Export
Click File in Outlook
Select Open & Export, then Import/Export (In Outlook 2010 is found under Open then Import)
Select Export to a file and click Next
Select Outlook Data File (.pst) and click Next
Select the folder labelled your email address (Tick Includes Subfolders) and click Next
Now click Browse and locate where you want the data file to be saved (Desktop is recommended) and Click Finish
You will be asked to enter a password, you don’t need to do this just click OK
Your mailbox will now start exporting (This may take a while depending on the size of the mailbox)
Import
Click File in Outlook
Select Open & Export, then Import/Export (In Outlook 2010 is found under Open then Import
Select Import from another program or file and click Next
Select Outlook Data File (.pst) and click Next
Now click Browse and locate were saved the data file and click Next
Finally, make sure Includes subfolders is ticked, Import into the same folder in: has your email address in the drop-down and click Finish