I'll only tackle the two points in your comment nobody's seemed to bother with yet:

> There aren’t too many people capable of jumping through all the hoops

The people who would be willing to put effort into trying Eppie out, are the same that will put effort into setting up (what is nowadays the trivial task of) setting up a mail server. Guess which one they'll pick? Hint: It's the one which works with all the other mail servers on the planet.

> but yes, if you go as far as self-hosting your email, your data is under your control, not Google’s. The address though is still not yours.

If you mean in so much as the domain you've registered could be taken away from you, then, I guess? How likely is that? The bloody _piratebay.org_ is still up and running.