- Close the MS Outlook email client.
- Press the Windows + R button, type regedit, and then press Enter.
- Navigate through the following registry path: HKEY_CURRENT_USER\Software\Microsoft\Office\version number\Outlook.
- Right-click the Outlook sub key, point to New, and then click the Expandable String Value option.
- Specify ForceOSTPath. Press the Enter key.
- Right-click the newly-created ForceOSTPath. Click the Modify option.
- Specify OST file path for saving in the Value box. Click the OK button.
- Exit the registry editor.
https://www.nucleustechnologies.com/how-to/change-ost-location.html#:~:text=Navigate%20through%20the%20following%20registry,Press%20the%20Enter%20key.