When you start Microsoft Office Outlook 2007 to configure a Microsoft Exchange Server 2003 mailbox for use with Outlook 2007, you experience the following symptoms:
You receive one of the following error messages:
Error message 1
The connection to Microsoft Exchange is unavailable. Outlook must be online or connected to complete this action.
Error message 2
The action cannot be completed. The connection to Microsoft Exchange is unavailable. Outlook must be online or connected to complete this action.
Error message 3
The action cannot be completed. The connection to Microsoft Exchange is unavailable. Your network adapter does not have a default gateway.
If you click OK, the Microsoft Exchange dialog box appears. In this dialog box, the LDAP path (DN) of the Exchange 2003 mailbox server appears in the Microsoft Exchange server box. For example, /o=First Organization/ou=First Administrative Group/cn=Configuration/cn=Servers/cn=Exchange1.
If you click OK, the Outlook 2007 Startup Wizard starts or the Add New E-mail Account dialog box appears. When you follow the steps in this Wizard or when you click Next in the New E-mail Account dialog box, your e-mail account is configured successfully.
You experience this problem if the following conditions are true:
You have a Microsoft Exchange Server 2007 server that is running the Client Access Server (CAS) role in the Exchange 2003 organization.
Either of the following registry values are set on the computer on which Outlook 2007 is installed:
Value name: ZeroConfigExchange Value type: REG_DWORD Value data: 1
Your mailbox is located on a mailbox server that is running Exchange Server 2003.
You do not have an Outlook profile configured before you start Outlook 2007.
Note If you do not find the ZeroConfigExchange registry value in either of the registry locations that are mentioned earlier, you are not experiencing the problem that is described in this article. The problem with the ZeroConfigExchange registry value is just one confirmed reason that you can receive the error messages that are mentioned in the "Symptoms" section. For more information, including additional solutions, search the Microsoft Knowledge base (http://support.microsoft.com/search/default.aspx) for "connection to Microsoft Exchange is unavailable."
To work around this problem, use one of the following methods.
Method 1: Remove the ZeroConfigExchange registry data
Remove the Group Policy or the system policy that sets the following registry entry: