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How to Write Effective Email Subject Lines (Best Practices)

Do you read every single email you get?

If you are not a highly-driven reading addict, it is quite possible that you don’t. There might be many emails you leave unopened or send straight to the bin.

What do you think is it that attracts you enough to open an email and intend to read it?

Read on to see the 11 best practices on how to write effective email subject lines that will intrigue your intended audience into opening and engaging with your campaigns.

Key Takeaways

  • An effective email subject line maximises email open rates and captures the recipient’s attention. As the first impression of your email, subject lines play a pivotal role in determining whether it will be opened or overlooked.
  • A compelling subject line not only grabs the recipient’s attention but also sparks their curiosity and provides a compelling reason to open your email. Conversely, a weak or uninteresting subject line may result in your email being ignored, deleted, or even marked as spam.
  • By optimising your email subject lines, you significantly enhance the likelihood of your emails being opened, read, and engaged with, ultimately driving the recipient towards desired actions. 

What Are the Two Purposes of Good Email Subject Lines?

A good email subject line serves two primary purposes:

  • Email subject lines are the recipient’s first impression of your email, so it’s up to an effective subject line to grab attention and pique curiosity.
  • Following this, a good subject line is the determining factor in whether someone will open your email.

A weak, uninteresting or unrelated email subject line may lead the recipient to ignore your email, delete it, or even mark it as spam. By optimising your email subject lines, you can increase the chances of your emails being opened, read, and engaged or eventually leading the recipient into taking action.

10 Tips on How to Write Good Email Subject Lines

1. Know Your Audience

That’s the first rule of marketing—knowing who you’re talking to. 

Without knowing who your targeted audience is, there’s no way you can understand their desires, needs, struggles, and how to address and approach them.

Knowing who you’re addressing and why will help you craft more effective subject lines while saving you from wasting time and resources.

2. Don’t Mislead, Don’t Be Spammy, Don’t Be Clickbaity

Making false promises or giving out misinformation in your email subject lines is a sure way to ruin a good relationship with your customers and end up in the spam folder. Not to mention that you might encounter soaring unsubscribe rates.

Spam filters consistently examine certain indicators that suggest an email could be spam and typically search for suspicious language associated with scams and schemes.

Exaggerated use of exclamation marks (!!!!!), outlandish claims and promises (100% guaranteed, earn £100 million in one hour), excessive use of currency signs, and specific word choices often used in scammy contexts (no hidden charges) are some of the examples that might earn you a place in the spam folder and ruin your email sender’s reputation.

3. Set the Expectations Right with Clear Subject Lines

A clear email subject line helps the recipient quickly understand what the email is about and what they should expect to find inside. It is more likely to be read and understood than one that is vague, complex and confusing.

Your email subject line should convey clearly what the email is about. Avoid using vague or ambiguous language that could confuse or mislead the recipient. Making what to expect from the email’s content clear with the right subject line will go a long way in building trust in your audience.

4. Keep Your Subject Lines Short and Sweet

Here’s what you should know about email marketing:

  • You have about 1-2 seconds to grab the recipients’ attention with your subject line.
  • Email clients like Gmail, Yahoo, and Outlook put default character limits to how much of the subject lines they’re showing.
  • Mobile devices allow for even shorter subject lines due to smaller screen sizes.

So, as with clarity, shortness is a must for effective email subject lines.

Of course, you can check your campaign reports to see what your target audience uses to optimise your subject line lengths accordingly. But considering that 41% of email campaign views are from mobile devices, it’s best to stick to shorter email subject lines.

5. Show Your Brand’s Personality

It’s crucial to have a clear understanding of your brand’s tone of voice before getting to crafting your subject lines.

The tone employed in communication plays a pivotal role, and deviating from the expected tone can jeopardise the brand-customer relationship and potentially result in a loss of future business.

Conversely, maintaining a clear and consistent tone that aligns with your brand image and meets customer expectations fosters a lasting relationship. This approach to writing email subject lines ensures ongoing engagement and satisfaction for both parties involved.

6. Use Emojis Carefully

Using emojis in your email subject lines can be fun and help you grab attention in those overcrowded inboxes. However, there’s a catch. Using emojis in your subject lines can cause problems if:

  • There’s inconsistent rendering across devices and platforms.
  • Your target audience doesn’t care for them or, worse, dislikes them heavily.
  • They are irrelevant to the topic or just vague and difficult to understand.
  • They have a second meaning, and you did not mean to use them like that (yes, we’re talking about the eggplant emoji).

Don’t let these discourage you from ever using emojis, though. They are handy for keeping the subject line short when used at the right subject line at the right time.

7. Ask Questions?

Questions naturally stimulate curiosity and encourage recipients to open the email to find the answer. Additionally, questions can help to establish a sense of relevance by addressing the recipient’s needs or interests. 

