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Email Subject Line: the Secret Agent of Conversion

5 min read
Email Subject Line: the Secret Agent of Conversion

Have you ever wondered what influences the way emails are perceived by the recipient? How long should the email be? What kind of titles work best? Should you put graphics into the content? What should the footer look like?

So many questions, so few answers. Let’s try to look at each of them individually and find the ideal email recipe. In this article, I’ll tell you about writing a perfect email subject line and getting the most out of your campaigns.

To write or not to write – that is the question

Contrary to what some marketers may think, email is not dead, and the situation is not going to change soon. Research by Statista predicts that the number of sent and received emails will grow each year:

A bar chart from statista of the numer of emails sent and received worldwide between 2017-2022 in billions.

A recipe for a perfect email subject line

The first thing that readers see when they find an email in their mailbox is the email subject line. In the mailbox, there are hundreds of them, one after another, all lined up. So what should you do to stand out and become a unicorn among the flood of email subject lines? There are a few tactics you can use. Let’s take a look at some of the most popular ones:

Fear of missing out on something

From the psychological point of view, the risk of losing something that potentially belongs to you is more effective than the mere promise of getting something new. And if the customer feels that they may lose something valuable, the probability that they will open the email significantly increases. A great example of such a title is an Uber email campaign with the title “Grab a ride pass before they’re gone”.

Arouse curiosity

Have you ever read a book that you just couldn’t put down, one that kept you up late because you just had to know what happened next? The simple reason why you did it was curiosity. The same principle applies to opening emails. Sparking interest in the contents is key to getting it opened. Try to ask some provocative question. If your audience is laid back enough, you may even go crazy with something like “What do they eat in prison?”

Several catchy email titles promoting a fashion brand for inspiring your digital marketing activities and open rate.

Add some humor

Hey, we all like jokes, right? Remember, however, to adapt them to your recipients and certainly not to offend anyone. Choose a safe topic and go for a smile like Groupon did: “Hey… Were You Gonna Delete This?”

Embrace emojis

What can be more eye-catching than graphics in the text itself? To highlight your message, use some kind of visual element. Go a step further but also to enrich graphics with a simple animation.

An emoji animation eating the words of a subject line to add a catchy visual element and improve digital marketing metrics.

Use what has already been tested

Alchemy Worx has analyzed 24.6 billion emails and checked some keyword open rates. Here are their findings concerning the most effective verbs, nouns and adjectives:

  1. Upgrade
  2. Just
  3. Content
  4. Go
  5. Wonderful
  6. Jokes
  7. Promotional
  8. Congratulations
  9. Revision
  10. Forecast
  11. Snapshot
  12. Token
  13. Voluntary
  14. Monthly
  15. Deduction

Take this knowledge and feel free to use it in your email subject line 😊.

And… action!

Speaking of particular words, try to convince readers to take a specific action. The easiest way to achieve this is through the use of verbs.

Personalize wherever you can

It’s not just about using some formats with dynamic fields like: {firstname} + the rest of the subject line. Step into the shoes of the recipient of the sent email and try to determine what they will be interested in. It’s likely, for example, that they would like to make purchases in their neighborhood. If you have well-segmented customers, in terms of place of residence, try to use this knowledge in the title of the email.

For example, if you’re running a restaurant rating portal, try to send something like this: Eat out Boston! Best restaurants with burgers for lunch. This is an example of a greatly personalized message of this type – provided that the message recipients do not live in Warsaw, for instance.

A short counting lesson

One, two, three… or maybe a 10$ discount. Or a 40% off sale. Or 15 reasons to buy something. Using numbers makes your subject line clear and specific. They are definitely among the best practices for marketing subject lines.


As you can see, this idea doesn’t make any text look professional. If you write whole lines using nothing but capital letters, nothing will be highlighted (and the reader will not take you seriously). In fact, you’ll probably achieve the opposite effect.

Don’t ignore the preview

It’s hard to believe that so many companies still forget about this part. Let’s compare just two examples:

An example of an email subject line with preview text.

See the difference? In the first Presentation Panda example the preview text follows the subject. In the second one it doesn’t – and you have to admit that it doesn’t look inviting.

Write in the second person

Here’s another trick to make your content look more personal. By writing in this way, you give the impression of addressing the recipient directly, rather than sending an impersonal form to the entire contact database.

Quality, not quantity

When sending your first email campaigns you will probably make some mistakes in the subject lines. Remember, however, to draw conclusions from them for the future. Before you send them, check for typos and how they are displayed on different mobile devices. To get an idea of just how much the same message can vary across platforms, check out the comparison of email shown on iPhone (iOS) and Samsung (Android).

An email showing up on the screen of a Samsung and iPhone to show the difference in message display.

Wrapping up, or the power of words

I know—there are so many rules for such a small part of an email. You don’t have to do everything at once, though. Start by implementing one or two selected tips. The email subject line is not a Christmas tree, it doesn’t have to be as colorful and rich as possible and make the neighbors jealous. Let your competitors envy your ingenuity and the results you get without putting everything possible in one place.

Even if you write the funniest title you’ve ever seen, even if you added a number and an icon, you can still ruin everything by not checking for stylistic or spelling mistakes. Like they say, you only get one chance to make a first impression so don’t mess it up!

P.S. To conclude on a positive note, let’s go back to the subject of headlines of the 20th century.

XKCD did it and slightly “corrected” it using the principle of adding numbers, arousing curiosity, speaking in the second person, and using verbs encouraging to action. In other words, the whole post above in a humorous nutshell. Enjoy!