You'd better read:

http://freshmeat.net/articles/view/964/

or some pages listing many spam filters.

From: Jose Maria Sarachaga <sarachaga@...>
Subject: [jf] Reverse DNS lookup help
Date: Tue, 29 Jun 2004 19:38:24 -0700 (PDT)

> Hi list!
>
> I'm a Junkfilter newbie and i would like to know how
> to make reverse DNS lookups to reduce the crap, what
> code lines to add to my junkfilterrc file, or if there
> is any better solution, for example, spamcop.net, but
> don't know how to use it, in fact no idea :(
>
> Any help? resources?
> Thanks to you all
> Chema

--
Nothing but a peace sign.
MATSUDA Yoh-ichi(yoh)
mailto:yoh@...
http://www.flcl.org/~yoh/index.htm