Great article. I've started hosting my own email server but I still use protonmail for some specific use-cases (emailing to people as my domain often goes straight to spam).
I actually didn't know that protonmail uses PGP for all emails regardless of if they're also using protonmail? I always assumed that it requires both users to use protonmail but it makes sense that a CA handles the public keys.
In the end I'll always trust the people who helped create CERN over the ones who created chrome ;)