A few months ago I started using Osiris as my web hosting service partly because they provide Postini spam and virus filtering. Now that our new nwfolk.com email addresses have been thoroughly found by spammers, I find that the Postini service works well. At first it classified some legitimate mail as spam, but it lets me whitelist those senders. Lately it's been 100% effective in blocking spam and viruses. Your mileage may vary, but it works for me.