Unified Messaging Technical Reference
Enable Exchange Server 2010 MWI integration with Interaction SIP Proxy
Customer Interaction Center, when configured as a Unified Messaging (UM) IP gateway on the Exchange Server, does not natively support delivery of Message Waiting Indicator (MWI) Notify messages to endpoints when a user receives or deletes a message from his or her mailbox.However, you can support MWI messages in this environment if you install Interaction SIP Proxy and do some configuration tasks.
You can configure Interaction SIP Proxy to route MWI Notify messages to SIP endpoints, such as IP telephones, and to route voice mail call setup messages between Exchange Server 2010 and the Customer Interaction Center server.
For more information, see the following: