Email has never had such a thing and likely never will, now that we understand the deep perils of spam. Mastodon has a problem email doesn't have because email doesn't want it.

A better example might be to look to email's "sister" NNTP, which hardly anyone uses these days because no one could figure out the spam problem. People switched to privately maintained mailing lists and web forum software because it had fewer spaces for a tragedy of the commons.