Document information

Document ID: 4543
Subject: What is an NDR
Creation date: 12/14/15 4:35 PM
Last modified on: 12/17/20 4:15 PM

What is an NDR?

NDR stands for non-delivery report. When an email message is composed and sent to an invalid email address the receiving, or in some cases the sending, email server attempts to send an NDR to the sender of the email message, to inform them that the email address used is invalid.

What are the pros and cons of sending NDR?

On one hand NDRs are useful in a sense that they notify the sending of any non-deliverable messages, on the other hand they can be misused by spammers. Consider the following example:

  • A spammer wants to send a junk message to user A
  • This spammer knows that A's email server is running a spam filtering system that will prevent the message from going to A's inbox
  • The spammer puts A's email address in the From/Sender field rather than TO/CC and puts an invalid address in the To field
  • The message is sent to the invalid email's server, which generates an NDR and tries to send it back to the sender.
  • However, the spammer had forged the sender's address to be A and therefore, he/she gets the email.
What options does Xeams provide to prevent spamming using NDR?

What options does Xeams provide to prevent NDR related spamming?

Xeams provide two different options that can reduce the misuse by spammers. To access these options in Xeams, login to the administration console, click SMTP configuration under Server Configuration and then select the Advance Configuration tab.
  1. Include original - When this is checked, the original message is also sent in the NDR. When it is NOT checked, the server will only send the email header. This option is not selected by default. 
  2. Generate for outbound emails - When checked, NDR will be generated only for outbound messages. We recommend using this option if you see a lot of messages being sent to invalid users.

User comments

Posted by Simon Bendall on 12/15/15 6:51 AM

It would be really helpful if the templates for the delivery notification and non-delivery reports could be modified.

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