Microsoft introduced the Personal Archives with Exchange 2010. In earlier releases of the product, messages were archived using 3rd party utilities. In addition to eliminating the need for external archiving solutions, this new feature removed the necessity of PST files. Also, since the Exchange Archive is a mailbox, it’s capable of leveraging built-in replication and high availability features within Exchange.
With the introduction of Exchange 2007 came many new features and improvements that help to improve productivity and management: multiple server roles, a 64 bit architecture, built-in high availabilty features (LCR, CCR, SCR and SCC) and Messaging Records Management just to name a few. Another change you will notice is with Email Address Policies (EAPs) and Address Lists.