Since updating to IOS 10 my IPad 4 email crashes

Since updating to IOS 10 my IPad 4 email crashes. Apple has no answers. I trouble shot all my emails, uninstalled all accounts. Restored my iPad with iCloud backup. That didn't work. Then did a restore back to a new iPad then set up emails again and still emails crashed. Sent diagnostics to Apple who told me my battery sent a red flag. Now I see what they mean. My battery doesn't hold a charge now either.... so happy I upgraded to IOS 10 ... not... what does anyone think of this and has this been happening to anyone else? I don't want to trade in and pay $400 for a refurbed Ipad4 with all the new versions out there.

Any ideas ar appreciated. Thank,

BH