Good Day,In my exchange org each users has two different email addresses one forxyz domain (primary) and one for123 domain. When a user sends an email using the primary domain address to a not vaild address they receive an NDR. When they send a email using there other email address not primary to a not valid address they do not receive a NDR. The NDR's are getting stopped by our Hub servers and are queuing up on our DMZ SMTP relay server. The error that they are getting is connection refused. Now why would the Hub server except an NDR when it is sent using the primary domain email address and not except one when the email is sent using the secondary address?

What type of system do you have running as your SMTP relay? Does it do an LDAP query to your Active Directory to resolve inbound SMTP addresses? Also, out of curiousity, how are the users sending e-mail as their secondary address?Jim McBee - Blog - http://mostlyexchange.blogspot.com

Hi, Please check whether I understand the problem correctly: 1. When user send message to an invalid recipient by using primary email address. He is able to receive a NDR message 2. If the user send message to an invalid recipient by using secondary email address. The inbound NDR message is stuck on DMZ SMTP relay server and cannot be delivered to Hub Server. If I am off base, please let me know. Regarding the issue, I suggest you enable SMTP log on Receive Connector on the Hub Server and the DMZ SMTP relay server to check whether any error is encountered when the DMZ SMTP relay server attempts to send NDR message to Hub. In addition, I am also curious how the users send email by using secondary address. Mike