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Clickbait Email Subject Lines Don’t Work, Return Path Study Finds

Consumer Behavior Unaffected by Email Subject Line Length

NEW YORK, 28 April, 2015 – Data solutions provider Return Path today announced findings from a new research study on email marketing subject lines, contradicting several widely held beliefs about consumer preferences and behavior.

Return Path’s findings showed that “clickbait” subject lines, like “You won’t believe this shocking secret…” while highly successful at capturing web traffic, were among the least effective of the ten subject line types examined. The use of “Secret of” accompanied an 8.69% decrease in read rates compared to messages containing similar content sent under different subject lines. The word “shocking” accompanied a 1.22% decrease in read rates.

The analysis of more than 9 million messages sent by prominent global brands to more than 2 million consumers revealed that benefit-based subject lines featuring superlatives like “fastest” (which coincided with 5.30% higher read rates than comparable messages sent under different subject lines) were better at getting consumers’ attention. Read rates for urgency-based subject lines including “limited time,” “last chance,” and “expiring” were also elevated.

Two classes of value-based subject lines yielded unexpectedly low performance: those promoting prices and discounts. Subject lines containing keywords that identified discounts, including “discount,” “save,” “sales,” and “clearance” coincided with lower read rates. Those including pricing references such as “free,” dollar signs, and percentages also accompanied lower read rates than comparable messages with different subject lines.

Don’t Bother Counting Characters

On the other hand, subject line length–a frequently debated factor in the effort to get consumers to read email messages–made no real difference at all. Although subject lines that ran longer than 100 characters correlated to the lowest read rates (8.8%), those between 91 and 100 characters were among the best-performing in the survey (15.1%). The most common range – 40-to-49 characters – used in 25% of all messages, coincided with some of the lowest average read rates in the sample (11.6%). Read rates happened to be substantially better for both slightly longer and slightly shorter subject lines, but any appearance of correlation is clearly random. Outside of obviously overlong examples, this research suggests that subject line length debate should be put to rest.

“Subject line optimization presents one of the clearest opportunities to apply advanced analytics toward understanding and significantly increasing marketing performance,” said Return Path President George Bilbrey. “By analyzing extremely large data sets collected across the entire email ecosystem, based on how real subscribers engage with messages sent from thousands of trusted brands, marketers can quickly, efficiently, and confidently test subject lines to ensure that their messages are read by as many people as possible. As this study demonstrates, the results are often surprising, frequently questioning or even invalidating long-held best practices.”


For this study, Return Path analyzed over 9 million subject lines received by more than 2 million subscribers from January 1st through February 28th, 2015 using its Subject Line Optimizer solution.

About Return Path

Return Path analyzes the world’s largest collection of email data to show marketers how to stay connected to their audiences, strengthen their customer engagement, and protect their brands from fraud. Our solutions help mailbox providers around the world deliver great user experiences and build trust in email by ensuring that wanted messages reach the inbox while spam and abuse don’t. Find out more about Return Path email optimization and email fraud protection solutions at