Exchange Online breaks AutoDiscover for additional Exchange mailboxes

I was getting an error message on a single physical Windows 7 machine, which was a brand new install of Windows 7 with Office 2010 SP1. Outlook is connecting to Exchange 2010 SP2 which hosts all mailboxes for the company. I was getting this error on the first Outlook setup screen where I enter, name, email address and password: (An encrypted connection to your mail server is not available. Click next to attempt using an unencrypted connection) This error was happening the first time I configured Outlook 2010, right after installation. The Windows 7 machine is not on the domain. However, when I did exactly the same thing to test on a VMware virtual copy of Windows 7 which also wasn’t connected to the domain and running on top of the exact same physical machine using Office 2010 SP1 with the same user/mailbox etc, it worked perfectly.

There’s about 200 users in the company and no other users have a problem like this. Problem is happening only on this one machine which I formatted and rebuilt completely with a fresh copy of Windows 7 and Office 2010. One of the reasons why I rebuilt this machine was because I was getting this issue before with Outlook. When I hit CTRL and right clicked on the Outlook icon, then ran the Test E-mail AutoConfiguration, I was getting the error message (srv record lookup for http://autodiscover.<company>.com/au…todiscover.xml Failed (0x80072EE2)). When I tested using with the same mailbox account, it worked perfectly.

Outlook 2010 SP1 couldn’t add the users mailbox for the company by using AutoDiscover.

What was happening?

Outlook 2010 has the ability to add multiple Exchange accounts to the one Outlook profile. There was an already existing exchange account hosted with Exchange Online which was setup in Outlook 2010 by using the Microsoft Online Services Sign In client. This client automatically configures Outlook for Exchange Online use, as AutoDiscover doesn’t really exist for Exchange Online mailboxes due to a non-existent SSL certificate with the name autodiscover.<mydomain>.com. During configuration of Outlook, the Microsoft Online Services Sign In client configures other settings, one of which manages to break adding a second exchange account using AutoDiscover. The single key that was the culprit is HKEY_CURRENT_USER\Software\Microsoft\Office\14.0\Outlook\AutoDiscover\ExcludeHttpsAutodiscoverDomain This was set to a value of 1. I simply deleted this key after backing up the registry and all of a sudden Outlook allowed me to add a second Exchange account using AutoDiscover. There’s an article online which documents these changes by the Microsoft Online Services Sign In client and gives instructions to Revert Autodiscover Changes for Exchange Online

I don’t know what exactly the key ExcludeHttpsAutodiscoverDomain does, and if it is really required for Exchange Online? But it seems at this point in time, it was a hack and not a glorified fix that solved the problem. So if anyone knows a better solution to happily have an Exchange Online mailbox and a company Exchange mailbox in the same Outlook 2010 profile, please let me know.

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