There are basically two good, actively developed FOSS email apps for Android: K-9 and FairEmail. Development of FairEmail almost ceased recently, as the develop

There are basically two good, actively developed FOSS email apps for Android: K-9 and FairEmail. Development of FairEmail almost ceased recently, as the developer was having issues with Google Play and no longer felt it was worth his time to work on the app. Thankfully he ultimately decided to continue development. I remember last year there was also a big campaign to get more donations for K-9 as the developers badly needed more resources to continue development. The category of FOSS email apps may not be dying, but it is small, and never far away from death. Having a large, established project with decent resources backing K-9 is definitely a good thing for the health of the category IMO. Personally I use FairEmail and hope that it will continue to thrive as well.