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Do you struggle to come up with great subject lines for your email campaigns?

The subject line is the start of the readers experience with your campaign, and in a world of increasing distractions, it can also be the end of their experience if you don’t make it captivating and engaging.

So to help you write a great subject line that engages your readers and gets your emails opened, here’s 8 subject line formulas that you can apply to your next email marketing campaign.

1. The question subject line

Questions make great email subject lines because they get the reader to think about how the subject matter applies to their own life.

The best questions will resonate with the reader and their past experiences, while arousing a sense of curiosity to learn more about the subject and whether their experiences are similar to others.

For example:

  • Do you check your emails when you first wake up in the morning?
  • Are you a zombie without your morning coffee as well?

These subjects lines work because the reader can relate to these behaviours, but are also drawn to click-through to possibly learn more about whether others have similar experiences and what the possible implications of that behaviour is.

2. The ‘How to’ subject line

There’s an old saying in copywriting circles that you can’t write a bad headline if it starts with the words ‘How to’.

The ‘How to’ subject line formula works so well because it forces you to describe the content of the email in very clear language. Take these 3 subject lines for example:

  • How to get better marketing results through beautiful design
  • How to win friends and influence people
  • How to get 1,000 new email subscribers in 1 day

By reading these subject lines, you know exactly what you are going to learn from opening the email.

The key to success with this subject line formula is focusing on the benefit. Nobody actually wants to learn another process or methodology, instead they want to get the end benefits of better marketing results or new email subscribers, so make sure when using a ‘How to’ subject line you focus on the benefits and not the process itself.

3. The scarcity subject line

Scarcity is a powerful driver of human behaviour. When something is in short supply, our fear of missing out kicks in and we are compelled to act.

Adding a time or availability limitation encourages readers to open and act on your email before it’s too late. For example:

  • Only 2 days left to get 50% off shoes
  • Hurry! Only 3 consultation spots left.
  • Get free shipping if you order within the next hour

The key to using scarcity in your email subject lines is importance. If the reader doesn’t have any intention of purchasing from you, they are not going to care that they can get free shipping if they purchase in the next hour. You need to make sure the offer you are presenting is important to the reader before you bring scarcity into it to try to compel them to act quicker, otherwise, the time or availability limitation you are imposing is irrelevant to them.


Get our guide to Creating High-Performing Email Campaigns and make every email you send a success. 

4. The announcement subject line

Using words like “Introducing” and “New” in your email subject line gives the reader a feeling that your email contains new, breaking information they haven’t heard yet.

In our recent study on power words in email subject lines, email subject lines that included terms like ‘Introducing’ and ‘New’ increased the chance of the email being opened by 9.45% and 3.26% respectively.

Examples of this formula in action include:

  • Introducing Canvas: A better way to send emails
  • Update to our iPhone App
  • See our new design gallery

By using words like ‘Introducing’ and ‘New’ in the subject line, you are letting people know that your email contains new information they don’t know yet and are encouraging people to open the email and learn more.

5. The number subject line

Using numbers in your email subject lines is a great way to set people’s expectations and provide a structure for the content of your email.

Every time we A/B test our blog post headlines, we find that the version of the headline containing the number outperforms the one that doesn’t. For example, when we A/B tested ‘3 steps to measuring the success of your email marketing with Google Analytics’ against ‘How to measure the success of your email marketing with Google Analytics’, the subject line with a number got a 57% increase in opens.

So where possible, use numbers to make your subject line more specific. For example:

  • 30 ways to build your email list
  • 3 steps to sending beautiful email campaigns with Canvas
  • 10 product announcement emails reviewed for conversion

The key to success with this formula is the number you use. If you are suggesting effort a reader needs to expend (like steps in a process for instance), then using a low number works better as it suggest the process is quicker and easier. However, if you are providing value to the reader (like a number of ways to increase email subscribers) then a higher number will work better as it increases the reader’s perception of the value your email will provide them.

6. The curiosity gap subject line

Viral websites like Buzzfeed have built publishing empires off the back of a psychological phenomenon known as the curiosity gap.

Professor George Loewenstein coined this term to describe the gap between what we know and what we want to know. When we notice a gap in our knowledge, it produces a feeling of deprivation that prompts us to go looking for that piece of missing information in order to stop feeling deprived.

However, curiosity requires a little bit of initial knowledge first. We’re not curious about something we know absolutely nothing about. However, as soon as we know even a little bit, our curiosity is piqued and we want to learn more.

So try leaving a small curiosity gap in your subject lines to encourage opens. For example:

  • Dave Richardson asks the most basic question ever, and stumps our smartest politicians
  • This little-known copywriting trick will increase your email click-through rate
  • 9 out of 10 Americans are completely wrong about this fact

As you can see, these subjects lines leave just enough information out to pique your curiousity. What is the question Dave asked? What’s the fact that 9 out of 10 Americans are wrong about? By piquing people’s curiosity, you provoke the sense of deprivation and compel them to open the email to learn more.

7. The surprise subject line

Everybody loves a good play on words or a pleasant surprise. In fact, studies on brain activity show that these unexpected occurrences light up the pleasure centers of the brain.

Whether it’s a small chuckle or an unexpected offer that benefits the user, using surprise in your subject line causes the reader to pause while scanning through their inbox and piques their curiosity enough to open the email and learn more.

Some examples include:

  • Warning: Unattended items in your shopping cart may be eaten by gnomes
  • What Elvis Presley can teach you about email marketing

The key here is not so much to use a specific formula, but just to surprise the reader with something they wouldn’t expect.

In fact, during Barack Obama’s presidential election campaign his team used the subject line ‘Join me for dinner?’ in one of their email campaigns. Whilst ‘Join me for Dinner’ is certainly not a surprising subject line, the fact that it came from the President of the United States certainly surprised a few people.

8. The personalized subject line

Working your subscriber’s name into the subject line of your email adds a personal touch that is likely to catch your reader’s eye. Any time you can make your reader feel like you’re connecting with them on a very personal level, it builds a sense of sincerity.

In fact, in our recent study on power words in subject lines we found that using the recipients first name in the subject line increased the chance of the email being opened by 14.68%.

This can be combined with some of the other formulas for maximum impact. For example:

  • John, are you a zombie without your morning coffee as well?
  • John, 9 out of 10 Americans are completely wrong about this fact.
  • John, there’s only 2 days left to get 50% off boots.

By including the subscriber’s first name, you create a feeling that you are speaking directly to them and give your email a sense of relevancy that encourages them to open it and consume the content.

In Conclusion

Your subject line is what entices your reader to open your email and pursue the information inside, so it’s important to put some serious thought into this portion of the writing process.

There are many ways to write an interesting, compelling subject line based around the few tips we’ve provided here. They key is to A/B test different types of subject lines to see which ones work best for your unique audience as it all comes down to what your audience is looking for in the emails they receive from you.

Your turn: What email subject line tactics get you to open and read emails? Are there some that completely turn you off from opening?

This blog provides general information and discussion about email marketing and related subjects. The content provided in this blog ("Content”), should not be construed as and is not intended to constitute financial, legal or tax advice. You should seek the advice of professionals prior to acting upon any information contained in the Content. All Content is provided strictly “as is” and we make no warranty or representation of any kind regarding the Content.
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