How to Create the Absolute Best Email Subject LInes

Written by Franco Varriano.

A great subject line is the most important part of your email. It’s what a headline is to a blog post. It’s the one chance you have to grab your recipient’s attention and stand out against the deluge of other emails crowding their inbox.

It’s worth spending the time to learn how to write great subject lines, and this is what this article will attempt to teach you. We can’t give you a surefire formula that works in all cases. But we can look at what tends to work, as well as what you should avoid. Best practices for email subject lines, if you will.

In today’s post, we’ll give you an overview of what does and doesn’t work when composing an email subject. By the end of this post, you’ll feel confident in your ability to start running your own email subject line experiments and reaping the reward of higher open rates.

An Experimental Mindset Is Key

Before we proceed with the nitty-gritty of good email subject lines, we want to talk a little bit about having the right. Despite what a Google search might indicate, there is no one formula for email subject line success. If there were, there’d only be one article on the subject and we could all go laughing all the way to the bank.

There cannot be a formula because every business case is different. The best subject line in a given industry for a given set of email subscribers will not work in another case.

Consequently, the best thing you can do to improve your email subject lines, open rates, conversion rates, and your email marketing, in general, is to test, test, test! Every email you send is a chance to test which types of subject lines work best. Don’t underestimate how much of a difference changing one word can make.

Along the same lines, you should also write at least 10 subject line ideas for every email you send. The subject line really is that important, perhaps more important than the content of the email itself. Invest the time into brainstorming 10 subject lines. Your first couple ideas will not always be your best.

Now that we’ve emphasized the importance of an experimental mindset, we can explore five different approaches to writing subject lines for high email open rates.

1. Curiosity

People are much more likely to open an email with an intriguing subject line. Humans are naturally curious, so much so that we’ll defy common sense and logic just to satisfy our curiosity.

Looking through my own inbox, here’s an example of a subject line that leverages curiosity. For those of you who aren’t familiar, Codecademy is a website that teaches you to program through interactive tutorials.

I opened this email just to see why the folks at Codecademy thought Python (a programming language) was so important to learn, even though I haven’t really considered learning it myself. This subject line uses a “Why we’re doing X” structure, one that can work quite well for drawing people in. It works because it offers an answer to an implied question (“Why are you doing X?). It’s also a structure that works for social proof-based subject lines, as we’ll see below.

2. Scarcity

Scarcity is a powerful marketing tool. Due to having evolved in a world where food and other essential resources were scarce, humans naturally want what’s in short supply. This make scarcity an effective basis for subject lines in the right situations.

Do be cautious, as it’s easy to overuse scarcity. Scarcity works best when credible. That means using scarcity in situations where it actually exists. It could be a closeout sale on a discontinued product, or admission to a coaching program with limited spots. In both of these cases, scarcity is inherent in the product and therefore makes sense. Using scarcity to sell a SaaS license, however, would make less sense because the inherent nature of SaaS is its infinite scalability. You can still do it, of course, but expect that your results may vary.

To see scarcity in action, check out this subject line from Target:

Now, this flash sale is a bit fishy given there isn’t any inherent scarcity in what they’re selling. But it’s still a compelling subject. I didn’t buy the curtains, but similar subject lines with phrases like “Last chance” or “Ends on X DAY” have gotten me to buy. This tactic works very well when combined with a compelling, personalized offer (more on that below).

3. Social Proof

Humans are deeply social creatures, and this affects every aspect of our behavior, including what behaviors are appropriate in a given situation. When we’re not sure how to act, we look to what others are doing to give us a clue. This is social proof, and it can work wonders in marketing.

How you use social proof in email subject lines will depend on what you’re selling. Pulling a short quote verbatim from a customer review or testimonial can be an effective approach, as can a statistic from a survey (“90% of user surveyed would recommend our product to a friend”).

For a look at social proof in email subject lines, here’s an email from Free Code Camp:

This is a subtle but powerful use of social proof. It plays off of curiosity as well (“What made it possible for these people to get jobs as ‘older’ developers?”), but the social proof is there in the promised stories, stories that lend credibility to Free Code Camp as a learning platform.

4. Brevity

Sometimes, less is more when it comes to subject lines. In an inbox full of verbose, pie in the sky offers, it can be refreshing to come across a subject line with just one or two words. To see this in action, let’s look at an email from the website No Meat Athlete (for context, this is part of an email sequence promoting one of the author’s vegetarian recipe books):

This email works especially well since it’s part of a longer series. Indeed, it’s the final email he sends as part of selling this book. You want people to pay special attention to sales-oriented emails like this, especially ones aiming to convince people on the fence about making a purchase. In situations like these, a concise subject line can be just the thing to get them to open the email and take in your persuasive copy.

5. Great Offers

At the core of successful sales-oriented emails is a great offer. Everyone wants to get a deal, after all. It’s not always the best approach to come right out with the deal in the subject line (see “Curiosity”), but it’s a powerful approach. Especially if you are offering a compelling deal, put it out there from the start.

As an example, here’s an irresistible offer from personal finance management app Mint:

Who doesn’t want free money? That’s what Mint is offering in this subject line. If you’re in a position to give someone a great deal, tell them. Don’t beat around the bush.

6. Personalization

Finally, we have personalization. This approach can lead to some of the most compelling headlines out there. You can give someone a customized offer based on their purchase history, location, age, profession, or interests they have expressed.

Groupon is the quintessential example of email personalization done well, but I thought I’d go with a different example for this article. Here’s an email from personalized based on location:

For a site like Meetup, this kind of personalization is easy and automated based on given location and stated interests. It’s also sensible — people only care about Meetups that are near where they live. Anytime you can personalize an offer, do it. It doesn’t have to be on a person-by-person basis. Even just customizing your subject line for different segments of your email list can do the trick.

Caveat: don’t use the recipient’s name in the subject line. This is such an overused tactic now that it can appear spammy and get people to skip your email. You’re better off using one of the other personalizations we discussed.

Send More Effective Emails with Less Work

We hope you now have a better understanding of how to write email subject lines that lead to opens. As we said in the introduction, there’s no one formula to rule them all — you have to do your own tests for your own unique situation.

When it comes to other aspects of email marketing automation, however, there are simple formulas to make things easier. is full of such formulas. Rare makes it easy to start using automated email campaigns for common challenges such as Welcome Series, Abandoned Carts, Order Follow-ups, and more!

Learn more about our powerful email marketing automation features or go ahead and get started right away by clicking the button below.

And if you’re one of the thousands of merchants who are already using Rare’s Smart Email Marketing software and want to see how our Customer Success Team can work with your brand to grow your revenue – feel free to book a call at your convenience here.

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