I am planning to move out of Gmail, yes I know this is very late but better late then never. I tried proton mail, it's good and I don't know I amnot able to completely believe that they are good enough. So, seeking for experts opinion here.
Similar question from 3 months ago "Ask HN: Secure email provider" <a href="https://news.ycombinator.com/item?id=15112084" rel="nofollow">https://news.ycombinator.com/item?id=15112084</a> though it's more about security towards governments, not against the mail provider itself.