Exchange 2007 was the first release of Exchange to include Unified Messaging (UM) and this was the first time many of our customers started considering replacing their existing voice mail systems with UM. As with any new technology, many have sent in questions or concerns regarding the legal implications of UM, and how to control the voice mail messages once they’re inside Exchange.

Read more at source: http://msexchangeteam.com/archive/2008/08/21/449657.aspx