NAME
Forward Confirmed RDNS - http://en.wikipedia.org/wiki/FCrDNS
DESCRIPTION
Determine if the SMTP sender has matching forward and reverse DNS.
Sets the connection note fcrdns.
WHY IT WORKS
The reverse DNS of zombie PCs is out of the spam operators control.
Their only way to pass this test is to limit themselves to hosts with
matching forward and reverse DNS. At present, this presents a
significant hurdle.
There's more POD that explains the tests, config settings, and method.
Much like many other plugins, fcrdns is not reliable enough (only about 90%)
to use for message rejection. However, when combined with any sort of
heuristics system such as the karma plugin, the fcrdns plugin provides another
extremely reliable indication of spam likelihood.
Matt
