<header>Allow untrusted routing</header>

<center><tt>allow_untrusted_routing</tt></center>
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This parameter controls if Postfix will forward mail with sender-specified
routing (user[@%!]remote[@%!]site) from untrusted clients to destinations that
are blessed by the <a href=opt_relay_domains><tt>relay_domains</tt></a>
parameter.

<p>

By default, untrusted clients are not allowed to specify routing.
This closes a nasty open relay loophole where a backup MX host can
be tricked into forwarding junk mail to a primary MX host which
then spams it out to the world.


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