You really do not need to do this in spamd. Do it in pf.
i.e:

table <nospamd> persist file "/etc/mail/nogreylist"
....
no rdr $ext_if proto tcp from <nospamd> to $mailserver port smtp


* Stuart Henderson <stu@spacehopper.org> [2005-07-26 04:23]:
> I seem to remember seeing a patch to spamd that makes greylisting only
> look at the first /24 of the address, but I can't find it after fairly
> extensive searching with google/marc. Does anyone have a copy they
> could point me at?
>
> The whitelists on puremagic.com (on which greylisting.org's lists are
> based) don't list networks with a common spool unless more than a /24
> is involved (there are some /24 listed with other factors requiring
> whitelisting, e.g. unique sender addresses per delivery attempt).
>

--
Bob Beck Computing and Network Services
beck@bofh.ucs.ualberta.ca University of Alberta
True Evil hides its real intentions in its street address.