Talking about Exchange Server 2007
There are a lot of new features in Exchange Server 2007 SP1 such as SCR (Standby Cluster Replication), Tools for Public Folders, IMAP and POP; IPv6 support, PST export and import and more..
Read more at source: http://msexchangeteam.com/archive/2007/02/23/435699.aspx
Ice Rocket : Exchange Server 2007 SP1