> I don't see that sort of probing on our MXs, except on rare occasions, and > we haven't seen it recently. FWIW, my logs on mrochek.com (my home domain) show around 35,000 relay attempts during the past 6 months. This number is almost certainly much too low, in that I have various other blocks in place that may stop relay attempts before they get to the "don't allow relaying" rule. A cursory examination of the logs shows that most of the destination addresses are ones I've never heard of. But there are also a fair number of addresses I recognize as IETF people. Sure looks like somebody is tracking sender-recipient pairs off of mailing list mail. Mrochek.com probably qualifies as an obscure domain. > What sort of mail volume to you handle? 2000-4000 attempts isn't a lot > for large volume domain handling millions of messages per day. Overall traffic is about 500 legit messages a day and a highly variable amount of spam, but rarely less than a thousand spams and viruses a day. I don't think I'll be making my home system an open relay any time soon... Ned _______________________________________________ Ietf@xxxxxxxx https://www1.ietf.org/mailman/listinfo/ietf