I have been using FairEmail recently. It's excellent. Easy to setup, easy to use, lots of options to go deeper.
Considering the setup, you can use OAuth for the big providers which is excellent for less tech savy people.
There is ample help in the form of messages provided in contextual menus in the app if one was in need. As well as many information button that point directly to the very complete Github FAQ.
All around a great app, for now. Might report back in a few months.