Well, where's the money in email? Services, right? The reason Twitter didn't go the same way as email is because it's centrally controlled and hostile to services, in my opinion.
I can think about at least a couple of services that do it out of sheer altruism or for political reasons (like Autistici or Riseup) and don't mine your content.
Degooglisons-internet [1] is an initiative (broader than just email) to promote free services without selling your data. It aims at giving easily deployable apps so more hosters can appear.
