Glen Eustace wrote:
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.
I haven't heard of people using this for the primary MX, and I'm not sure that doing so classifies you as a good net citizen (despite the "it's only 2 packets" argument), however... Putting in a non-functioning low priority MX record is a trick that's been around for a while, and seems to have good results. As others have stated many spam programs go straight to the lowest priority MX record in order to (possibly) avoid anti-spam software, and most will not even try any other MXes, even if the lowest fails. The difference between this and using it as the highest priority MX is that the incidence of legitimate mail using the lowest priority MX is somewhere between low and very, very low (depending on your network, etc). As for the primary, how long until it hits the blogs/press/etc that company X's primary mail server has been down for the past 3 months! ("When contacted the company said 'yeah, we know - we like it that way!'") Scott.