Recovering deleted messages and mailboxes from backup media (Ex2K3)
http://searchexchange.techtarget.com/originalContent/0,289142,sid43_gci969555,00.html
Making a permanent delete temporary: Restoring a Deleted Exchange Object (Ex5.5)
http://www.microsoft.com/technet/prodtechnol/exchange/55/support/restorin.mspx
How to recover items that have been hard deleted in Outlook
http://support.microsoft.com/kb/246153