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VIRTUAL(5) VIRTUAL(5)
<b>NAME</b>
virtual - Postfix virtual alias table format
<b>SYNOPSIS</b>
<b>postmap /etc/postfix/virtual</b>
<b>postmap -q "</b><i>string</i><b>" /etc/postfix/virtual</b>
<b>postmap -q - /etc/postfix/virtual</b> <<i>inputfile</i>
<b>DESCRIPTION</b>
The optional <a href="virtual.5.html"><b>virtual</b>(5)</a> alias table rewrites recipient addresses for
all local, all virtual, and all remote mail destinations. This is
unlike the <a href="aliases.5.html"><b>aliases</b>(5)</a> table which is used only for <a href="local.8.html"><b>local</b>(8)</a> delivery.
Virtual aliasing is recursive, and is implemented by the Postfix
<a href="cleanup.8.html"><b>cleanup</b>(8)</a> daemon before mail is queued.
The main applications of virtual aliasing are:
<b>o</b> To redirect mail for one address to one or more addresses.
<b>o</b> To implement virtual alias domains where all addresses are
aliased to addresses in other domains.
Virtual alias domains are not to be confused with the virtual
mailbox domains that are implemented with the Postfix <a href="virtual.8.html"><b>virtual</b>(8)</a>
mail delivery agent. With <a href="ADDRESS_CLASS_README.html#virtual_mailbox_class">virtual mailbox domains</a>, each recipi-
ent address can have its own mailbox.
Virtual aliasing is applied only to recipient envelope addresses, and
does not affect message headers. Use <a href="canonical.5.html"><b>canonical</b>(5)</a> mapping to rewrite
header and envelope addresses in general.
Normally, the <a href="virtual.5.html"><b>virtual</b>(5)</a> alias table is specified as a text file that
serves as input to the <a href="postmap.1.html"><b>postmap</b>(1)</a> command. The result, an indexed file
in <b>dbm</b> or <b>db</b> format, is used for fast searching by the mail system.
Execute the command "<b>postmap /etc/postfix/virtual</b>" 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 case, the lookups are done in a
slightly different way as described below under "REGULAR EXPRESSION
TABLES" or "TCP-BASED TABLES".
<b>CASE FOLDING</b>
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 <a href="regexp_table.5.html">regexp</a>: or <a href="pcre_table.5.html">pcre</a>: whose lookup fields can match both upper and
lower case.
<b>TABLE FORMAT</b>
The input format for the <a href="postmap.1.html"><b>postmap</b>(1)</a> command is as follows:
<i>pattern address, address, ...</i>
When <i>pattern</i> matches a mail address, replace it by the corre-
sponding <i>address</i>.
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.
<b>TABLE SEARCH ORDER</b>
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:
<i>user</i>@<i>domain address, address, ...</i>
Redirect mail for <i>user</i>@<i>domain</i> to <i>address</i>. This form has the
highest precedence.
<i>user address, address, ...</i>
Redirect mail for <i>user</i>@<i>site</i> to <i>address</i> when <i>site</i> is equal to
$<b><a href="postconf.5.html#myorigin">myorigin</a></b>, when <i>site</i> is listed in $<b><a href="postconf.5.html#mydestination">mydestination</a></b>, or when it is
listed in $<b><a href="postconf.5.html#inet_interfaces">inet_interfaces</a></b> or $<b><a href="postconf.5.html#proxy_interfaces">proxy_interfaces</a></b>.
This functionality overlaps with functionality of the local
<i>aliases</i>(5) database. The difference is that <a href="virtual.5.html"><b>virtual</b>(5)</a> mapping
can be applied to non-local addresses.
@<i>domain address, address, ...</i>
Redirect mail for other users in <i>domain</i> to <i>address</i>. This form
has the lowest precedence.
Note: @<i>domain</i> is a wild-card. With this form, the Postfix SMTP
server accepts mail for any recipient in <i>domain</i>, regardless of
whether that recipient exists. This may turn your mail system
into a backscatter source: Postfix first accepts mail for non-
existent recipients and then tries to return that mail as "unde-
liverable" to the often forged sender address.
<b>RESULT ADDRESS REWRITING</b>
The lookup result is subject to address rewriting:
<b>o</b> When the result has the form @<i>otherdomain</i>, the result becomes
the same <i>user</i> in <i>otherdomain</i>. This works only for the first
address in a multi-address lookup result.
