After deploying Microsoft patches to my Exchange Server I started receiving the following Event on my Cisco Unity server:

Warning – Event ID: 29021 Source: CiscoUnity_AvWm: A MAPI function call to the Microsoft Exchange server took xxxxxx milliseconds, which exceeds the system threshold of 5000 milliseconds. The most likely causes are an overloaded Exchange server or poor network connectivity to the Exchange server. This is likely to affect the operation of the Cisco Unity server in a number of ways, including slow response or delays during phone calls, ports getting stuck or not answering calls, and Unity failover if a secondary server is active.

To troubleshoot this problem, enable all AvWM micro traces using the Cisco Unity Diagnosic Tool (UDT), and investigate the Exchange server for high system load and other indications that maintainance is required. For more information, please consult the Troubleshooting Guide For Cisco Unity with Microsoft Exchange.

Technical Details:
Method IMAPIT able:QueryRows (0×00000000)
Exchange Server: SERVER
Outstanding Server MAPI Requests:0
Parent Process: AvCsMgr.exe