>What do you think of the list? The one that stood out was dul.dnsbl.sorbs.net as one I hadn't seen mentioned recently. I tried it on one high-volume site in WARN mode and got tons of hits in one hour.
Put it in WARN mode for a few days at the end of your restriction list and then see catches any legit. You could whitelist them and then switch to reject mode for the rest. You may not see much help from dul RBL if you're running greylist before the dul. Len
