[Spambayes] better Received header tokens

[Tim Peters]

[Tim]
> For another, about the only spam I see rate unsure anymore is stuff
> that leaks thru SpamAssassin via python.org.  spambayes *usually*
> wouldn't have any trouble with such spam on its own, but there are
> a dozen header clues all effectively saying "this came from
> python.org" ....

[Skip Montanaro]
> That's correct when considering the rather narrow Python email
> universe, but I suspect most people live in a somewhat more diverse
> electronic world than that, so the python.org effect won't be quite as
> strong in the normal case.

It was an example of harmful correlation, by way of illustrating why a
strong indicator isn't necessarily a desirable indicator.  This particular
example applies pretty directly to any source from which a user rarely (but
not never) gets spam, and leaves clues about itself.