Here’s how to read NDR’s. The server and reason for non-delivery is always in the bottom of the Non Delivery Report. Here is a sample:
From: Mail Delivery System [mailto:MAILER-DAEMON@smtp.abc.com] Sent: Wednesday, December 09, 2009 9:11 AM
Subject: Undelivered Mail Returned to Sender
-Here at first you can find the server who delivers the NDR to the Sender:
(in this sample smtp.abc.com) NOTE: This is only the deliver of the NDR, it has nothing to do with the reason why email relaying is terminated. The actual reason is always in the bottom of NDR.
This is the mail system at host smtp.abc.com.
I’m sorry to have to inform you that your message could not be delivered to one or more recipients. It’s attached below.
For further assistance, please send mail to postmaster.
If you do so, please include this problem report. You can delete your own text from the attached returned message.
The mail system
<firstname.lastname@example.org>: Recipient address rejected: undeliverable
address: host mx1.clientmail.com[188.8.131.52] said: 554 5.7.1
<email@example.com>: Relay access denied (in reply to RCPT TO command) (in reply to RCPT TO command)
-Message could not be delivered: server mx1.clientmail.com says: Relay access denied. It has terminated the transaction. All errors starting with ”5” are permanent errors, when starting with ”4” errors are temporary.
NOTE: Contact to the host of the server who gives the NDR.