Now, from your logs, just how much legitimate mail do you get that comes from an IP without PTR RR, and how much is that expressed as a percentage of legitimate incoming mail to your lists? How much is that as a percentage of spam inbound to your list [to be fair, let's make it "spam that would not have been stopped by your other filters]?
well, it's gonna be hard to quantify what spam filters, bounces, ... rejected, and especially to associate them with smtp connections. but here are some simple data. yesterday, a saturday (gmt clock) 48293 total incoming smtp connections 6226 from ip addresses for which no ptr exists (12.89%) 12416 unique ip addresses which connected to server 3112 unique ip addresses for which no ptr exists (25.06%) some inferences might be drawn, but i am hesitant to do so. what numbers do YOU have for your server(s)? randy