I think it's dumb to filter for this as anything but a weight. I do exactly
the same thing as above often, it's a perfectly legitimate way to send
(solicited) mass mail with compact headers, and I don't expect to have
somebody's filter excoriate me for it. Spammers aren't the only ones whose
Filtering on this AFTER the normal recipies for list servers, etc.
is a better way. I'd think a recipe that take "junk" and "bulk"
as a weight along with this might be useful. It's a tricky one,
but I grab one SPAM message every couple of days with it.
I'm beginning to think it's not productive to send bounce messages
or Nag-O-Grams, so just filing these away for future reference may
be the best bet.