Here’s a thing that is not often said out loud about e-mail encryption, courtesy of Migadu:

"Email as we know it and encryption are incompatible. If someone is telling you otherwise, they are not to be trusted.

Email is built on top of plain text protocols and messages flow in plain text. If you encrypt, you cannot scan for spam or viruses, index messages for searching or recover messages when a password gets lost. Not to mention the usability issues of changing passwords / encryption keys.

This cannot be fixed, at least not any time soon without breaking the protocols on which email relies.’

[…]

We know some email providers automatically encrypt messages as they arrive using users' public keys. That sounds exciting but in practice it does not really prevent the provider from accessing the mails. It only makes email less usable, less standard and more tied to that provider. What you gain in security you lose in portability and usability, and what we do not want for ourselves, we won’t be offering others either.”

https://www.migadu.com/procon/