https://docs.microsoft.com/en-us/outlook/troubleshoot/data-files/cannot-change-the-location-of-ost-file


Workaround Method 2 - Set the ForceOSTPath registry entry to change the location of the .ost file

 Note

The value of the ForceOSTPath registry entry only works for a new Outlook profile.

 Important

This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, see How to back up and restore the registry in Windows.

To set the ForceOSTPath registry entry in order to change the location of the .ost file, follow these steps:

  1. Select Start, select Run, type regedit in the Open box, and then select OK.

  2. Locate and then select the registry subkey: HKEY_CURRENT_USER\Software\Microsoft\Office\xx.0\Outlook

     Note

    The xx.0 placeholder represents your version of Office (16.0 = Office 2016, Office 365, Office 2019, or Office LTSC 2021, 15.0 = Office 2013).

  3. Right-click Outlook, select New, and then select Expandable String Value.

  4. Type ForceOSTPath, and then press Enter.

  5. Right-click ForceOSTPath, and then select Modify.

  6. In the Value data box, type the full path of where you want to store the .ost file (such as D:\MyOST), and then select OK.

  7. On the File menu, select Exit to exit Registry Editor.