Office Outlook 2003 does not connect to two or more additional mailboxes in a mixed Exchange Server 2007 and Exchange Server 2010 environment

Consider the following scenario:

• In a mixed Microsoft Exchange Server 2007 and Microsoft Exchange Server 2010 environment, you configure your user profile in Microsoft Office Outlook 2003 to access your primary mailbox.
• Your primary mailbox is hosted on an Exchange Server 2007 Service Pack 2 (SP2) server.
• There are additional mailboxes that are hosted on an Exchange Server 2010 server.
• You try to access two or more additional mailboxes at the same time by using Office Outlook 2003.

In this scenario, you are able to access one additional mailbox or shared folder. When you try to access the second additional mailbox or shared folder, you receive one of the following error messages: Additionally, you receive the following error message when you send an e-mail message by using Outlook 2003:

The issue that is described in the "Symptoms" section occurs when your primary mailbox is hosted on an Exchange Server 2007 Service Pack 2 (SP2) server.

To resolve this problem, install the following update rollup:

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.