Going to show my privilege here and say Superhuman. It’s expensive as hell, but if you’re like me and email is a major part of your job, it may be worth it. I can get the gmail web client to do about 90% of what Superhuman does, though. So for an economical version, perhaps look up a guide on how to setup and use the Gmail web interface with nothing but a keyboard. In my experience, taking the time to learn how to navigate your inbox in this way pays dividends down the road. Good luck!