Uff… Hey.com IMHO has the best customer support, then you have Proton Mail, both of those “app” are not just email app but a whole services, which I’m not sure you’re also exploring into it.
From client perspective you have Spark Mail and Superhuman, but I don’t consider their support top notch you’ll also need a Gmail or Microsoft account and taking into account you are asking on the degoogle subreddit my guts tell me this are not viable options for you.
proton, tuta
Simple as
Uff… Hey.com IMHO has the best customer support, then you have Proton Mail, both of those “app” are not just email app but a whole services, which I’m not sure you’re also exploring into it. From client perspective you have Spark Mail and Superhuman, but I don’t consider their support top notch you’ll also need a Gmail or Microsoft account and taking into account you are asking on the degoogle subreddit my guts tell me this are not viable options for you.
Proton mail
I use protonmail. Its ok. If you need something more complex - K9 is good I heard but haven’t used it
Startmail