It’s AirMail for me. I use this many years already and happy with it. I don’t like the subscription tho and lately nothing new is coming. It seems it’s more of a cash cow now for the developers. And sometimes strange behaviors, but still the one for me.
Oh, definitely don’t expect or want free. But charge me once. Don’t make me pay you in perpetuity. Then, go make more things and I’ll buy those too.
Adobe and CC made being beholden to a subscription for software the norm and I despise them for it. Luckily some fantastic alternatives were born from it.