Best solution for iCloud mail on android but... ... An absolute data and battery hog on mobile. Had real battery and data issues: battery would barely last half a day and found K9 was the culprit. Found this out through a warning from network that I'd used almost all my monthly data limit and K9 had used over 3GB background data in a week  without any significant emailing! Solution was to disable background data for this app which means it won't do push email on mobile  but this is a small price to pay to have the phone behave. Sort it out  please.
August 10 2016