Highly recommend Fastmail. Fantastic server side search and web app (plus has calendar which is essential for an email app imo). There also is nothing holding you back from bringing your own mail client (that can actually interact with the server eg tagging). They also allow connecting to other accounts such as gmail letting you have a single inbox on Fastmail itself.

Favorite “hidden” feature is the ability to do sieve scripting which combined with wildcards and send from identities lets me auto sort emails by path. Eg apps-tech-hackernews@example.com. Also the standard account comes with 100 domains and are real easy to setup.

Been using it for a year now and I haven’t had a single issue. Also the pricing is very reasonable.