[Spambayes] train on blank spam messages

[Ryan Malayter]

[Kenny Pitt]
> This is an option that is disabled by default, but you can enable it
> easily enough.  If you're using the Outlook plugin, you'll need to
> create a file name "default_bayes_customize.ini" in your 
> "Documents and
> Settings\username\Application Data\SpamBayes" directory.  In the file,
> insert the following 2 lines:
> 
> [Tokenizer]
> mine_received_headers:True

Is this option off by default because it did not provide a net gain for
most corpora? Or is it still experimental?