Exchange architecture revisions: Exchange 2007 and 2010 are split into five roles, mainly to address issues like CPU performance, which would suffer if Exchange were running as one monolithic application. But Microsoft has made progress on the performance side, so Exchange 2013 now has just two roles: Client Access server role, Mailbox server role including the Edge server role. The Mailbox server role includes all the typical server components (including unified messaging), and the Client Access server role handles all the authentication, redirection and proxy services.