Hi We have just moved to Windows 2003 and Exchange 2003. I have problem whereby sometimes from random users email sent to local recipients bounces back with a message: Joe Bloggs on 1/19/2005 6:09 PM The message could not be delivered because the recipient's destination email system is known or invalid. Please check the address and try again, or contact your system administrator to verify connectivity to the email System of the recipient. <servername.company.co.zw #5.1.2> Users will immediately retry and the message will be delivered. This happens randomly and the users are getting irrate. I have 3 domain controllers ofwhich the Exchange server is one of them and is the Global Catalog Server. All other email flow seems to be fine. HELP. Naboth