What it does is compare each email to a list of known spam. That’s nothing new. However, if a spam does get through, then you hit the “Block” button, and it deletes the spam and sends it to the list so it will block it for everyone else. There are about 400,000 users, and they’re all identifiying spam and keeping this list updated.
I can only think of three things that might be issues with this system:
1. It actually downloads the email to Outlook and handles it there, instead of handling it at the server level. So I sometimes get a new mail icon, then get to my Inbox just in time to see the email vanish to the Spam folder.
2. The system sends information to a central database, which may make some people icky about privacy. It doesn’t bother me.
3. There’s a chance that someone, somewhere could block a newsletter or something that you actually want to get. However, this hasn’t happened to any of my newsletters, and nothing gets deleted — it all goes to a Spam folder that I can review. In the latest release, if you cancel a block on something twice, then that sender is added to your Friends list and is not filtered.
I’m been using SpamNet for three days: only ONE spam has gotten through, and NO legitimate emails have been flagged as spam. Seems to work great.