The following received header gets RDNS_NONE:

Received: from [] (HELO
by (CommuniGate Pro SMTP 5.1.11)
with ESMTP id 60056 for jrudd@some.internal.test.domain; Tue, 31 Jul
2007 14:05:04 -0700

This is an error in the RDNS_NONE logic. The host in question DOES have
RDNS. The issue is that CommuniGate Pro doesn't put the RDNS
information into the Received header (and the place where it puts the
HELO information might instead have the authenticated user, if SMTP-AUTH
was used).

My recommendation is that the logic for RDNS_NONE should be:

if (Received =~ /\(CommuniGate Pro SMTP /) {
if (DNS checks are enabled) {
do the DNS check on the IP address, and then decide if it has RDNS
else {
don't trigger RDNS_NONE (because you can't know without the DNS
else { # not a CommuniGate Pro MTA
do existing RDNS_NONE logic