You have deployed a computer that is running Microsoft Exchange Server 2007 in a disjoint namespace. However, when you run the Test-ActiveSyncConnectivity command in Exchange Management Shell, the command returns the following error message:
Could not find or log on with user <DNS_DOMAIN_FQDN>\CAS_<GUID>. If this task is being run without credentials, please log in as a Domain Administrator, run the Scripts\new-TestCasConnectivityUser.ps1 to verify that the user exists on the mailbox server <server name>
You receive this error message even though Exchange ActiveSync works. Additionally, all the Test-* commands that are related to the Client Access server fail and generate a similar error message. Also, when you use the Exchange Management Pack in Microsoft Operations Manager (MOM), it will fail for the same reason.
Note If you use the get-mailbox command to check the CAS_<GUID> mailbox, you may see that the mailbox exists on the Exchange server.
This issue occurs when a test user is automatically created after you run the Test-ActiveSyncConnectivity command on the Client Access server. When the user is created, the UserPrincipalName property will be set with the domain name of the Mailbox server. The current behavior is that the Exchange server assumes that Mailbox server's domain name is always an Active Directory directory service domain name and uses the UserPrincipalName property as part of a "domain\user" format. However, the Active Directory domain name does not apply in a disjoint namespace scenario.
To resolve this problem, install Update Rollup 7 for Exchange 2007 Service Pack 1. For more information about Update Rollup 7 for Exchange Server 2007 Service Pack 1, see the following Exchange Help topic: