Loved this app but it suddenly started draining both data and battery. First warning was a text from my operator saying that I'd used 6GB mobile data in a couple of weeks last summer. Checked the phone and it was almost all down to K9. Disabled background data — hardly ideal — but I was prepared to give the program another chance. Final straw happened a few days ago when I experienced serious internet connectivity problems  only to discover that K9 Mail had used over 60GB of wifi data over the previous month. At the risk of stating the obvious  this is insane! Having persevered with this for years  I've now given up  uninstalled and gained about 3 hours battery life per day. Should be removed from the Play Store.
December 30 2016