1. In Outlook 2010, click on File > Open > Import.
   
   
2. Now select Export to a File and click Next.
   
   
3. Now select Outlook data file (.pst) and click Next.
   
   
4. Select the uppermost folder in your mailbox tree, tick Include sub-folders and click Next.
   
   
5. Now choose a location on your PC to save the backup file, and click Finish.