I wanna get away from "free" email, but I think it requires a more full blown solution, something which offers a client with the polish of gmail.com along with it's excellent spam detection/protection, that can be self hosted on any random computer/server (using docker, or similar) that is very nearly plug and play.
Unfortunately, such a project would need to be OSS, with a consulting-type income structure, but the big companies that would be willing to pay for such a thing all use O365, and would never be willing to try something not nearly as proven.