You add a new domain to the accepted domain list in a Microsoft Exchange Server 2007 organization. When you send an e-mail message to this new accepted domain, you may receive the following NDR message:
550 5.7.1 Unable to relay for user@domain.com
The NDR message indicates that the new accepted domain does not work.
Additionally, the following event is logged in the Application event log:
Event Source: MSExchange ADAccess
Event ID: 2803
Description:
Process %1 (PID=%2). The Active Directory notification callback for %3 has timed out. Exchange Active Directory Provider will no longer deliver configuration change notifications to the component.