Assume that Exchange ActiveSync is enabled in a Microsoft Exchange Server 2010 Service Pack 2 (SP2) or Service Pack 3 (SP3) environment. Additionally, assume that ActiveSync devices use an AirSync protocol that is earlier than version 140. In this situation, the W3wp.exe process for the MSExchangeSyncAppPool application pool crashes.
This issue occurs because ActiveSync devices that use earlier versions of AirSync protocols generate invalid requests. This causes an unhandled exception. Then, the MSExchangeSyncAppPool application pool crashes.
To resolve this issue, install the following update rollup:
2866475 Description of Update Rollup 2 for Exchange Server 2010 SP3
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.