The Setup:

Exchange 2007, Active Directory Empty Forest root with two Children domains DomainA and DomainB, Active Directory Sites and Services had both children domains in the same Site.

The problem:

Since the two domains were in the same AD site I deployed a SCC Mailbox Cluster in DomainA with two redundant Client Access Servers.  In DomainB I deployed a Single Mailbox Server.  Keep in mind, while testing this in the Lab everything worked without a problem, Mailbox Access and OWA.  OWA was really the big thing here since users in DomainB only access their mailbox via OWA.  When deploying this solution in production I received the error “Microsoft.Exchange.Data.Storage.ConnectionFailedTransientException” in the IE Window.  When accessing the mailbox on the mailbox server in DomainB using Outlook there were no problems!  Again, accessing via OWA the error message Microsoft.Exchange.Data.Storage.ConnectionFailedTransientException kept coming up.  This error message basically meant that OWA could not establish a connection to the backend mailbox server in DomainB.  This made absolutely no sense what so ever considering this deployment worked in my lab! 

So, after running some of the tests in Exchange 2007 and not being able to resolve the issue I contacted Microsoft Support.  Long story short, it turns out that the server administrator who build the mailbox server built it in DomainA.  Once he had the server built he then joined the mailbox server to DomainB where it became the mailbox server for DomainB.  As I’m sure we all know when a server is joined to a domain there is an object created in that domain that relates to the server.  What was occurring is that when I went to OWA and tried to access a mailbox in DomainB the CAS servers in DomainA were locating the mailbox server in DomainA.  The reason?  Well, since the Server Administrator created the mailbox server for DomainB in DomainA and then joined it to DomainB there was an active directory object for the mailbox server which never got deleted.  The CASs were trying to query a machine that no longer existed in their Active Directory Domain.

The Fix:

After spending three days on the phone with Microsoft Support trouble shooting the issue the resolution was simple.  Yup, you guessed it, delete the old computer object in DomainA. 

Once the computer object was removed from DomainA OWA worked again for users in DomainB.  Luckily I was still in test mode at that time and no users were impacted.  The unfortunate thing is I didn’t realize the server was originally build in DomainA.  I’m wondering how many people out there have made this mistake…..