Recovery Shift Delete mails
How to recover shift deleted mails in Outlook
First go to Run and type Regedit
Go To:\HKEY_LOCAL_MACHINE\SOFTWARE\MICROSOFT\EXCHANGE\CLIENT\OPTIONS registry key.
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.
right click and modify and make the value 1 to turn the Recover Deleted Items menu choice on for all folders or enter 0 to turn it off.
Log off and restart Outlook, in case you are already logged on. Choose "Recover deleted items" option from the Tools Menu to get back your "permanently deleted" mails!
This is taken from Microsoft website