On a related topic, I wish someone would implement "user-encrypted-at-rest" to protect me from the provider getting breached.

I don't care so much for the transit, but I'm a bit worried about the fact that I have many years of emails stored in "plaintext" (citation makes because they probably use FDE and maybe other encryptions but they can still read everything) on the providers server.

I'm not worried about a malicious provider, but worries they might at some point make a mistake which allows them to be hacked.

If anyone knows any solutions for this that works in iOS/Mac I'd love to hear.

The only thing I've found on this is some research a few years ago with ideas how to do this; but I haven't seen any implementations of it. I've linked to it here: https://www.cs.columbia.edu/~koh/papers/koh-eurosys19-e3_eas...