I would suggest you to go for manual techniques like Import & export.
Open MS Outlook & click File menu.
Select the “Import and Export” wizard.
Now click the “Export to a file” option and then click Next button.
Select Personal File Folder (.pst) and then click Next button.
Select items to be exported or Click on parent root and check the Include sub-folders option.
Browse and select the target folder for saving the email items.
Click the Finish button.
Hope this process works. If it doesn’t work, you may also checkout the EasyTechTools BLOG for more manual procedures.
How To Convert OST Files To PST
Hope this answer helps