Email subject line best practices

The saying, "You never get a second chance to make a first impression" has never been more true. In email marketing, the first contact you have with readers can make or break a new relationship. We know our prospects are judging how perceptive we are about them. So, how do we win them over with one short sentence?

According to research at Gartner , when a subject line is misaligned with the content of the email, 30.4% of respondents said they'd unsubscribe. In that same study, Gartner found that only 31% of brands used personalized subject lines in email campaigns. With all this potential for improvement, it’s important to look at the do's and don’ts of writing an email subject line in 2024. Follow along as we go over the fundamentals of what your subject line should possess and how to leverage email marketing software to measure performance.

What you’ll learn:

• Why are email subject lines so important?
• What type of email subject lines work best?
• What are some examples of great subject lines?
• What are some common mistakes to avoid when creating email subject lines?
• What are the best practices for creating email subject lines?
• How do you test your email subject lines?

Smart email subject lines are a glimpse into your content's value and can arouse your reader's curiosity. And that’s true even if your prospects don’t actually open an email. Consistently writing compelling subject lines works to build brand recognition and a sense of familiarity. Quality subject lines increase email deliverability rates, meaning emails won’t be marked as spam. Making sure your messages reach the intended audience contributes to a positive relationship, increasing the likelihood of future engagement.

You may have already played with a mix of different email subject line styles. There’s a ton to work with, and each has their own set of values and risks. Which sort of subject line works for you? Let’s get into it.

A curiosity-driven subject line piques recipients' interest. A subject line like, "Unlock the Secret to Effortless Productivity!" implies there's a hidden key to achieving an easy workflow. Your recipients open the email with the hope of discovering the secret. The potential downfall here is their disappointment. Managing expectations is crucial; otherwise, there's a risk of a negative impact on trust if your content doesn't match their initial curiosity. provide valuable insights or tips related to productivity to meet the expectations set by the subject line. The upside of curiosity is higher open rates and memorable branding. Everyone remembers content that is intriguing or establishes connection, and brand recall is important for the long haul. Avoid overusing curiosity-driven subject lines and prospects won’t feel desensitized with the frequency of your messaging.

A benefit-focused subject line emphasizes the value recipients gain from opening your email. For instance, "Boost Your Efficiency with Time-Saving Hacks!" directly communicates the advantage of reading the content. Recipients anticipate learning time-saving strategies – a tangible gain. The potential risk here is if the promise isn’t substantiated. Who wouldn't begin to distrust the sender if the subject line and content don’t match? The opposite is also true: When you’re honest, a prospect will feel impressed. Strike that balance and readers will be receptive to your messaging without feeling misled..

A question-based subject line prompts your readers to think. A subject line like, "Ever Wondered How to Master Time Management?" encourages you to open the email in search of an answer. The strength of this style is its ability to promote interaction. When you use these, make sure you effectively address the posed question. We’ve all clicked on something only to read content that feels super out of place. It’s a matter of authenticity: You want your recipients to perceive your email (and your brand!) as a valuable source of information rather than a mere attention-grabbing tactic.

An urgency-based subject line creates a sense of immediacy. For example, a subject line like, "Last Chance: Exclusive 24-Hour Sale Ends Soon!" motivates recipients to open the email to avoid missing out. The advantage of this style is its potential for driving immediate action and conversions. But maintaining credibility is key, as false urgency can lead to a loss of trust. No one likes when a marketer cries wolf! Balancing the urgency conveyed in the subject line with the actual time constraints in the email content and you will encourage engagement.

Effective subject lines depend on your specific audience, industry, and goal. You can explore your inbox for real-world examples that captured your attention and inspired you to click, sign up, make a purchase, join, etc.

For me, it’s often the emails from places I’ve visited in-person that catch my interest. I gave Levi’s, for example, my email so that I could enjoy 10% off my first in-person purchase. Now they’re sending me emails with catchy headlines like “Sale-abration,” with a coupon for 50% off bestsellers. Another Levi's email subject line used a clock emoji with the subject line, “Time for more ⏰ for you.” Now that it’s a new year, Levi’s is using the New Year, New You tagline to inspire the reader and shopper to make time for themselves. Who doesn't love encouragement to take care of themselves, especially after a busy holiday season shopping for others?

