I go from Gmail, but cannot backup account everytime I reset or change custom rom so, tried now:
K9, fairmail, spark, blumail, acquamail, outlook and maybe also others.
I’m here becouse k9 is simplest than others, and just work.
The only issue (a missed feature) is schedule email (eg send tomorrow or send at specific date/time). Feature present in Gmail, fairmail, spark (not in outlook, very appreciated also this).
Hope can be added asap