Article ID: 981602 - View products that this article applies to.
In a mixed Microsoft Exchange Server 2007 and Microsoft Exchange Server 2003 environment, an Exchange Server 2007 Client Access Server (CAS) server handles the proxy requests for Exchange Server 2003 servers. After you upgrade an Exchange Server 2007 CAS server to Exchange Server 2007 Service Pack (SP2), you may frequently receive the following event in the Application log on the Exchange Server 2007 CAS server:
Event ID: 4999
This issue occurs because certain operations on the Exchange Server 2007 server check the site related attribute from Exchange Server 2003 servers. However, this attribute is not provided and Exchange Server 2007 does not handle the null response well.
To resolve this problem, install the following update rollup:
(https://support.microsoft.com/kb/2407025/ )Description of Update Rollup 2 for Exchange Server 2007 Service Pack 3
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
Article ID: 981602 - Last Review: December 14, 2010 - Revision: 2.0