Explanation/Reference:
Explanation:
Note:
* Exchange 2013 Unified Messaging offers administrators:
/A complete voice mail system
Unified Messaging offers a complete voice mail solution using a single store, transport, and directory infrastructure. The store is provided by a Mailbox server and forwarding of incoming calls from a VoIP gateway or IP PBX is handled by a Client Access server. All email and voice mail messages can be managed from a single management point, using a single administration interface and tool set.
/An Exchange security model
The Microsoft Exchange Unified Messaging service on a Mailbox server and the Microsoft Exchange Unified Messaging Call Router service on a Client Access server run as a single Exchange server account.
Consolidation
* The client access server (CAS) is a server role that handles all client connections to Exchange Server
2010 and Exchange 2013. The CAS supports all client connections to Exchange Server from Microsoft Outlook and Outlook Web App, as well as ActiveSync applications. The CAS also provides access to free/ busy data in Exchange calendars.
The CAS is one of five server roles in Exchange Server 2007 and Exchange 2010, and one of two server roles in Exchange Server 2013. It must be installed in every Exchange Server organization and on every Active Directory (AD) site that has the Exchange mailbox server role installed.