In 2019, We Sent 83B Emails. Here’s What the Top Subject Lines Had In Common

As the world’s largest sender of personalized email, Sailthru sends millions of messages every minute. Throughout 2019, that translated to roughly 83 billion emails, a 7% increase over the previous year. Of course, it’s not just about sending email. It’s about sending good email, which won’t be opened without a strong subject line. Here are six observations about the top subject lines, based on the 500 messages we sent with the highest open rates.

Top Subject Lines Takeaway 1: Less Is More

Shorter email subject lines catch consumers’ attention more effectively. This is especially true as people increasingly read email on smartphones with more limited screen space. Among the most-opened emails, the average word count of the subject line was 8.7.

Top Subject Lines Takeaway 2: Up Your Trigger Game

During Thanksgiving and Black Friday last year, our clients saw a 20% increase in open rates when their email subject lines included a customer’s name, products they were specifically interested in, or products they were predicted to purchase.

This data set was much larger, but the fact remains: personalization impacts your open rate. We saw plenty of {firstname}, but many of the top subject lines incorporated personalization in other ways, namely triggered messages. Examples include:

  • Good News: Your Preorder Has Been Added
  • The style you’ve been eyeing is now in stock
  • Reminder: You still have $40 off!
  • Thank you for visiting!
  • Don’t forget your FREE birthday gift! Re: Order {ORDER_NO}

Top Subject Lines Takeaway 3: Make It About the Customer

Did you notice anything about the previous examples? Most of them contained the word “you” or “your,” two of the most common words we saw. Of the 500 top performing subject lines, 15% included “your,” while 12% included “you.” No matter your goal for an email campaign, remember that to achieve relevance, your message should ultimately be about the customer.

Top Subject Lines Takeaway 4: Create a Sense of Urgency

Two other words we kept seeing were “alert” and “breaking,” which appeared in a combined 20% of the top 500 subject lines. While breaking news is very media-specific, that doesn’t mean retailers can’t drive urgency. New arrivals, and back-in-stock and price drop notifications offer ample opportunity, especially when combined with key language choices. Here are three popular examples of the latter:

  • An exclamation point to convey excitement: Yay! Your coat just went on sale!
  • A single word capitalized for EMPHASIS: What’s New, HOT & Available? Check out the Latest!
  • Strong verbs to drive strong feelings: 1 Summer Dress You Need

Top Subject Lines Takeaway 5: Be Purposeful With Emoji

Emojis drive email opens and we expected to see many repeat offenders. Maybe the smiley face with heart eyes or the fire. However, unlike words, there weren’t any emojis that were particularly common. None of the brands behind the top subject lines included emojis just to include them. Every one fit in with the theme of the message:

  • A free mist just for your birthday! 🎁
  • Introducing the new April collection 👏
  • ✨ Ready, set, GLOW ✨

Top Subject Lines Takeaway 6: Be Open-Ended

Earlier this year, our friends at Emma researched the psychology of email marketing. Based on the Zeigarnik Effect, which refers to the brain’s tendency to remember incomplete tasks more clearly, Emma applied to this to the inbox by referencing our natural inclination to finish…

…reading sentences. See? We noticed the Zeigarnik Effect at play, between ellipses we automatically complete and questions we automatically answer. Of the 500 most-opened emails, 10% had either ellipses or a question mark in their subject lines.