At the risk of sounding like a broken record, it is important to ensure that the question is relevant to the content of the email.

Don’t be that person; don’t deceive people with clickbait. It can work and make the recipient open the link for once, but you do not want an annoyed audience that will mark you as spam and won’t read another email from you. 

8. Use Numbers and Listicles

Including specific numbers, such as percentages or quantities, makes a subject line more eye-catching and conveys a sense of importance. Meanwhile, using lists can help organise your content and make it easier for readers to understand the main point of your message quickly.

“The Best Tips to Improve Your Email Marketing Performance”

“Your Black Friday Email Marketing Strategy in 8 Steps 👑”

Which of these two subject lines would you most like to open? 

Most people would choose the one with the number because it tells the reader what to expect from the email’s content.

Depending on your industry, brand, and the purpose of the emails, you can use numbers in the subject lines in different ways. In eCommerce, numbers in subject lines are used heavily to promote sales like Ubisoft is doing this example:

Promotional marketing email from Ubisoft Store. The email subject line is “Save up to 75% during Black Friday Sale!”.

Or look at this newsletter from the singer-songwriter Lorde, where she is celebrating and reminiscing about the 10th anniversary of her debut album:

Newsletter from the singer-songwriter Lorde. The email subject line is “Pure Heroine turns 10”.

All in all, email subject lines with hard numbers are likely to get more engagement and increase the chances of your emails being opened and read.

9. Personalise (But Don’t Overuse)

Personalised emails are a great way to ensure you strike a chord with your audience and leave a lasting impression.

How do you personalise email subject lines?

Simple. You just need to use the data fields to use the personal information you have about the customer, which they have given you willingly and knowingly. We’re talking about their name, location, purchasing or browsing history, preferences, etc.

Incorporating personalisation in the subject lines is a great way to get the audience’s attention if it’s actually useful for the recipient.

Let’s say you are a platform selling event tickets, and there’s a ballet festival happening in London. You send an email to users in the area telling them about this not-to-miss event happening in their city. Now, someone can take their lover on a date or go with their music-lover grandma.

Personalised emails like the one above work because it’s focused on considering the context. The chances of someone living in Berlin caring about a ballet festival in London are low. In other words, this context requires personalisation.

So what do we mean by “don’t overuse personalisation”?

But suppose you use personalised subject lines for every single email you send. In that case, people are going to get used to this strategy and get frustrated. Consider using the recipient’s name in the subject line.

In real-life conversations, we say someone’s name if we want their undivided attention. But if you keep saying their name every time you see them, you become “the office weirdo”. It’s annoying at best and creepy at worst.

Beware of the context and what you’re trying to achieve.

10. A/B Test Your Subject Lines

If knowing who you’re talking to is the first rule of marketing, then always running A/B tests is the second rule.

Different customer segments respond differently, trends change, and what works today may not work tomorrow. The only way to know your subject lines’ effectiveness is by running split tests.

By split testing your email subject lines, you can determine which email subject line is more effective at capturing the reader’s attention and leading them to open the mail.

You can start testing your email subject lines with these:

  • Varying subject line lengths
  • With emojis vs without emojis
  • Numbers at the beginning vs at the end
  • Capitalisation
  • Punctuations
  • The tone of voice (matter-of-factly vs. witty)

A/B testing email subject lines will help you gain insight into what stimulates and resonates with your audience and optimise your messaging strategy.

Maximise Impact with Preview Texts

While subject lines have character limits, the power of preview texts should not be overlooked. These brief descriptors complement your subject lines, offering a unique opportunity to extend your message beyond limits.

Look at this email from Retail Sector and tell me honestly if you would open it. I know I didn’t.

Email subject line is “Kingfisher lowers profit guidance amid slight sales drop”. The preview text that can be seen on the screen is “This email is best viewed in modern bro…”

“This email is best viewed in modern browser-based email clients.” is not the way to convince someone to read your email.

Now, look at this example from Think with Google:

Email subject line is “How AI-powered ads drive growth”. The preview text is “Google’s GM of Ads gives a preview”.

The subject line tells me it’s about AI and online advertising, and the preview text tells me Google’s own General Manager of Ads will explain how it works. Together, they give the context and tell me all I need to know to open the email. It’s simple, and it’s good.

Now That You Know How to Write Good Email Subject Lines

Armed with these insights, take a proactive step in enhancing your email campaigns. Experiment with the provided tips, tailor them to your unique audience and observe the responses. Remember, the key lies in briefness, intrigue, and relevance to your content. 

With regular practice, you’ll get the hang of creating attention-grabbing subject lines that boost the success of your email campaigns.

Editor’s Note: This article was originally published on May 31, 2023, and was updated for accuracy and comprehensiveness on November 22, 2023.

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