I've used this for over 4 years without any problems  however since the latest update and Android 7 it constantly stops syncing! I've made no changes and have managed to get it syncing again by changing the poll frequency but without warning it stops again? I found K9 when my stock email failed to cut the grade and this problem has forced me back only to find the stock app on Samsung is much better  so sorry K9 you've dropped the ball and I've been forced to move on. The syncing issue is all over the internet forums so it doesn't look like much is being done to rectify the problem. I may be back one day but I suspect not soon.
February 26 2017