10 Tips for Better Email Subject Lines

Are the subject lines of your emails important?

Absolutely—maybe more than you think. It's not just about higher open rates. Every time a subscriber chooses not to open one of your emails, you miss an opportunity to engage with them and strengthen that relationship. Additionally, your list members are less likely to take the desired action, such as making a purchase, if they don't open your emails. Over time, you also train your customers to ignore your messages, which can lead to a lot of problems.

When so much depends on a simple subject line, you want to do everything you can to make your subject lines as strong as possible. Take a few minutes before you send your next email and use one or more tips from this list.

1. Highlight the discount

Are you sending an email with a discount code in it? Don’t worry about being clever or reserved. Be as clear as possible. Is "Get 10% off your next purchase" a boring subject line? Yes. But that’s precisely the point.

As host Kurt Elster said in a conversation about subject lines for discount emails on The Unofficial Shopify Podcast: “The smarter I get with the subject lines, the worse they perform. You really want to be very direct.”

2. Do a ‘specificity sweep’

Joanna Wiebe from Copy Hackers has a handy technique you can use for email subject lines: the specificity sweep. In this video she walks you through the process of applying it to an entire email. But it’s also a quick and effective (though not easy) technique you can apply to subject lines.

In short, look at your text and ask yourself if it's too broad and therefore annoying: "Check out our new spring items." It won't upset anyone, but are people really inspired to click? Specificity can feel a bit risky. But if you want people to open your emails, take a look at your subject lines and look for ways to be more specific.

3. Get inspired by 164 examples

We're fans of OptinMonster—it’s one of the great third-party email acquisition tools you can integrate with your Klaviyo account. And if you’re looking for inspiration, you’ll love their list of 164 of the best email subject lines.

From FOMO to humor to straightforward subject lines, these examples—from retailers, SaaS companies, and famous people—will get your imagination going.

4. Follow a headline formula

If you’re more process-oriented, dive into subject lines and discover how to create a winning email subject line. Sumo's long list of headline formules gives you countless options to choose from, ready to personalize and make your own.

For instance, according to the list, you can use the formula “[Insert Celebrity] School Of [Topic]” to write subject lines like “Bruce Lee's School of Self Defense” or “Stop [Action]!” to write "Stop Reading the News!" It’s a great way to go beyond your usual subject lines and think differently.

5. End with a question mark

Should you always end a subject line with a question mark? Of course not. That would be excessive. But when the Fashion Ecommerce Benchmark Report was compiled (get a free copy!), it turned out to be a good rule of thumb sometimes.

Yotpo analyzed 3.5 million emails that retailers sent to ask customers for reviews. It turns out that the punctuation at the end of an email subject line makes a difference. Ending with an exclamation point? Expect a 27% decrease in review conversions. Ending with a question mark? You could see a 23% increase.

6. Write 25 subject lines

How many possible subject lines do you write before choosing the one you’ll use? One? Maybe two or three? Look at the famous Upworthy method of writing 25 headlines for every article ( Find out what it's like to actually do that) Create 25 possible subject lines for your next email campaign before picking a winner.

If that sounds excessive, try it anyway. As anyone who has tackled the popular creative writing exercise “40 Uses for a Rock” can tell you, your creativity really takes off. You might end up with surprisingly good ideas.

7. A/B test with a purpose

We can’t say enough good things about the values of A/B-testing various elements in your emails, including subject lines. If you want to A/B test your two favorite headlines, that's a solid use case. But it’s even better to conduct an A/B test with a purpose. This is a great way to gain sustainable insights that you can apply to future headline experiments.

ConversionXL wrote an extensive 6,000-word guide for A/B testing. They explain how to plan your site-wide A/B tests based on clear hypotheses and priorities. You can uncover and adapt their prioritization framework for email testing. Consider choosing variables such as personalization, capitalization, and more.

8. Go to your own inbox

As marketers, we sometimes forget the human impulses that drive people to open an email. Even classics like "What's in it for me?" can be overlooked after too many hours staring at a screen.

Refresh your memory by going to your own email inbox. Look at which promotional emails you actually clicked on. (Hint: If you've unsubscribed from all your mailing lists, now’s a good time to resubscribe.) With this technique, we’ve noticed that while cryptic headlines are fun to write, we won't be quick to open those. However, we will open emails when the subject lines make us laugh or announce a product launch or update.

9. Hey—be skeptical, okay?

To improve your email subject lines, you need to have a healthy dose of skepticism about stories of record-breaking examples. Yesware explains why in this cautionary talel about using the word “hey.” Yes, it yielded record-breaking results as a subject line for a famous fundraising email. But it also dragged down open rates in half a million sales emails.

You’re better off revisiting your own successes and examining open rates. Look at what has worked in the past and see how you can leverage that for future emails.

10. Improve your preview text

Sometimes, the subject line is nearly perfect, but it needs a little extra flair. Follow up with great preview text. As Phil Weltman from Klaviyo notes, you can probably do much better than the often-seen “Having trouble viewing this email? Click here to view it in a web browser.” Ideally, your preview text should complement your subject line, just like any other classic pairing, he adds. “Your preheader text should be the peanut butter to your subject line’s jelly—together, you use them to entice your reader to open the email.”

And if you still can’t find the perfect subject line…

You may need more than one. If you can’t figure out how to make that subject line work for everyone on your list, there’s likely a good reason for that. Your list probably consists of two or more different groups.

Instead of searching for the perfect one-size-fits-all headline, divide and conquer. Segment your list (just as a targeted email marketing expert would) and send emails to different segments with subject lines specifically tailored to them.