Tim Price wrote:
We use nolisting, greylisting and spamassassin.
When we implemented greylisting we found that our processed message load dropped from ~40,000 messages per day to ~20,000 messages per day. A while later we implemented nolisting and our greylisting load dropped by virtually the same amount. I haven't done too much log trolling because i'm lazy but looking at the stats for the last week tell the following story:
Total Messages Processed: 146373 Total Message Size: 2445MB Spam Messages Identified: 89108 (61%) Spam Data Volume: 552MB (26%)
AFAIK greylisting and nolisting do work as our spam volume percentages were closer to 95% beforehand.
Thanks Tim. A number of people it would seem have not read the theory behind nolisting and seem to have assumed that it will increase network activity and traffic. Provided that the non-functional MX sends a TCP reset, this is not the case. There is a single additional SYN packet and the corresponding RST from the fake MX. Running TCP dump on the fake primary MX and the real one indicated that there is almost no delay between the RST and the next SYN to the real MX. In our case we are using the Spamhaus Zen RBL -> Grey Listing -> checking valid recipients -> Spamassassin/ClamAV and last month blocked over 9 million messages, more than 98% of all inbound. Of that 98%, the RBL blocked about 98% of them. Adding nolisting simple means less DNS lookups with no other penalty that I have been able to determine. Agreed, it does NOT address the mail being sent directly to our secondary MX but there is still a lot of primary MX only SPAM so, IMHO, it is worth doing and does have a positive effect. -- =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- Glen and Rosanne Eustace GodZone Internet Services, a division of AGRE Enterprises Ltd. P.O. Box 8020, Palmerston North, New Zealand 4446. Ph: +64 6 357 8168, Fax +64 6 357 8165, Mob: +64 21 424 015 http://www.godzone.net.nz "A Ministry specialising in providing low-cost Internet Services to NZ Christian Churches, Ministries and Organisations."