For the sake of discussion, let's say we had 20 different classifications and someone suggests adding one for hobbyists who may have one or two servers for family and friends and likely the family and friends businesses. My question: How is this source of email different than any other? If you are saying that their servers are operated on a cable or DSL with a residential rDNS, then I can see a reason to have a classification for them. One might ask, as a spammer, then shall I just put in a classification of "home hobbyist" for 1000 zombie home cable users I've got a trojan mailer on? Self-classification of course isn't necessarily trustable but in combination with other tests still seems useful. In the case of the zombie spammer above, I would look at the envelope-from domain. Is it new? etc.