Illustration of marketers delivering email subject line best practices to customers

Email Subject Line Best Practices + Sample Subject Lines

Subject lines drive opens. Without opens, your customer communications and program promotions simply won’t make an impression or accomplish your goals. To ensure success and boost open rates, follow these email subject line best practices.

Tips For Building Successful Email Subject Lines

An effective email subject line will catch the attention of the recipient and inspire them to open the message to learn more. The most reliable ways to do this are to…

  1. Keep it short
  2. Don’t forget the preview text
  3. Don’t bury the lead
  4. Use actionable language and active verbs
  5. Incorporate recipient benefits and offers
  6. Try including numbers
  7. Match the message
  8. Use emojis sparingly
  9. Avoid all caps or special characters
  10. Test, test, test

1. Keep it short

How long should a subject line be in an email? Subject lines should be quick, clear and specific; the best length is 40 characters or fewer. Longer subject lines are often truncated because of mobile displays and screen settings. Your intended message could be unintelligible if you make it too long.

Try using the tool TestSubject to see how your email subject line and sender name look on the most popular mobile devices and email clients.

2. Don’t forget the preview text

While not technically a subject line, your preview text (also known as preheader text) is equally important and can help you grab attention and boost opens. Use it to convey additional information that expands on the subject line. Text length should range between 40 and 140 characters.

Screenshot example of sample subject lines

3. Don’t bury the lead

Put important words at the beginning of the subject line; catch the customer’s attention immediately. As mentioned above, subject lines are often clipped short on mobile devices. Don’t let the best part of your message go unseen.

4. Use action language

People are more likely to open emails when they see actionable, eye-catching words in the subject line. Check out this exhaustive list of action verbs for inspiration.

You can also leverage free online tools to test your subject lines. These tools analyze and offer suggestions for improvement, including possible action verbs.

5. Promote benefits

Speak directly to the customer’s interests or concerns: How would opening the email benefit them?Customers respond well to specific references to their situation; email subject lines with the words “you,” “your” and “about your” tend to perform well.

Screenshot example of sample subject lines

6. Include numbers

Include a promo code or dollar amount to catch attention. Subject lines such as “Save XX when you use promo code XXXXX” tend to improve open rates as well as CTOR.

Screenshot example of sample subject lines

7. Don’t use clickbait

Your subject line should match the contents of your email. Don’t try to trick recipients and boost opens only to disappoint them with your email message. This is a surefire way to be flagged for spam or lose subscribers.

8. Be careful with emojis

When should you use emojis in subject lines? Questline Digital’s data shows that most subject lines with emojis perform below the industry benchmark. While not always true, they should be used sparingly and with purpose.

9. Make it readable

Using unique text characters or different fonts may seem like it would help your message stand out. But using special Unicode characters makes subject lines unintelligible to users who rely on screen readers. This means your email is not accessible to all audiences.

Screenshot example of sample subject lines

10. Test, test, test

Email subject line best practices include A/B testing. This is when you send two versions of a subject line to a small sample group, measure open rate or CTOR performance, then deliver the “winning” subject line to the remaining mailing list. Through the consistent use of A/B testing over time, an energy utility can narrow down very specific best practices for customer segments. Some tips to keep in mind:

  • Is my sample size big enough? Typically, 500 to 1,000 recipients is an effective sample size and will deliver statistically meaningful results.
  • How long should the test run? More than50% of opens and clicks happen within the first 6 hours after email delivery. However, to eliminate seasonal and day-of-week variables, it’s best to test for one full week before determining a winner.
  • Is there a clear winner? Depending on the sample size, a good rule of thumb is to look for a 25% to 35% performance variance in order to declare a clear winner.

Sample Subject Lines for Energy Utilities

Let’s look at high-performing subject lines in action. We evaluated the top email sends for our energy utility clients and have compiled the best sample subject lines for your reference and inspiration.

Best subject line for promotion emails

Promotional emails, or those that sell products or promote programs, are often the hardest to get customers engaged with. People don’t typically enjoy being sold to. Your subject lines for promotion emails need to work hard to showcase benefits, inspire action and catch attention.

Chart listing best sample subject lines for email subject line best practices

Employing Email Subject Line Best Practices

Bookmark this blog and refer to our list of testing tools and sample subject lines the next time you’re building an email campaign. And remember to test, test, test!

Learn how Questline Digital’s engagement experts can boost the performance of your email marketing campaigns.