Backscatter - It's Okay to Be Impolite

In the world of unsolicited commercial email (a.k.a. spam), the perpetrators who send these messages often count on you being polite, or at least they count on your mail server being polite.  Back in 1982 when the whole idea of email was first taking form, the Internet Engineering Task Force set some standards.  One of the requirements for a properly-functioning mail server was this:  if you receive a message to an invalid address, you should politely return the message telling the sender that you could not deliver it.

In the world of unsolicited commercial email (a.k.a. spam), the perpetrators who send these messages often count on you being polite, or at least they count on your mail server being polite.  Back in 1982 when the whole idea of email was first taking form, the Internet Engineering Task Force set some standards.  One of the requirements for a properly-functioning mail server was this:  if you receive a message to an invalid address, you should politely return the message telling the sender that you could not deliver it.  This is called a non-delivery notice. 

Some years later spammers came along claimed their stake in the email world.  We in the information-technology industry have developed numerous measures to prevent them from delivering those annoying messages, and they’ve come up with just as numerous ways to thwart our spam filtering.  One of the more-effective methods to thwart spam-filtering measures is called backscatter.  It’s easy to fix, but recently we’ve come across some folks whose mail servers are not configured to prevent it.  Because of this, their legitimate emails were being marked as spam and not delivered. 

Here’s how it works.  A spammer forges an email from your email address to some invalid email address at a legitimate email domain.  We’ll call it bogus@legit.com.  When legit.com gets the spam message they politely return the message to you saying that it can’t be delivered.  What shows up in your inbox is their advertisement for interesting drugs, a diploma with no education, or millions of dollars from a Nigerian prince. 

How does one prevent this?  The owners of the legit.com email domain must tell their email servers to be impolite—to not send non-delivery notices.  Then this type of spam, known as backscatter, cannot be sent through their domain.  If they do not turn off non-delivery notices, spam-filtering services will prevent both spam and legitimate email from being delivered through their servers. 

How do I know if my email servers are sending backscatter?  Your email service provider should be able to tell you this.  If you know the IP address of your email-routing server, you can enter it at the link below, and it will tell you. 

http://www.backscatterer.org/?target=test

I would be remiss if I didn’t make a shameless plug for Innovative Networks’ INmon service.  This service monitors many important aspects of your technology infrastructure including an hourly verification that your email domains have not been blacklisted by spam-filtering services.  You can find out more information about INmon and our other proactive support services at the link below. 

Proactive Support