hi all,I have two backend cluster servers and two front end servers. My exchange server is running fine for 2 months long. Now my clients are encountering this problem very intermittently, When they send email to some recipients ,they get this NDR. But when they try to resend, the email is sent out without error.Please advise if u all happen to encounter this problem before.Your message did not reach some or all of the intended recipients. Subject: FW: monthly yield report Sent: 11/04/2007 9:46 AM The following recipient(s) could not be reached: 'username ' on 11/04/2007 9:46 AM The message could not be delivered because the recipient's destination email system is unknown or invalid. Please check the address and try again, or contact your system administrator to verify connectivity to the email system of the recipient. <myexchange servername #5.1.2>

check the dns settings on the smtp virtual server. sounds like it couldnt lookup the domain, then it could