It’s not that it’s closed, it’s more that none of the exiting email protocols support a server which can’t read your email (as it’s all encrypted). They do offer Proton Bridge which you can run locally which will handle all the decryption and local mail clients can talk to that as the would any other mail server.

I don’t know off hand if it supports calendar syncing though.

It’s been a while since I’ve had to touch it too. But couldn’t Alice provide Charlie with both the plain text and her public key. Charlie could then encrypt the text and see it came out the same as blob Bob sent Alice?

Typically end to end encryption includes digital signing of the message so you can verify who the sender was.

Yeah, end to end encryption means its not possible for someone to intercept the message between person A and person B. Nothing stops person B then forwarding the message to person C to report it.

This was the tool I used. It worked great for me.

Set Immich up a couple weeks ago and I’m surprised how good it is. Their docs included a simple cli tool to bulk import all my Google photos. Mobile app is working great. I’m really impressed with the search too.