One other comment: a rule for this should have a near-zero false-positive rate.
The punctuation in the tag (particularly the hyphen) is deliberate, to
prevent it matching ordinary English language text, and since it has
to occur at the beginning of the subject, 'Re:' and 'Fwd:' tags and
the like would prevent a rule from matching.
I'm rather pleasantly surprized that the FTC has (purposefully, it
appears) come up with a label that is designed to be useful to spam
filters...
-roy
