True...I hadn't thought about BCC, because most mail I get isn't.  It's a simple enough fix to add that as well into the same filtering scheme, and you should solve the potential problem.  I have several other filters, which are ordered in such a way that application will 99.9% of the time not delete a legitimate mail.  For geocaching, there is a special filter just for it, including mail header info as well as subject.
 
Brian
Team A.I.
I haven't lost my mind.  It's backed up on disk somewhere.