As a messaging system that is widely used in both large corporations and small businesses, Microsoft Exchange Server has always been scalable in both directions. However, new demands on messaging—such as compliance, security, and disaster recovery—have created new challenges for delivering a messaging system that works great in small businesses and large enterprises alike. To rise to these new challenges, the architecture of Exchange Server 2007 has been updated to take advantage of 64-bit hardware and simplified administration and routing, and to enable an Exchange Server to host one or more server roles.