Harry & David is another example from my inbox. Having recently purchased holiday gift baskets for relatives in different states, Harry & David are now sending me messages that have the discount amount in the email subject line. When I click on the email that says, “Sharing is easier with 20%” or “Take 20% off great gifts for great days ahead,” or “Happiness starts here: 20% off for gifts to share,” I note a few things. The first is that they are consistent. When I read the email, I can see that sure enough, the 20% discount offer stands. Number two is this spirit of generosity. It felt good to share the baskets (indeed my family loved them - and it was so easy!) and their message stays on point every time. I know I can easily unsubscribe from their list, but I won’t, and that’s because the emails don’t come too frequently – maybe once a week. It's a reminder that I can use this service again, and get a discount when I do.

Some other examples that don’t involve that first in-person shopping experience might be email subject lines like:

"Flash Sale: 50% Off for the Next 24 Hours!"

This subject line creates a sense of urgency with the term "Flash Sale" and offers a significant discount, motivating recipients to open the email promptly to take advantage of the limited-time offer.

"Your Exclusive Invitation: VIP Access to New Collection."
By using terms like "Exclusive Invitation" and "VIP Access," recipients feel special and privileged, tapping into the psychological desire for exclusivity and driving higher open rates.

"Don't Miss Out: Limited Stock Left of Your Favorite Items."

The subject line combines urgency ("Limited Stock Left") with a personalized touch ("Your Favorite Items"), creating a compelling reason for recipients to open the email and secure items before they run out.

"Your Cart Misses You – Enjoy 10% Off to Complete Your Purchase."
This subject line uses a personalized touch by mentioning the recipient's abandoned cart, coupled with an enticing offer ("Enjoy 10% Off"), reengaging prospects and boosting conversion rates.

"Unlock a Surprise Gift Inside – Open to Reveal."

This subject line entices recipients with the promise of a surprise, prompting them to open the email to discover the hidden gift and enhancing overall engagement.

"Final Hours: Free Shipping on All Orders!"
"Final Hours" creates urgency and offers a tangible benefit ("Free Shipping"), incentivizing recipients to open the email quickly to take advantage of the time-limited offer.

You can be proactive in your campaign effectiveness by avoiding too much promotional language. Excessive exclamation points or writing in all capital letters may trigger spam filters and diminish your email deliverability. Repetitive sales phrases can make subject lines seem generic, while making exaggerated claims with superlatives ("The Best Weight Loss Program Ever!" or "The Ultimate Solution for Perfect Skin!") can erode trust.

Misleading language that creates false urgency or curiosity without justification may result in disappointment and a decline in trust. Remember, the body of the email should match the promise of the subject line. Most of us open emails on our phones, so neglecting mobile optimization can contribute to lower open rates. Using overly complex language for a simple product ("Revolutionizing Turf Wellness through Holistic Botanical Harmonization" - what a mouthful!) or neglecting A/B testing misses opportunities for refining subject line strategies based on audience preferences.

These days, personalization is the name of the game. A subject line like, "Dear [First Name], Discover Our Exclusive Offers!" is not it. All this tells your prospect is that your database or automation system has encountered an error, and sent the email with the "[First Name]," placeholder. This gives the appearance of a mass-produced message.

And while humor can be effective, using overly edgy or provocative language may be off-putting. Take this example, for lawn care: "Unleash Your Wild Side: Our Lawn Care is Hotter Than Your Neighbor's!" This subject line risks being perceived as unprofessional or insensitive. What’s funny to one isn’t funny to all.

Beware of the clever email subject line that lacks specificity and fails to convey any clear information about the email's contents. Something like "Cracking the Code: The Mystery Inside!" might pique curiosity, but your recipients may not be motivated to open the email as the subject line doesn’t really hint at the value they would gain.