<b>o</b> When "<b><a href="postconf.5.html#append_at_myorigin">append_at_myorigin</a>=yes</b>", append "<b>@$<a href="postconf.5.html#myorigin">myorigin</a></b>" to addresses
without "@domain".
<b>o</b> When "<b><a href="postconf.5.html#append_dot_mydomain">append_dot_mydomain</a>=yes</b>", append "<b>.$<a href="postconf.5.html#mydomain">mydomain</a></b>" to addresses
without ".domain".
<b>ADDRESS EXTENSION</b>
When a mail address localpart contains the optional recipient delimiter
(e.g., <i>user+foo</i>@<i>domain</i>), the lookup order becomes: <i>user+foo</i>@<i>domain</i>,
<i>user</i>@<i>domain</i>, <i>user+foo</i>, <i>user</i>, and @<i>domain</i>.
The <b><a href="postconf.5.html#propagate_unmatched_extensions">propagate_unmatched_extensions</a></b> parameter controls whether an
unmatched address extension (<i>+foo</i>) is propagated to the result of table
lookup.
<b>VIRTUAL ALIAS DOMAINS</b>
Besides virtual aliases, the virtual alias table can also be used to
implement <a href="ADDRESS_CLASS_README.html#virtual_alias_class">virtual alias domains</a>. With a virtual alias domain, all
recipient addresses are aliased to addresses in other domains.
Virtual alias domains are not to be confused with the virtual mailbox
domains that are implemented with the Postfix <a href="virtual.8.html"><b>virtual</b>(8)</a> mail delivery
agent. With virtual mailbox domains, each recipient address can have
its own mailbox.
With a <a href="ADDRESS_CLASS_README.html#virtual_alias_class">virtual alias domain</a>, the virtual domain has its own user name
space. Local (i.e. non-virtual) usernames are not visible in a virtual
alias domain. In particular, local <a href="aliases.5.html"><b>aliases</b>(5)</a> and local mailing lists
are not visible as <i>localname@virtual-alias.domain</i>.
Support for a <a href="ADDRESS_CLASS_README.html#virtual_alias_class">virtual alias domain</a> looks like:
/etc/postfix/<a href="postconf.5.html">main.cf</a>:
<a href="postconf.5.html#virtual_alias_maps">virtual_alias_maps</a> = <a href="DATABASE_README.html#types">hash</a>:/etc/postfix/virtual
Note: some systems use <b>dbm</b> databases instead of <b>hash</b>. See the output
from "<b>postconf -m</b>" for available database types.
/etc/postfix/virtual:
<i>virtual-alias.domain anything</i> (right-hand content does not matter)
<i>postmaster@virtual-alias.domain postmaster</i>
<i>user1@virtual-alias.domain address1</i>
<i>user2@virtual-alias.domain address2, address3</i>
The <i>virtual-alias.domain anything</i> entry is required for a virtual alias
domain. <b>Without this entry, mail is rejected with "relay access</b>
<b>denied", or bounces with "mail loops back to myself".</b>
Do not specify <a href="ADDRESS_CLASS_README.html#virtual_alias_class">virtual alias domain</a> names in the <a href="postconf.5.html"><b>main.cf</a> <a href="postconf.5.html#mydestination">mydestination</a></b>
or <b><a href="postconf.5.html#relay_domains">relay_domains</a></b> configuration parameters.
With a <a href="ADDRESS_CLASS_README.html#virtual_alias_class">virtual alias domain</a>, the Postfix SMTP server accepts mail for
<i>known-user@virtual-alias.domain</i>, and rejects mail for <i>unknown-user</i>@<i>vir-</i>
<i>tual-alias.domain</i> as undeliverable.
Instead of specifying the virtual alias domain name via the <b><a href="postconf.5.html#virtual_alias_maps">vir</a>-</b>
<b><a href="postconf.5.html#virtual_alias_maps">tual_alias_maps</a></b> table, you may also specify it via the <a href="postconf.5.html"><b>main.cf</a> <a href="postconf.5.html#virtual_alias_domains">vir-</b>
<b>tual_alias_domains</a></b> configuration parameter. This latter parameter uses
the same syntax as the <a href="postconf.5.html"><b>main.cf</a> <a href="postconf.5.html#mydestination">mydestination</a></b> configuration parameter.
