Yahoo have now introduced a spam filter to their newsgroups. The daft thing is that not only is it having loads of false positives, it actually still sends you the email, but includes the spam email as an attachment. The only way this really helps is that it stops you accidentally opening spam messages containing web bugs to verify your email address. It also puts [spam] at the front of the subject (and an x-header line) so that you could put a filter on it. However with no way to whitelist or blacklist senders or any obvious means of training the spam engine its going to be more hassle than its worth.