Usenet groups are superior version of the same thing, they still exist, and no one cares.
Technologically it is a solved problem. It's not very helpful against addiction (one can just click send and receive more often) or large volume of messages (spam killed usenet).
I have already seen software restraints to emulate the 90s - "you may only send messages once a day" experimental offline-first-lifestyle mailing client at hackernews. If that can do any good is anyone's guess.