On Mon, 22 Mar 2004, Michael Menefee wrote: > This just seems odd to me that the secondary MX record would receive a much > higher volume of spam and wondered of anyone else was seeing this and if > there was an explanation. BTW, for the 3 or so customers I'm referring to, I > process about 300,000 messages per day. The fallback box processes about > 70,000 per day, with about 68,000 or more being caught as SPAM
I read something about this a while back. A guy noticed something similar and did some investigative work on the matter. IIRC he added a non-existant tertiary MX to the domains in question. It was his belief that many spammer automatically jump to the last MX for spam delivery (based on the reasons in the other replies you received). He believed no legitimate mail should ever be sent to his highest MX when the lower MXs were still available and that if for some unbelievable reason his lower MXs really did go down, he would bring them back online before the sending machine dumped the message from its queue (since the highest MX didn't respond when contacted). He showed some very impressive numbers from his results. The amount of spam his secondary received dropped to near nill and his primary remained about the same as it had been with the secondary in place. I wish I could find his writeup about that now though. Justin
