Remove Corporate Email Account (Exchange ActiveSync®) - The all new HTC One® (M8)
Removing then re-adding your corporate email account (Exchange ActiveSync) often fixes login and not receiving email issues.
From a Home screen, navigate: Apps > Settings > Accounts & sync.
If Settings is unavailable, tap the Dropdown menu (located in the upper-left) then tap Alphabetical. If still unavailable, refer to Manage App Icons.