Protonmail is pretty great and has good mobile support if you're into that. It also decrypts all emails locally on your device, using two passwords. One to get access to the encrypted emails and download them when you login. The other to decrypt the emails on your device.
This is a pretty good system, especially when you provide you with 2048 (I think) bit encryption for free. Combine that with PGP encryption on the email contents itself and you're good to go selling nukes to Albanian Mafia heads.