Server Fault is a question and answer site for system and network administrators. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I'm a little confused on what exactly the "generating server" does in an NDR.

For example, I got the following NDR back when sending to a specific domain:

Diagnostic information for administrators:
Generating server:
#< #5.1.1> #SMTP#

Is the "generating server" the MTA that was the last hop to successfully accept the message and tried to deliver the message at the time of the error? Or is the "generating server" the server that gave back the 5.1.1 error (and did NOT accept the message)?

I also noticed the following:

Reporting-MTA: dns; 
Final-recipient: RFC822;
Action: failed Status: 5.1.1 
X-Supplementary-Info: < #5.1.1> 
share|improve this question
up vote 1 down vote accepted

The generating server is the server that gave back the 5.1.1

5.1.1 > Is in the bad-address failure category, meaning the server received the message, did an internal lookup and couldnt find a mailbox to deliver to and generated an NDR.

A detailed explanation is given here:

share|improve this answer

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.