You run Microsoft Outlook 2016, and when you open Mail in Control Panel and then click Add on the Data File tab, you may receive this error message:
An unknown error occurred, error code: 0x8000ffff
This is a known limitation in Outlook 2016.
To work around this issue, add the data file in Account Settings in Outlook 2016 by following these steps.
- Open Outlook 2016.
- On the File tab click Account Settings, and then click Account Settings.
- On the Data Files tab, click Add.
- Add the data file as needed, and then click OK.
- Click Close on the Account Settings window.