The Recipe to Subject Line Success

Allison Howen
by Allison Howen 05 Mar, 2014

The search for the perfect email subject line may finally be over, as a new study from Retention Science is shedding light on what attributes result in the highest open rates for marketers.

The study, which analyzed more than 260 million delivered emails and 540 campaigns, found subject lines with 6 to 10 words tend to perform the best, generating a 21 percent open rate. Subject lines containing five or fewer words came in second with a 16 percent open rate, while subject lines with 11 to 15 words returned the lowest open rate at 14 percent. Despite these stats, 52 percent of the studied emails had subject lines in the 11 to 15 word range.

"Subjects lines are arguably the most critical component of any email marketing campaign, as they're the first thing people see in their in-box and what they consider when making the decision to open or trash an email," said Jerry Jao, CEO of Retention Science. "Our findings show brevity is the key to enticing customers to engage with offers, and ultimately, to click through and convert."

The Retention Science study also found that 35 percent of emails are opened on mobile devices, which is actually a smaller number than a recent Movable Ink study found. That said, mobile could be a reason why subject lines with fewer words perform better, as most smartphones only display five or six words. It is also important to note that personalization can help re-engage and retain customers. For example, the study found campaigns that included the recipient's first name resulted in a 2.6 percent increase in open rates compared to those without a name.

Some of the study's most surprising data actually unveiled a new trend in email subject lines, finding that the use of movie titles and song lyrics is on the rise. In fact, a separate Retention Science study that focused on this trend found that subject lines referencing movies or songs were opened 26 percent of the time, while more traditional subject lines were opened just 16 percent of the time.

"Email marketing remains one of the most effective and lucrative digital marketing strategies, but there's always room to improve and capitalize on emerging trends," said Jao. "Movie and music references can be targeted to certain customer segments or encapsulate a promotional theme, making them a creative way to hypertarget and capture attention." 

The study also shed light on underperforming subject lines, revealing that the majority of flash sale campaigns resulted in disappointing open rates. The data shows that almost 80 percent of flash sale campaigns had subject lines with 20 or more words, and these campaigns consistently underperformed when compared to emails with shorter subject lines. It is important to note, however, that the frequency of which these emails are sent could also be a factor in poor performance, as flash sale brands tend to send emails four to eight times a week. Comparatively, the average frequency for most campaigns is two to four times a week.