I realized Discourse allows to reply via e-mail quite good. Would it be possible to add some simple mailman-like UI and potentially use it as a replacement for current mailinglists? As a motivation I would see easier access to the history and a onboard price for newcomers or common public.
Seeing how Palemoon or Vivaldi work with the community, I think the Discourse forum would be great to promote and use even more as the central part for community/public communication backbone for Mozilla.