If you are using gmail, yahoo mail or iCloud, consider making a change to protonmail.com. A basic account is free, and you’ll avoid filters, censorship and privacy issues.
Great article here from Dr Malone with some recommendations. Happy Paralleling!
Unlike Frank I don't have problems with Tutanota. They use in-house encryption. Others are here;
https://prxbx.com/email/
or here;
https://prism-break.org/en/all/ (scroll down to email clients)
Agree that everyone should get off gmail, yahoo, apple. The first two especially.
You need to realize though that the Americans (amongst others) have been very good at breaking encryption for a while. And Swiss, Swedish and German providers are not out of their influence.