(This blog was fully revised in January 2024)

Email subject lines are mostly short, but they hugely impact your emails’ performance. A great subject line will help your email stand out in the inbox of your recipients and encourage them to open the email. 

The success of all your email campaigns begins with good email subject lines. Therefore, it’s important to know how to write a subject line, otherwise your campaign may never really take off.

So welcome to this article, where we discuss 8 ways to craft a great subject line.

But first a quick primer on what makes a good email subject line.

What makes a good email subject line?

There cannot be a subject line that’s a good fit for every email, every marketer, or every campaign. However, there are six elements that all good subject lines share, no matter what. 

Here goes:

1. Tantalizing yet balanced

Believe it or not, your subject line needs to do some ‘selling’.  That’s not in the sense of people paying you money to buy something in return. Here, ‘selling’ means convincing people to perform a certain action they’d have otherwise not taken.

In order to achieve that, your subject line should be tantalizing and attractive. It must create a certain desire in the minds of the recipient. 

But at the same time, it shouldn’t be excessive or over-the-top. Cheesy subject lines can either look unconvincing (‘Here’s how to earn $3K in 2 hours!’), or they may even be alert spam filters. Don’t exaggerate to the point of becoming dishonest. For instance, if you’re offering just 5% off your regular prices, you shouldn’t say it’s the discount offer of the decade.

2. Bias for action

A good subject line propels the subscriber toward action. Typically, the action isn’t to buy something, it’s to open and read the entire email. And for that, your subject line should carry a phrase or two that clearly indicates urgency.

3. Optimized for customization 

You have a lot of data and insights about your subscribers today – perhaps more than you realize. Those analytics can hugely help the way you write your emails, so that every subscriber feels that the email has been written for them.

One of the easiest ways to personalize the email subject line is to use the most recent action or achievement of the subscriber. For instance, the below example uses the comments a subscriber received against their answers on a forum.

4. Start of a good story

You’ve probably heard it a dozen times, but we’ll repeat it because it’s important: humans are hardwired for stories. Which is why writing and storytelling have become important skills in the current age.

The below subject line has excellent scope, because the story can go anywhere: Belinda could talk about her third-grade teacher Miss Writebird, the kindly neighbor Mr Applepen, the intriguing stranger she met while returning from the high-school prom, the lovely baseball glove her grandfather left for her, the wily local politician Mr Mean, her first day at the non-credit course in Egyptology she took at university….

You see how many options exist?

All of them can be the beginning of a beautiful story that served as her first copy tip.

5. Contextual and useful

At the start of every year, marketers, hiring managers, investors, suppliers, and pretty much everyone else, look forward to understanding what the new year holds for them. The below subject line is one good example of context: The email was sent on 29 December 2023 and promises to talk about the trends of 2024.

That makes the email subject line not only contextual but also something of value.

6. Interesting and engaging: 

Does your email subject line arouse curiosity? If yes, you have a winner on your hands. That’s because humans are wired to satisfy their curiosity. 

Which means most of us can’t rest unless we’ve been able to find out what’s hiding behind the few simple words. And marketers use it intelligently to drive marketing. As a matter of fact, there’s an actual term for it: curiosity marketing.

Below is a great example of how to leverage human curiosity and make people want to open your email.

8 Rules for powerful subject lines

So what goes into making a great subject-line that will almost always get fantastic results? Although there is no magic, there are some vital aspects of the subject-line which can strongly influence the open rates. So here are 8 powerful rules:

1. Make it precisely vague

Think of the subject line as a fence around a beautiful home you’re trying to sell: short enough to hint at what a lovely property lies beyond, but high enough to not expose everything. That way, more prospects would be willing to come in and look around, rather than pass your house by.

You could use a little bit of suspense or a touch of exclusivity. You may make your subject lines carry that air of mystery that’d make subscribers open the emails.

Finally, the length. Most email clients (e.g. Yahoo, Gmail) cut off the subject line at around 55-60 characters. And mobile phones will slash your subject line after the first 30 characters. 

Estimates vary a bit, but anywhere between 49% to 81% emails are opened on mobile phones, so you want to pay attention to how your subject line is displayed on mobile devices.

2. Focus on personalization

We don’t need to tell you this; just look at the number of emails sitting in your inbox, unopened and almost ignored. Now look at the emails you’ve opened. Finally, compare the two.

No prizes for guessing: emails with personalized subject lines end up with a much better open rate. A study suggests “emails with personalized subject lines get a 26% boost in open rates”.

See how the above personalized subject line is unique? Instead of using the standard tools for personalization (e.g. gender or purchase history), it focuses on how they can solve my problem. 

