I've been using SpamNet (www.cloudmark.com) for some time now, and it's been working fairly well.  However, I just checked my spam folder, and I found all kinds of things in there that aren't spam.  Regular mailing list entries, bug reports from customers, and more.  Looks like I might have to start scanning the Spam folder every day.  Sigh...  Email is becoming virtually unusable with this virus and spam.