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

[Alessandro Vesely]

Seth wrote:
> 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.

Yes! Opt-in info has to be stored at the recipient's server, in 
addition to the sender's:

The sender obviously needs the recipient's address; but cannot provide 
a standard mechanism for unsubscribing, since there isn't one.

The recipient's ESP could use the knowledge that a message belongs to 
a subscribed list in a number of useful ways (e.g. to suppress auto 
responders.) Semantically, that would validate the sender's opt-in 
record. However, notifying opt-ins is not standardized either.

Thus, I think there is a whole protocol that we're missing. Can't we 
just specify it in an RFC and see if it flies?