Exchange Server 2007 Out of Office (OOF)
The Out of Office (OOF) feature is commonly used by end-users to let other people know when they are not available to respond to e-mail. Exchange 2007 Out of Office capabilities such as scheduled OOF, different external and internal OOF messages and the ability to control what kind of OOF to send on a per-domain basis improves the experience for both end-users and for administrators.
Read more at source: http://msexchangeteam.com/archive/2006/10/06/429115.aspx
Ice Rocket : Exchange Server 2007, OOF, Outlook 2007