Tutanota is pretty good though they feel entitled to send marketing/commercial messages to their customers with no ability to opt out.
I've been using Fastmail with my own domain for a few years and never had a problem. Web and mobile apps are great.
I've set up IMAP syncing with my main Gmail so that it also acts as a backup. Eventually I'll ditch my Gmail for good, but sadly I'm not there yet.
maybe Gmail isn't that bad... Yes you may be targeted with ads and what else brings revenue to Google. Yes you could expect that law enforcements may scan/seize your inbox but if you're kind of fine with either of these, I certainly trust more Google than anything else when it comes to protect against real hackers/unauthorized access