Outlook Web App isn't available for this mailbox. The Client Access server %1, running Exchange version %2, tried to find ...

Outlook Web App isn't available for this mailbox. The Client Access server %1, running Exchange version %2, tried to find a Client Access server to proxy Outlook Web App traffic for mailbox %3. It couldn't find the Client Access server in the target Active Directory site.

Additional information: %4. If the problem continues, contact your email admin.