Are you responsible for multiple exchange (e-mail) mailboxes? Tired of sent items not going into their corresponding sent-box? Here is the solution for Microsoft Outlook

Email that you send on behalf of someone is not saved in their Sent Items folder

From: http://support.microsoft.com/kb/2181579

This also works in newer versions of Outlook, just locate the appropriate registry key version.  Microsoft FixIt will also make the changes for you locally