The Client Access server doesn't have the InternalURL value set for the Microsoft-Server-ActiveSync virtual directory. This ...

The Client Access server doesn't have the InternalURL value set for the Microsoft-Server-ActiveSync virtual directory. This prevents Exchange ServiceDiscovery from finding the MobileSyncService information for user %1. At least one Client Access server in the user's mailbox Active Directory site must have the InternalURL value set. The format for the InternalURL value is https://hostname/Microsoft-Server-ActiveSync