[Asrg] processing mailing list headers (was FeedBack loops)

[Seth]

Years back, I made a suggestion to insert the ISP into the loop so the
ISP _knows_ that the user opted in to a list.  That makes it easy for
the ISP to decide that "TIS" means "unsubscribe" (or even "Ask the
user if that was an oops").

Without the ISP knowing that the subscription is legitimate, the
message has to be reported the usual way.

Seth