<b>REGULAR EXPRESSION TABLES</b>
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 <a href="regexp_table.5.html"><b>regexp_table</b>(5)</a> or <a href="pcre_table.5.html"><b>pcre_table</b>(5)</a>.
Each pattern is a regular expression that is applied to the entire
address being looked up. Thus, <i>user@domain</i> mail addresses are not bro-
ken up into their <i>user</i> and <i>@domain</i> constituent parts, nor is <i>user+foo</i>
broken up into <i>user</i> and <i>foo</i>.
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 interpo-
lated as <b>$1</b>, <b>$2</b> and so on.
<b>TCP-BASED TABLES</b>
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 <a href="tcp_table.5.html"><b>tcp_table</b>(5)</a>. This feature is not
available up to and including Postfix version 2.4.
Each lookup operation uses the entire address once. Thus, <i>user@domain</i>
mail addresses are not broken up into their <i>user</i> and <i>@domain</i> con-
stituent parts, nor is <i>user+foo</i> broken up into <i>user</i> and <i>foo</i>.
Results are the same as with indexed file lookups.
<b>BUGS</b>
The table format does not understand quoting conventions.
<b>CONFIGURATION PARAMETERS</b>
The following <a href="postconf.5.html"><b>main.cf</b></a> parameters are especially relevant to this topic.
See the Postfix <a href="postconf.5.html"><b>main.cf</b></a> file for syntax details and for default values.
Use the "<b>postfix reload</b>" command after a configuration change.
<b><a href="postconf.5.html#virtual_alias_maps">virtual_alias_maps</a></b>
List of virtual aliasing tables.
<b><a href="postconf.5.html#virtual_alias_domains">virtual_alias_domains</a></b>
List of <a href="ADDRESS_CLASS_README.html#virtual_alias_class">virtual alias domains</a>. This uses the same syntax as the
<b><a href="postconf.5.html#mydestination">mydestination</a></b> parameter.
<b><a href="postconf.5.html#propagate_unmatched_extensions">propagate_unmatched_extensions</a></b>
A list of address rewriting or forwarding mechanisms that propa-
gate an address extension from the original address to the
result. Specify zero or more of <b>canonical</b>, <b>virtual</b>, <b>alias</b>, <b>for-</b>
<b>ward</b>, <b>include</b>, or <b>generic</b>.
Other parameters of interest:
<b><a href="postconf.5.html#inet_interfaces">inet_interfaces</a></b>
The network interface addresses that this system receives mail
on. You need to stop and start Postfix when this parameter
changes.
<b><a href="postconf.5.html#mydestination">mydestination</a></b>
List of domains that this mail system considers local.
<b><a href="postconf.5.html#myorigin">myorigin</a></b>
The domain that is appended to any address that does not have a
domain.
<b><a href="postconf.5.html#owner_request_special">owner_request_special</a></b>
Give special treatment to <b>owner-</b><i>xxx</i> and <i>xxx</i><b>-request</b> addresses.
<b><a href="postconf.5.html#proxy_interfaces">proxy_interfaces</a></b>
Other interfaces that this machine receives mail on by way of a
proxy agent or network address translator.
<b>SEE ALSO</b>
<a href="cleanup.8.html">cleanup(8)</a>, canonicalize and enqueue mail
<a href="postmap.1.html">postmap(1)</a>, Postfix lookup table manager
<a href="postconf.5.html">postconf(5)</a>, configuration parameters
<a href="canonical.5.html">canonical(5)</a>, canonical address mapping
<b>README FILES</b>
<a href="ADDRESS_REWRITING_README.html">ADDRESS_REWRITING_README</a>, address rewriting guide
<a href="DATABASE_README.html">DATABASE_README</a>, Postfix lookup table overview
<a href="VIRTUAL_README.html">VIRTUAL_README</a>, domain hosting guide
<b>LICENSE</b>
The Secure Mailer license must be distributed with this software.
<b>AUTHOR(S)</b>
Wietse Venema
IBM T.J. Watson Research
P.O. Box 704
Yorktown Heights, NY 10598, USA
VIRTUAL(5)
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