Email newsletters with short subject lines (4-15 characters) had the highest average open rate (15.8%) last year, according to MailerMailer's annual Email Marketing Metrics Report.

Longer subject lines resulted in lower open rates, though the effect on open rates diminished as the lengths increased.

Click rates also peaked when subject lines were kept short. Subject lines of 4-15 characters had the highest click rate (2.6%). Very long subject lines—over 51 characters—had the lowest click rate (1.6%).

Below, additional key findings and benchmarks from the report, which was based on an analysis of 1.4 billion opt-in email newsletters sent during 2012.

Open Rates

  • Email newsletter campaigns sent in the first half of 2012 had an average open rate of 9.7%, and those sent in the second half of the year had an average open rate of 10.0%.
  • Open rate peaked in the first hour after delivery, declined rapidly within the next 19 hours, and gradually diminished thereafter.
  • About half (51.7%) of all opens occurred within the first six hours after delivery. At 18 hours after delivery, three-quarters of total opens had occurred.


  • In the first half of 2012, open rate peaked on Tuesdays and Wednesdays at 10.7%. In the second half of the year, the highest open rate (10.6%) was on Tuesdays.
  • Sundays had the highest click rates—2.2% and 2.6% during 1H12 and 2H12, respectively. Tuesdays had the next best click rates for both halves of the year.
  • Messages scheduled for delivery between early evening and early morning led to better open rates.
  • Both 1H12 and 2H12 experienced their lowest open rates, 5.5% and 7.9%, for messages scheduled for 12 PM.
  • Open rates climbed rapidly after 4 AM, and peaked at 10 AM, after which they declined steadily throughout the rest of the day. 
  • In general, emails were more likely to be opened during normal business hours, specifically between 8 AM to 5 PM.


Open Rates

  • Personalizing only the email message content resulted in a higher average open rate of 13.2%.
  • Personalizing just the subject line increased the average open rate to 12.9%.
  • However, when both the subject line and message content were personalized, open rate dropped to 5.3%—lower than that of messages with no personalization at all (9.8%).

Click Rates

  • In contrast to the open rate data, personalization of both the subject line and message content resulted in the highest click rate (2.8%).
  • Personalization of only the message and only the subject line resulted in click rates of 2.4% and 2.1%, respectively.
  • Messages with no personalization had the lowest click rate (2.0%).

About the research: The report was based on data from over 1.4 billion opt-in email newsletters, from over 70,000 newsletter campaigns, sent between January 1, 2012 and December 31, 2012.

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Email Newsletter Benchmarks: Open Rates, CTRs, Subject Lines

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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