Hi, John.

>It sounds great! One question: is it submitting the whole e-mail message to spamnet's server for heuristics, or just checking sender addresses?

It is an heuristic mechanism. Of course, sender addresses are useless because spammers keep changing them. They extract what they call SPAM-dna from every submitted message. Some sort of pattern like the one you or me apply to detect this: the text, the layout, nasty tricks like serialized-GIFs, etc.

But it is not enough for you to mark a message as SPAM for the service to filter it. Instead, they weight how many people identify the same Message (same dna, although slight variations may exist), and they start filtering it out beyond some threshold.

The key here is obviously the network effect. As more people use it, it becomes exponencially more and more efficient.

Of course this is the concept, and they keep the whole algorithm secret, but it works perfectly well. You can read more details in their WebSite.

By the way, I had to thank Garret Fitzgerald for pointing me to this tool in the first place. I read about it in his signature (not sure if here or in an email).

The link is: http://www.cloudmark.com/

See you,