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.
The set of folders could not be opened.
The information store could not be opened.
Unable to display the folder. The information store could not be opened.Additionally, you receive the following error message when you send an e-mail message by using Outlook 2003:
Task 'Microsoft Exchange Server - Sending' reported error (0x800C8100): 'Unknown Error 0x800c8100'
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.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
Article ID: 978777 - Last Review: Feb 16, 2017 - Revision: 3