E-mail open rate

The email open rate is a measure primarily used by marketers as an indication of how many people "view" or "open" the commercial electronic mail they send out. One of the earliest metrics applied in email marketing, its continued use is controversial due to conflicting views on its usefulness.

Open rates are typically measured using an HTML IMG tag embedded in outgoing emails, calling for a small, transparent tracking image. When the client or browser used to display the email requests that image, then an "open" is recorded for that email by the image's host server.

The open rate for an email sent to multiple recipients is then most often calculated as the total number of "opened" emails, expressed as a percentage of the total number of emails sent or -- more usually -- delivered. The number delivered is itself measured as the number of emails sent out minus the number of bounces generated by those emails.

This method leads to problems with interpretation, since the request for the tracking image gives no indication of whether the email's recipient actually viewed or read the email or its contents.

In addition, many webmail services and email clients block images by default, or the recipient may elect to receive text-only versions of an email. In both cases, no image call can ever be made, further reducing the accuracy of the open rate measure.

As a result, open rates are broadly rejected as an absolute measure of a commercial email's performance. However, many marketers use open rates as a relative measure, for example to compare the performances of emails sent to similar recipient groups, but at different times or with different subject headers.

See also

* Web bug
* E-mail tracking

References

Brownlow, Mark. [http://www.email-marketing-reports.com/email-open-rates/ "Email Open Rates Guide"] , Email Marketing Reports, August, 2006