The Email Open Rate Metric

The open rate for emails is the most cited metric in email marketing. It is becoming, however, a hotly discussed metric. The discussion mainly falls on the definition of the open rate, as well as the ability to confirm the validity of the open rate however it is defined.

While definitions vary slightly, the definition most cited and accepted is the number of individuals who open an e-mail divided by the net number of emails delivered after all the bounces are subtracted.

This seems simple enough, except that we also need to define when an email is opened. An "open" is impossible to track in a text only email. An open is tracked in an html email when the receiving computer calls for a graphic that is within the e-mail. As Internet service providers, corporate IT departments, and email client applications increasingly block images by default, some mail is getting opened and is not being registered as an open.

Further, email client applications are changing rapidly. Many applications have a preview pane to view an email. This preview pane can collect the images, thus register that email as an open, even if the end user is simply scrolling through his list of emails. That is to say, the receiver may have looked at the email or he may have scrolled right over the email without a pause. Also, with more people carrying Blackberrys, iPhones, and other personal digital assistants, the accuracy of the open definition is even more in question.

The discussion then becomes, is this open rate metric a valid tool. I believe it is. While not 100 percent accurate, it does give valuable insight into the effect of the email campaign. In the text- only days it was extremely difficult to gauge email marketing effectiveness. Using this metric with other statistical analysis (web traffic statistics, landing page statistics, click through rates) will continue to give meaningful information to your email marketing team.