I built an email-powered social network called Uhuro (https://uhuro.com/). I guess it could also be used as a social listserve platform.

Email addresses work like APIs. For instance you can send emails to join@uhuro.com to join the social network or quit@uhuro.com to quit. Other email API addresses include:

- invite@uhuro.com = invites friends and family to join

- help@uhuro.com = Replies with the instructions

- follow@uhuro.com / unfollow@ = Follows or unfollows CC'ed users

- followers@uhuro.com = Replies with all users following you

- post@uhuro.com = Sends your email message to all of your followers.

Here's more information on how it works - https://uhuro.com/how.html