I'm using Fastmail for my side hustle. It's okay. I find it has nowhere near the usability of Outlook, but I want to avoid Microsoft snooping.
I tried Proton Mail, but I couldn't get the services I wanted - every time I added X, Y was removed. And if I added Y back, something happened to X.
I don't want to manage my own email server because I want to spend that time and energy elsewhere. Plus, I would still have a bad user interface.
Any suggestions?