Exchange Server Role Architecture

           In old version of Exchange Server, there were five server roles hosting various functionalities, including:
• Mailbox Server role
• Client Access role
• Hub Transport role
• Edge Transport role
• Unified Messaging role
           But In Exchange Server 2013, the number of server roles is greatly reduced, to only these two roles:
• Mailbox Server role
• Client Access server role
           All additional roles, except the Edge Transport role (which does not exist in Exchange Server 2013), are integrated within these two roles.