Learning Backscatter

[Matt Garretson]

In addition to what David and Pavel have mentioned, I'll
add that if you train on backscatter as spam, you might
also want to train on some legitimate bounces as ham, 
otherwise your scoring might be skewed against DSNs of 
all sorts.  This might not be a problem for you... just 
something to consider.

Personally I find that, overall, bounces (both legit and 
backscatter) tend to defy Bayesian training, so I have
some bizarre custom MIMEdefang/SpamAssassin rules in place 
to handle bounces.  Of course, the bogofilter score weighs 
heavily in these rules.

-Matt