February 2008

New study confirms that shorter subject lines
perform better

DALLAS– E-mail marketers’ first opportunity to capture a consumer’s attention is a subject line. Epsilon recently conducted research of subject line effectiveness in over one billion e-mails. Results indicate that while shorter subject lines do generally perform better than longer ones, the relationship between subject line length and response is weaker than previously thought.

Epsilon analyzed the impact of the more than one billion e-mails over nearly 20,000 separate campaigns sent out by a selection of US-based clients in the retail and consumer services industries. The research showed that, overall, shorter subject lines correlate with higher open rates and click rates for both industries.

The company’s experts evaluated the correlation between the length of a subject line of each campaign and the unique open and total click rates.  In addition to subject line length, the study suggests that subject line word order, word choice, and brand and audience awareness are also critical success factors. Additionally, it is crucial that marketers perform subject line testing to increase open and click rates.

According to Thane Stallings, Senior Analytic consultant, Epsilon Strategic Services, “Companies are spending little time thinking about and testing subject lines, compared to the resources and time devoted to creative development. The reality is that more people will see a subject line than its accompanying creative.”

Epsilon provides a full spectrum of services to help companies improve direct marketing and e-mail performance. For creating e-mail subject lines, the firm suggests the following rules of thumb:

1. Front load subject lines with the most important information.
2. Keep the subject line as short as possible to convey the message.
3. Use longer subject lines only when there is a compelling reason to do so.
4. When in doubt, test.
   The full report is available at www.epsilon.com/emailsubjectline.