[Spambayes] Use for gray area in scoring range

[Guido van Rossum]

Yesterday I said I didn't think there was much use for a gray area in
the scoring range, where messages scoring somewhere in the middle
would have to be manually inspected.  I think I'm going to revert that
opinion, at least with the Gary Robinson formula.

It would be handy to have this if you're trying to tweak the cutoff.
You don't want the cutoff too low, or it'll give you too many false
negatives.  But even stronger you don't want it too high, or it'll
give too many false positives.  Specifying a gray area gives you a
useful tool to see if you have set your cutoff right.

--Guido van Rossum (home page: http://www.python.org/~guido/)