[Spambayes] (non-)spam count would go negative!

[Meyer, Tony]

> Unless I'm missing something, a further problem is that 
> spammers could add this header to subvert the training
> process. Right?

I thought that there was code to get rid of these, but I can't find it.
If there isn't, then yes this could happen.  However:
  * It's only training, not classification, since the classification
headers are definitely ignored if already present.
  * The new message module does remove all existing spambayes headers,
so all the apps that use that would be safe.  At the moment this is only
imapfilter (unless also pop3proxy; I can't recall), but the idea is that
all apps will use it eventually.  (Although some, like the Outlook
plugin, don't touch the headers, so won't use that bit).

=Tony Meyer