edit the
\fBallow_mail_to_commands\fR and \fBallow_mail_to_files\fR
configuration parameters.
.SH "ADDRESS EXTENSION"
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.nf
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When alias database search fails, and the recipient localpart
contains the optional recipient delimiter (e.g., \fIuser+foo\fR),
the search is repeated for the unextended address (e.g., \fIuser\fR).

The \fBpropagate_unmatched_extensions\fR parameter controls
whether an unmatched address extension (\fI+foo\fR) is
propagated to the result of table lookup.
.SH "CASE FOLDING"
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.nf
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The local(8) delivery agent always folds the search string
to lowercase before database lookup.
.SH "REGULAR EXPRESSION TABLES"
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.nf
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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 \fBregexp_table\fR(5)
or \fBpcre_table\fR(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 \fIuser+foo\fR is not broken
up into \fIuser\fR and \fIfoo\fR.

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 \fB$1\fR,
\fB$2\fR etc. substring interpolation.
.SH "SECURITY"
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The \fBlocal\fR(8) delivery agent disallows regular expression
substitution of $1 etc. in \fBalias_maps\fR, because that
would open a security hole.

The \fBlocal\fR(8) delivery agent will silently ignore
requests to use the \fBproxymap\fR(8) server within
\fBalias_maps\fR. Instead it will open the table directly.
Before Postfix version 2.2, the \fBlocal\fR(8) delivery
agent will terminate with a fatal error.
.SH "CONFIGURATION PARAMETERS"
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The following \fBmain.cf\fR parameters are especially relevant.
The text below provides only a parameter summary. See
\fBpostconf\fR(5) for more details including examples.
.IP "\fBalias_database (see 'postconf -d' output)\fR"
The alias databases for \fBlocal\fR(8) delivery that are updated with
"\fBnewaliases\fR" or with "\fBsendmail \-bi\fR".
.IP "\fBalias_maps (see 'postconf -d' output)\fR"
The alias databases that are used for \fBlocal\fR(8) delivery.
.IP "\fBallow_mail_to_commands (alias, forward)\fR"
Restrict \fBlocal\fR(8) mail delivery to external commands.
.IP "\fBallow_mail_to_files (alias, forward)\fR"
Restrict \fBlocal\fR(8) mail delivery to external files.
.IP "\fBexpand_owner_alias (no)\fR"
When delivering to an alias "\fIaliasname\fR" that has an
"owner\-\fIaliasname\fR" companion alias, set the envelope sender
address to the expansion of the "owner\-\fIaliasname\fR" alias.
.IP "\fBpropagate_unmatched_extensions (canonical, virtual)\fR"
What address lookup tables copy an address extension from the lookup
key to the lookup result.
.IP "\fBowner_request_special (yes)\fR"
Enable special treatment for owner\-\fIlistname\fR entries in the
\fBaliases\fR(5) file, and don't split owner\-\fIlistname\fR and
\fIlistname\fR\-request address localparts when the recipient_delimiter
is set to "\-".
.IP "\fBrecipient_delimiter (empty)\fR"
The set of characters that can separate an email address
localpart, user name, or a .forward file name from its extension.
.PP
Available in Postfix version 2.3 and later:
.IP "\fBfrozen_delivered_to (yes)\fR"
Update the \fBlocal\fR(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.
.SH "STANDARDS"
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RFC 822 (ARPA Internet Text Messages)
.SH "SEE ALSO"
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local(8), local delivery agent
newaliases(1), create/update alias database
postalias(1), create/update alias database
postconf(5), configuration parameters
.SH "README FILES"
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Use "\fBpostconf readme_directory\fR" or
"\fBpostconf html_directory\fR" to locate this information.
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DATABASE_README, Postfix lookup table overview
.SH "LICENSE"
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The Secure Mailer license must be distributed with this software.
.SH "AUTHOR(S)"
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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