Deleted items in Microsoft Outlook that are stored in “Deleted Items Folder” start to pile up and take space after a while.
In order to remove them permanently everytime Outlook is closed :
1. Open Outlook 2010 and go to File > Options.
2. Select “Advanced” tab and in the “Outlook start and exit” section, enable the tick mark next to “Empty Deleted Items folder when exiting Outlook”. Click Ok when done.
3. So from now on,this will prompt a confirmation box regarding whether to keep or delete items in the Deleted Items folder whenever Outlook is closed.