When using Outlook 2016 with Exchange Server 2010, you may be prompted repeatedly for your credentials, even though you will be able to use Outlook without interruption.
To repair the issue, a registry entry is needed to prevent Outlook from forcing an Autodiscover lookup to Office 365 instead of local Exchange.
- Open the registry editor by clicking Start > type regedit in the start search
- Right Click and Run as Administrator
- Navigate to HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\AutoDiscover
- Create a new DWORD entry called ExcludeExplicitO365Endpoint with a value of 1
- Close and re-open Outlook. In some cases, you may need to restart the computer, but in my testing I did not.