Posted 08 July 2009 - 08:50 PM
You can have a copy of all NDR's sent to your address which will give you the reason for Non-delivery.
Open System Manager. Click the plus next to Administrative Groups, the plus next to your group, the plus next to servers, then the plus next to your server name.
You should see "Queues, First Storage Group, and Protocols". Click the plus next to protocols then the plus next to SMTP. Right click on Default SMTP Virtual Server and click on properties. Click the messages tab. You will see "Send copy of Non-Delivery Report to:". Put your e-mail address in that box.
If and or when an NDR is generated, you will get a copy of it. It will then give you the reason for the NDR.
Hope this helps,
"Admire those who attempt great things, even though they fail."