Weaver has a program where she teaches copywriting, and The Ink is the name they use. This email offers to help me figure out whether I should join – and that too in just 2 minutes.

If the sender is offering to solve my problem so easily, what more personalization can I ask for? 

3. Be mindful of who’s sending

Yes, we know it’s you who’s sending. But who is this you? Is it donotreply[at]domain[dot]com? Is it qrcc123[at]domain[dot]com? Or perhaps newsletters[at]domain[dot]com?

If you use any of the above, it’s time to reconsider. Here’s why.

1. The sender address is donotreply[at]domain[dot]com: This sending address is a little discouraging and impersonal. The sender wants to write emails to you, but doesn’t want to hear back from you.

However, in some cases this address is unavoidable. As far as possible, use this to send temporary codes and OTP.

2. The sender address is newsletters[at]domain[dot]com or hello[at]: This sounds a bit impersonal. Makes one think of a faceless person in a big enterprise that doesn’t care about its customers. However, a corporate entity cannot always escape this, so it’s a bit of a compromise.

4. Keep away from spammy language

Here are a few big no-nos when you’re crafting an efficient email subject line. Keep away from

• Using all caps (“A WONDERFUL OPPORTUNITY FOR YOU”)
• Including too many exclamation marks (“Too many roses?!!! 4 reasons why!!! And a secret!!!”)
• Having weird characters (“Tough times @#$ ? No worries, say C#@$’)
• Making a promise to make big money (“Make $$$ while you sleep! The trick to earn big!”)
• Adding words that can activate spam-filters (“Credit card loan? Payday loans? Forget interest!”)

Remember, the anti-spam filters are only getting more aggressive. So if your email subject line gives them the slightest reason to flag your email as spam, chances are your email would land in the spam folder only.

It’s important that your emails don’t face serious deliverability issues, otherwise your marketing campaign will fail. It is, therefore, important that you verify email list and remove all undeliverable addresses.

5. Use a conversational tone

One of the best things to do would be to establish a tone that’s both casual and official. A subject line can become engaging if you use a regular conversational tone. For instance, “Would you like the opportunity to sample our new line of ketchups?” is a bit too formal – I mean, who talks like this?

Against that, a subject line like, “Ketchups anyone?” is not only shorter but also a great deal more real-life, more conversational. That’s like how people speak. Try writing your subject lines this way.

The example above uses that informal style, it’s like Henderson is seated across the table from me and is talking about something that’s painful. Totally relatable.

6. Try meaningful questions

Questions are a great point to begin a conversation, and if you’re wondering how to draft a great subject line, try using questions.

There are three aspects of questions that contribute to a click-worthy subject line. One, the question is an incomplete piece of information. Hence, it arouses curiosity. Second, there’s a hidden promise of what information you’re about to share. And three, a compelling question will reflect the pain point of the subscriber. That’s a great way to make them click and open your email.

In the above example, Henneke uses just two words (“Distracted readers?”) to reflect one of the most important questions marketers the world over are battling with: reduced attention span. See what a powerful hook it is?

And it has a hint of “This is how it needs to be done.” and there’s a subtle hint of what action you’ll need to take next.

7. Sell by offering help

The two examples below illustrate an important point. 

Gagan’s subject line makes a great promise for something that’s very promising. We don’t know: Gagan might be selling or promoting a course, or maybe sharing some free resources. But we do know one thing: anyone with the slightest interest in AI is definitely going to open the email after reading this subject line.

Brittnee’s email is slightly risky. The number they mention ($551,000) is obviously too high to appear believable. Who knows, it might like one of those jokes you read every Christmas or every Black Friday: Here’s a quick tip to save $3,000 this Christmas – delete your shopping app!

However, the subject line also says it’s not a clickbait. Which means there’s something of real value behind this enticing subject line. We don’t know about you, but we are not going to give this subject line a miss.

8. Humour has its own place, but…

The good part of humor is that people enjoy it, whether they’re your customers or not. The downside? It’s often very contextual.

What’s smart for you could be edgy for others (The record-breaking game Candy Crush took it close to the edge when, in an ad, it said: The game version of pure cocaine). 

What’s obvious for you is lost on others, because the cultural context is missing for them (e.g. the famous dope running for an important political position in your country may mean little to someone from across the globe).

And of course, humor in subject lines is tricky because of length: subject lines are short. If you are confident that you can pack humor that transcends geographies and cultures, and that too with no more than 60 characters, well, go ahead.

The above email by Tim Denning is a good example. For some, the humor is entirely lost, while for others it brings a smile on their face with the obvious exaggeration (or the low probability of this being true). And for still some others, it’s interesting at another level.

This post doesn’t cover everything you need to know about subject lines, but it does cover all the major issues.

Wish you great luck in your next email campaign!

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