Yesterday, I came across the concept of 'nolisting' as a technique for reducing the volume of inbound spam. It wasn't something I had previously come across so have done some reading on the topic. http://nolisting.org as a starting point. For such a simple technique, I was surprised by its impact. Simply speaking, the idea is to use a primary MX that doesn't listen on port 25 but simply rejects the connection. Well behaved MTAs will all try the secondary MX(es) and delivery will occur. Many spambots only try the primary so there is an immediately benefit, less inbound to check in other ways and a consequential increase in the available resources on the mail server(s). I set it up on one domain and behavior seems to be exactly as described. My reading suggests that there is no negative impact on legitimate mail and no noticeable additional latency in delivery as the switch from the primary to secondary on a reject is almost instantaneous. I was wondering whether anyone else has had any experience with this technique and if so whether the claim that it has no negative impact is true. Also, if people haven't heard of it, it may be something people might want to look at as another weapon in the anti-spam war. Glen.