Forgot to mention, but another point would be to avoid US based services. That excludes zoho.
Protonmail is definitely on the shortlist, what didn't convince me was a) not being sure how future-proof it is and b) their pricing table (limiting for labels used? emails sent a day? not that I'd exceed those values, but it sends wrong signals).
ProtonMail's mission is to keep your emails secure and they are relentlessly working to enforce and evolve this goal.
Giving the history of the team, coming from CERN and highly educated in MIT, Harvard and Stanford, I would not bet for a better company in the encryption space to survive better than them.
I don't understand your point related the pricing table. They are 100% community backed, started from a crowdfunding and they are surviving in an industry where email is considered free due to the other players in the market making profits with ads and data exploitation. It's normal for PM to limit the free account because it's based on a freemium model. The limitations, however, do not affect your experience and they offer you the same quality of security as the paid accounts.
Which in my opinion is pretty sweet. You should just check it out and see how it "feels" :) I pay for it but this is my choice because I support the mission and I want them to succeed.