There are a handful of tactics for crafting effective subject lines. Consider the following as you get started:

• Use dynamic personalization to insert the recipient's name into the subject line. For instance, a subject line like "Hey John, Unlock Your Exclusive Offer!" creates a sense of individualized communication. You can use data on the recipient's past interactions to craft subject lines that make them feel special. You can tack on to that personalization and create a sense of urgency with time-sensitive offers, like this:"Only for You: 24-Hour Flash Sale on Your Favorite Products!"
• The use of visual elements like countdowns or timers in subject lines intensifies the perception of limited time. "Hurry! Only 6 Hours Left to Claim Your Exclusive Deal!" And using scarcity language taps into the fear of missing out (FOMO). For instance, a subject line like "Limited Stock: Your Chance for a Special Edition" motivates recipients to open the email promptly.
• Keep your email subject lines concise. Aim for subject lines under 50 characters to ensure visibility on mobile devices and other modalities. By front-loading important information, you’ll capture attention quickly. For instance, "Save 20% Today on Your Favorite Items" conveys the offer at the beginning. Use email testing tools to preview subject line appearance across different devices to make sure they’re all visible. A subject line like "Unleash Savings! Limited Time Offer; Take Advantage Today!!!" might get truncated on certain platforms.
• Use emojis thoughtfully and pose questions in your subject line to pique curiosity. Emojis can add a playful element and be visually appealing if used sparingly. For example, "🌟 Your Exclusive Access to New Arrivals 🌟" not only conveys excitement but also breaks up text, improving readability. For a health and fitness brand, using emojis like 🏋️‍♂️ for strength or 🥗 for nutrition can enhance the subject line's relevance and resonate with the audience.
• Craft subject lines as open-ended questions to ignite curiosity. For instance, "Ever Wondered How to Achieve Amazing Skin?" prompts recipients to open the email to discover the answer. Tailoring questions to resonate with the recipient's interests, like this: "Ready for Your Next Adventure? Explore Our Exclusive Travel Deals!"
• Power words are terms that evoke strong reactions, such as "exclusive," "unleash," or "transform." Emotional triggers such as "excitement," "joy," or "surprise," affect recipients on a personal level. For example, a subject line like "Experience the Joy of Savings – Limited Time Offer Inside!" combines a power word ("joy") with an emotional trigger ("limited time offer"), creating a persuasive message that encourages recipients to open the email.
• Tailoring subject lines to specific audience segments is key, but you need to first understand their preferences, behaviors, and needs. A technology company might use language that appeals to advanced technologists, while simultaneously adopting a different tone (and content) for those interested in more user-friendly features. A personalized approach boosts open rates and creates stronger bonds between the audience and the brand.
• Storytelling is a mainstay for building emotional connections. Humans are naturally attracted to a sense of narrative intrigue. For example, a subject line like "Embark on a Culinary Adventure: Our Chef's Inspirational Journey" hints at a story. It’s an invitation to learn more about the chef's experiences and culinary creations.

• A/B testing is when you create distinct groups within your email list where each group receives a different subject line. Monitor the A/B testing results and other key metrics like open rates, click-through rates, conversion rates, and bounce rates to see where you can improve – and incorporate randomization and statistical significance in your results.
• Consider segmenting your audience for more targeted testing, and incorporate customer feedback when you go back to the drawing board. Data analysis is essential for refining subject line effectiveness, so make sure your team is up to speed in learning how to make the right changes. AI plays a role in this. When properly deployed, it can automate A/B testing processes, experimenting with subject line variations to decide on optimal combinations.
• AI-powered tools excel in processing vast datasets. This means they can provide nuanced insights into user behavior, preferences, and trends. And machine learning algorithms can identify patterns within metrics (open rates, click-through rates, and conversions).
• Personalization, urgency, and testing are among the top ways to create email subject lines that make a real difference. And in the wake of evolving data privacy regulations, email, driven by first-party data, still reigns supreme. You can apply the learnings your testing and analytic provide across all parts of your campaign, not just optimized subject lines. This is where having your team be trained up on the foundation of data and AI is important: Strengthen your understanding and you’ll see the benefits in the broader marketing landscape.