I wrote this to Spamnet today. I still think their service is excellent. It could just be a little better.
I get about 3 false positives per week, mostly from mass mailers from companies I want to receive mail from (IE. Coldwater Creek, Pogo.com, Avantgo, NikonNet). I suspect that these false positives come from other Spamnet members that want to cancel their subscription to these mailers but not wanting to bother with unsubscribing.
Please make it more clear to Spamnet users that the “Block” button should only be used for spam and not to unsubscribe from legitimate mailers. Your tutorials don’t express this clearly enough.