Accept it in harbor, send a new notification that it can be fetched after paying a processing fee (which includes the price of three previous notification). It

Accept it in harbor, send a new notification that it can be fetched after paying a processing fee (which includes the price of three previous notification). It's not like that isn't already done all over the place. It's not like that would happen often. They'd quickly adapt and start charging more for sending, making it a non-issue most of the time