I've been using Migadu without trouble. I used Protonmail before, but I didn't like the hoops I had to jump through if I wanted to use POP3/IMAP. They do have a

I've been using Migadu without trouble. I used Protonmail before, but I didn't like the hoops I had to jump through if I wanted to use POP3/IMAP. They do have a bridge daemon thing where you can sign into protonmail and it exposes POP3/IMAP locally but it's not available for phone OSes. I could set up a VPN or something, but that's more hoops than I wanted to jump through.