I suggest we find a way to close a mail thread. Obviously we can't stop people from sending mails, but, like when a mod sees the topic has been juiced out, he closes the topic which practically means:
if mailman sees mails being sent to a topic closed by a mod, it does not relay it to the list.
It is normally difficult to say when a topic has been juiced out (the essentials have been said, with no new inputs). One might close the topic prematuraly. So, a time-based automatic closing might be better. Example: After 5 days, a topic is closed. A mod can extend the closing though.