I have been using Outlook for the longest time and have tried FairEmail a couple of times and simply deleted it. Tried sticking through it for about a month and I'll be sticking with it for a good long time now :)
Edison. I use it on my Pixel, iPhone, and iPad. It has some more advanced features I don't use, it just has a simple, straightforward UI on iOS and Android and doesn't hassle me too much about upgrading to paid features.