Exchange Unified Messaging Architecture

The Unified Messaging server role includes connections to different components, such as the Client Access or Mailbox server roles, and also to IP PBX or IP gateways, as shown in Figure 1.

 

Figure 1: Unified Messaging architecture

Generally, the UM server role communicates to an IP PBX or to a PBX using an IP gateway with the Voice over IP protocols (VoIP), Session Initiation Protocol (SIP), and Real-time Transport Protocol (RTP).

The UM server role uses MAPI protocol to communicate with Client Access and Mailbox server roles, and SMTP protocol to send voice mail messages to the destination mailbox viathe Hub Transport server. For Outlook Voice Access the UM server role accesses the mailbox using MAPI protocol to have full access to all items in the mailbox such as messages or contacts.

The Unified Messaging role no longer supports an inbound fax like Exchange 2007 UM. However, UM retains fax configuration properties, and continues to be sensitive to fax tones on calls that it answers and forwards these calls to a partner fax solution. The received fax messages look essentially the same as those created by Exchange 2007 UM, and will appear as a fax when the user is UM-enabled.

The communication to the other Exchange roles—namely the Hub Transport, the Mailbox, and Client Access Server roles—uses MAPI connections to perform tasks such as opening a mailbox for OVA or sending a voice mail message when the call has ended.