GFI Software, developer of network security, content security and messaging software, has launched <A HREF="http://www.gfi.com/news/en/ndrspam.htm">a white paper to explain what NDR spam is all about</A> and why spammers have resorted to this effective method to distribute unsolicited mail.

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.