I think I know the answer, bit maybe I'm missing something

Since proton only sends and receives encrypted emails to other proton accounts, that means that when you get or send an email to someone else, they have to send / receive unencrypted and there is no way for us to verify what they are doing. Right?

Also if most accounts are google Microsoft, they still get 90% of my emails. By switching to proton I think I've gained nothing, while losing convenience , added another trust point, and having two different companies have my data instead of just one

Proton drive, calendar and VPN I think are fine

Sorry for the poor syntax. I'm at work working on email related things, and this topic kept distracting me. I might correct it later