What is the best mailbox overall?

Privacy/encryption is a top priority

Large Gmail archive needs migrating over. If possible, I'd need to receive emails sent to my Gmail account (even if I can't answer them from that Google email adress).

I recently switched from Gmail to Proton but I'm already looking to switch again.

I just want a mailbox that's safe and nice. Much like Ente really. I tried Tuta because they are "friends" but I only saw negative feedback...

EDIT: I choose mailbox.org!