I'm receiving several large emails a day -- sometimes dozens -- from the W32.Mimail worm. While I don't much care from a security point of view, since I'm not running a platform that it targets, if I mark it as 'junk' (as often as I like) it still never gets 'learned' by Mozilla MailNews' spam filter and always gets through, despite having a very characteristic unobscufated opening paragraph (and then an attachment -- I don't know if the attachment is randomized). I think that the spam filter really should be able to 'learn' this spam.
*** This bug has been marked as a duplicate of 218942 ***
Ah, sorry for the double-report, bugzilla was taking so long that I resubmitted (with bonus spelling fix).