Setting up a new Outlook profile throws the error with Exchange Server 2010: “The connection to Microsoft Exchange is unavailable. Outlook must be online or connected to complete this action.”

Problem

You attempt to set up a new mail profile with Outlook 2010 via autodiscover or manually:

… but receive the following message:

You must restart Outlook for these changes to take effect.

… followed by:

The connection to Microsoft Exchange is unavailable. Outlook must be online or connected to complete this action.

Clicking on the OK button brings up the Microsoft Exchange window with the Microsoft Exchange server field is filled in with the appropriate Exchange CAS server and the Mailbox field is filled in with: =SMTP:<email address>:

Clicking cancel reveals a red X beside the Log on to server step:

Solution

One of the reasons why this would happen is if the Microsoft Exchange Address Book service is stopped on the CAS server:

The issue I had while troubleshooting this was that the environment had 2 CAS servers load balanced via NLB where 1 of the CAS server had the service started while the other one didn’t thus causing some users to experience this while others did not so make sure that you check all of the CAS servers if there is more than 1 in the environment:

Once this service is started, Outlook should now successfully configure the profile: