Emails with subject lines of 6-10 words have the highest open rates, yet most emails sent by marketers have subject lines of 11-15 words, according to a recent report from Retention Science.

For the emails analyzed, those with 6-10 word subject lines had a 21% open rate. Those with subject lines containing five or fewer words ranked second with a 16% open rate, and those with 11-15 words had a 14% open rate.

Despite the effectiveness of shorter subject lines, most emails examined (52%) had subject lines of 11-15 words.

Below, additional key findings from the report, which was based on data from more than 260 million delivered emails.


Emails with the recipient's first name in the subject line had a higher open rate (18.3% compared with 15.7%).

Movie Names and Song Lyrics

  • A separate Retention Science study analyzed 3.7 million emails and 22 campaigns where movie names and song lyrics were referenced in the subject line, and discovered they perform considerably better than traditional subject lines.
  • Those emails with subject lines referencing movies or songs were opened 26% of the time, whereas emails with more traditional subject lines were opened 16% of the time.

About the research: The report's findings on subject line length and personalization were based on data from more than 260 million delivered emails and 540 campaigns. The findings on lyrics in email subject lines were based on an analysis of 3.7 million emails from 22 campaigns.

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The Most Effective Email Subject Line Length

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image of Ayaz Nanji

Ayaz Nanji is a writer, editor, and a content strategist. He is a co-founder of ICW Media and a research writer for MarketingProfs. He has worked for Google/YouTube, the Travel Channel, and the New York Times.

LinkedIn: Ayaz Nanji

Twitter: @ayaznanji