After you migrated to Microsoft 365 Exchange, if the following error message appears when you open Outlook, please follow the steps below to update the Registry key.
- Close Outlook.
- Right-click here, select Save Link As..., and save the file to your desktop.
- Double-click the SignInOption0.reg on your desktop
- Click Run.
- Click Yes to User Account Control prompt.
- Click Yes.
- Click OK.