[EmanueleAina]

As I see it, unless you can guarantee that you give zero false positives (which, knowing how certain users compose their mail, is arguably impossible) you still have to do it.

Also I suppose that the false positive/negative rate can only be given on a well defined corpus, I'm not sure there is one that is a good representation of the current and future spam trends, so in the end giving those numbers could be very misleading.