The problem is that it is not at all obvious to a member that unsubscribing from AHA spam also unsubscribes one from receiving NHC hotel notifications, especially when the registration itself is handled by a third party. I would not have known that a notification went out had I not been a member of this forum. Yet, I received notification that I was "in" as well as receiving my invoice from Altitude Tickets. That's why I am referring to this problem as an impedance mismatch.