Exchange Server

New GFI Software White Paper Explains NDR Spam

I was recently informed by GFI Software that they have a new white paper that explains what NDR spam is and how administrators can take effective measures to reduce the impact on their email servers. As an email marketing manager, I found this white paper very helpful in understanding what NDR or non-delivery report spam is, and how spammers use it.

I have included a few excerpts from the press release below. To read the full press release on their website, click here. You can also download a copy of the white paper by clicking here.


NDR spam: When non-delivery reports become a nuisance

Research shows that up to 90% of emails received by companies are spam, and spammers have adopted a variety of methods to bypass spam filters used in anti-spam software. In the beginning, spam was mainly text based but over the past few years, spammers have resorted to using embedded images and attaching common file types such as mp3s and Excel documents in emails to gain access to mailboxes. Another option is NDR or non-delivery report spam.

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NDRs are a common part of email exchanges. Users receive NDRs, for example, when an email does not arrive at a recipient’s address and notification is sent to the sender. However, spammers can cause a considerable increase in NDR activity because they send junk mail to thousands of email addresses. Some are genuine but others are not and these are used to generate NDR messages by manipulating the ‘From’ address to use a real domain sender. This results in email users receiving NDRs from people they had never sent an email to in the first place.

Unless action is taken, email servers could be inundated with useless emails thereby hogging system resources and affecting performance. The best way to stop NDR spam is to deploy anti-spam software that can identify spam in NDRs and delete them from the server.

A variety of technologies are used and anti-spam software like GFI MailEssentials, the number 1 anti-spam filter on the market, uses Bayesian Filter, DNS Blacklists, Spam URI RealTime Blocklists and Keyword Checking to keep NDR spam at bay. GFI MailEssentials also uses a Directory Harvesting feature on the email gateway to drop email messages and NDRs sent to non-existent users.

This white paper explains what NDR spam is and how administrators can take effective measures to reduce the impact on their email servers.

For information on GFI’s anti-spam and anti-phishing solution, GFI MailEssentials, visit

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