I've been working on this problem for several days and have tried tons of solutions to no avail. If anyone can help me with this I would be greatly appreciative. CAS redirection for /owa on a parent domain to user mailboxes on the child domain lets me login and shows the inbox; then errors after I click on any other folder within the account. OWA is enabled on the parent and child domain and internal DNS works fine. All firewalls are off for testing. If I login to OWA directly on the child domain, the user works fine. Additionally, if I go to the child domain and open the client access server, I get the following error: http://dl.dropbox.com/u/392447/child%20domain%20problem.PNG Replication is working fine. I have run /PrepareAD /PrepareAllDomains and /PrepareSchema successfully from the parent domain. Additionally, the child domain however will not upgrade to SP1 and gives the following error: Setup encountered a problem while validating the state of Active Directory: Exchange organization-level objects have not been created, and setup cannot cre ate them because the local computer is not in the same domain and site as the sc hema master. Run setup with the /prepareAD parameter on a computer in the domai n REMOVED and site Default-First-Site-Name, and wait for replication to complet e. Could this even be as small as an SSL problem? I installed the CA for each server in the rusted Root CA folder for each server so their certs should check out. I think all this points to something that someone can identify, but I just can't put it together. Any help is greatly greatly appreciated. This is causing one big roadblock for me! Here's the ASP error from OWA when connecting to a child domain mailbox from the parent OWA: Outlook Web Access could not connect to your Microsoft Exchange mailbox. If the problem continues, contact technical support for your organization. Click here to continue working. Request Url: https://removed:443/owa/forms/basic/BasicMessageView.aspx?ae=Folder&id=LgAAAADr3Zu75gi9Tbp6TclNo5HSAQAeyQJY5DnnTIARg1o8HiZ0AAACWO2vAAAB&pg=1&slUsng=0 User host address: 216.75.233.50 User: SJC TEST EX Address: /o=removed/ou=Exchange Administrative Group (FYDIBOHF23SPDLT)/cn=Recipients/cn=sjc.test SMTP Address: SJC.TEST@removed.com OWA version: 8.0.685.24 Exception Exception type: Microsoft.Exchange.Data.Storage.ConnectionFailedTransientException Exception message: Cannot open mailbox /o=removed/ou=Exchange Administrative Group (FYDIBOHF23SPDLT)/cn=Recipients/cn=sjc.test. If you have ideas please share!