This article introduces an update for Microsoft Exchange Server 2010 Service Pack 1 (SP1). This update changes the cookie name of the cookie that is set by Microsoft Office Outlook from XSID=<GUID> to OutlookSession=<GUID>. This change lets Exchange Server 2010 SP1 support multiple Exchange Server 2010 Client Access servers in one datacenter. Therefore, Exchange Server 2010 SP1 support the remote archive feature.
To resolve this issue, install the following update rollup:
2529939 Description of Update Rollup 3 for Exchange Server 2010 Service Pack 1
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.