Article ID: 2506820 - View products that this article applies to.
Consider the following scenario:
When Exchange 2010 in the remote organization detects an autodiscover query being performed for a legacy Exchange 2003 mailbox, Exchange 2010 will fail the lookup because Exchange 2003 does not support Autodiscover.
To resolve this issue, install the following update rollup:
(https://support.microsoft.com/kb/2579150/ )Description of Update Rollup 4 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.
A separate issue with Exchange 2003 Cross-Org lookups has been identified due to MergedOnly Free/Busy information being returned. For more information , click the following article number to view the article in the Microsoft Knowledge Base:
(http://support.microsoft.com/kb/2567863)Free/Busy information may not be returned when a Cross-Org query is performed from a legacy Exchange user
Article ID: 2506820 - Last Review: July 28, 2011 - Revision: 9.0