<header>Virtual Domains</header>
The optional virtual table specifies redirections for local and non-local
recipients or domains. The redirections are used by the cleanup(8) daemon. The
redirections are recursive.
<p>
The virtual redirection is applied only to the recipient envelope address, and
does not affect message headers. Think Sendmail rule set <tt>S0</tt>, if you
like. Use <a href=canonical>canonical mapping</a> to rewrite header and
envelope addresses in general.
<p>
Typical support for a virtual domain looks like the following:
<ul>
<li> <b><tt>virtual.domain</tt></b> mapped to... <b><tt>anything</tt></b> (right-hand content does not matter)
<li> <b><tt>user1@virtual.domain</tt></b> mapped to... <b><tt>address1</tt></b>
<li> <b><tt>user2@virtual.domain</tt></b> mapped to... <b><tt>address2,
address3</tt></b>
</ul>
With this, the SMTP server accepts mail for <tt>virtual.domain</tt> and rejects mail for
<tt>unknown@virtual.domain</tt> as undeliverable.
<p>
The format of the virtual table is as follows, mappings being tried in the
order as listed here:
<ul>
<li> <b><tt>user@domain</tt></b> mapped to... <b><tt>address, address, ...</tt></b>: Mail for
<tt>user@domain</tt> is redirected to <tt>address</tt>. This form has the
highest precedence.
<li> <b><tt>user</tt></b> mapped to... <b><tt>address, address, ...</tt></b>: Mail for <tt>user@site</tt>
is redirected to <tt>address</tt> when site is equal to <tt>$myorigin</tt> when
site is listed in <tt>$mydestination</tt>, or when it is listed in
<tt>$inet_interfaces</tt>. This functionality overlaps with functionality of
the <a href=aliases>local alias</a> database. The difference is that virtual mapping can be
applied to non-local addresses.
<li> <b><tt>@domain</tt></b> mapped to... <b><tt>address, address, ...</tt></b>: Mail for any user in
<tt>domain</tt> is redirected to <tt>address</tt>. This form has the lowest
precedence.
</ul>
In all the above forms, when address has the form <tt>@otherdomain</tt>, the
result is the same user in otherdomain. This works for the first address in the
expansion only.
<p>
ADDRESS EXTENSION: When the search fails, and the address localpart contains
the optional recipient delimiter (e.g., <tt>user+foo@domain</tt>), the search
is repeated for the unextended address (e.g. <tt>user@domain</tt>), and the
unmatched address extension is propagated to the result of expansion. The
matching order is: <tt>user+foo@domain</tt>, <tt>user@domain</tt>,
<tt>user+foo</tt>, <tt>user</tt>, and <tt>@domain</tt>.
<hr>
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