That exact string occurs in a Vade Security header, X-ME-VSCause, added by Fastmail on a completely unrelated legitimate email I received.I think it's more like an obfuscated information header for Vade's own use.
I guess I'm not surprised. I would say then that it is a useless header as a spam or scam marker. Personally I'll stick with the easy method of a subject rule looking for the offending password, or hopefully ex-password.
Loren
