I'm getting this from our CAS Exchange Server
Event Log Module Status: 0
The Last Record Number of the eventlog type that current event entry belongs to: 0 # of duplicate events: 3
Source: MSExchange ActiveSync
Event ID: 1016
User (If Applicable): N/A
Event Description: Exchange ActiveSync has encountered repeated failures when it tries to access data on Mailbox server [MKVMMBX02.MK.LOCAL]. It will temporarily stop making requests to the Mailbox server for  seconds to reduce load on that server. This delay may occur if the Mailbox server is overloaded. If this event is logged frequently, review the Application log on this server and the Mailbox server noted above for other events that could indicate the root cause of performance problems.