I have an HTC One M8 and am using the stock launcher and am not rooted.
I keep getting the error Unfortunately, Mail has stopped. when I try opening the stock HTC mail app.
I have gone into the App Info for the mail app and tried to "Clear cache" but it doesn't look like it's doing anything.
I have also gone to Settings>Accounts & Sync>Exchange ActiveSync and unchecked Mail in the account that is using it.
I have also tried rebooting my phone.
Any other tips or advice aside from basically wiping the phone?