After trying Airmail, and becoming frustrated with Apple Mail, i finally found the right fit. Besides being crazy fast and responsive always. A few cool features it does that I always wished the others would do. When I turn off "Load Remote Content" I can then whitelist people I want that on for! Built in encryption. Built by an indie developer and a reasonable price for advanced features, no subscription! Honestly the only feature I am missing is the ability to have multiple signatures and pick the one I want (there is per account) but sometimes from the same account i might want a personal and formal style signature. But that is very minor great job overall.

https://canarymail.io/