I’m really digging the Spark for Mac email app. It has some nice customization and third-party integration options, while keeping things clean and simple. I emailed them about my pet peeve of email apps including a non-removable Send button on the MacBook Pro Touch Bar (see previous Outlook gripe), and they shipped an update with a configuration option two days later! I wouldn’t expect that for every feature request, but I was really delighted with the responsiveness, particularly given that it’s a free app. Check it out.