I find that all the spam that I get comes from 'yahoo.com' or 'hotmail.com' or a couple of other domains. As I do not know anyone whose e-mail address includes any of these domains I use an e-mail client that will automatically delete all e-mail from these domains without downloading it from the server, something very useful if the e-mail might have a virus.
The e-mail client that does this is called PocoMail (www.pocomail.com) which is shareware. There is another e-mail client that can be made to do this which is called Calypso and is freeware and is available from Rose City Software (can't remember the exact address)