1) Go to Run and type regedit
2) Go to:
\HKEY_LOCAL_MACHINE\SOFTWARE\MICROSOFT\EXCHANGE\CLIENT\OPTIONS registry key.
3) Right click options and add new DWORD VALUE (data type is REG_DWORD) and then right click and rename to DumpsterAlwaysOn. It is case sensitive.
4) Then right click and modify the value to 1 to turn the Recover Deleted Items menu choice on for all folders or enter 0 to turn it off.
5) Then go to Outlook , choose "Recover deleted items" option from the Tools
Menu to get back your "permanently deleted" mails!