5 Email Subject Lines Best Practices to Supercharge Open Rates


Written by Franco Varriano.

It can be hard to overemphasize how important email subject lines are to your email marketing campaigns. After all, these short snippets of writing are only read for a few seconds. How impactful can they really be?

Very impactful. Each subject line sends an important signal to your readers. Are you scammy and pushy? Or are you adding value in a friendly way?

Crafting the right email subject line is tricky because many of the nuances are easy to overlook. And there’s no one-size-fits-all approach.

For instance, there are many different ways to create great email subject lines, and we’ve already given you plenty of great subject line examples. But there are certain universal rules that you must follow if you want to have the most email marketing success – best practices, if you will.

So today, we’re going to explain email subject lines best practices. By understanding and applying these simple strategies, you’ll build trust and credibility with your readers, boost your email open rates, and turn more readers into paying customers.

1. Focus on Your Audience

The fastest way to get your email deleted is to write a subject line that’s selling a product to someone who doesn’t want it.

You’re writing these emails for your readers, so make that clear. They should be excited to see your email after reading the subject line.

There are a few ways to make sure this happens:

  • Know your audience. You need to understand your readers’ dreams and burning pains. Why did they subscribe to your email list? How can you improve their lives?
  • Add value. Once you know how you can serve your audience, you need to actually do it. Send emails that get them closer to solving their problems and achieving their goals.
  • Tell, don’t sell. You may have the best facial cream on the market, but you don’t want to ask your readers to buy it in the subject line. Instead, tell them the benefits with concise language. For example, “Clear your skin and make it glow.” You can sell the product in the actual email.

In addition to getting your emails opened, this will build trust with your email subscribers. They’ll appreciate that you’re only sending emails that potentially interest them and will stick around much longer because of it.

Check out how Aritzia uses fresh, age-appropriate language to appeal to their female, millennial audience:

The best email subject lines focus on the reader. If you know what your customers want, give them value, and don’t try to sell to them in the subject lines, you give your emails a good chance of being read.

2. Remember Your Goals

You may need to focus on the reader, but you can’t forget what you want to accomplish with your email. Every email needs to have a specific call-to-action that your subject line prepares them for it.

So, before you write the subject line of your promotional email, you need to know the email’s purpose. Do you want readers to click through to a sales page? Do you want to send them to your website? Or do you want them to respond with feedback?

Once you know the purpose of your email, you need to hint at it in your subject line. But you don’t need to specify the exact call-to-action. You can mention the benefits in the subject line and let your call-to-action show them how to obtain those benefits in the email body. For example, your subject line might be, “A proven system for making friends,” and your email’s call-to-action can send them to a sales page that sells the system.

Also, people are more likely to take action (and open your email) when you start the subject line with a strong verb. For example, “Find new friends this afternoon” is more enticing than, “How to find new friends.” People need to be pushed to action without feeling like you’re taking advantage of them, and that’s exactly what a good verb does.

Check out how Canva seamlessly makes the link between their subject line and their desired call-to-action. Now that’s some easy-to-swallow copy!

A great subject line strategy always has a clear goal. In addition to having more emails read, guiding the reader toward your desired action will get you much better click rates with your email marketing campaigns.

3. Craft Compelling Headlines

An effective email subject line captures the reader’s attention and piques their interest to see more. It may seem difficult, but there are six different tactics you can use to create the perfect subject line for your readers.


Think about gossip for a second. Movie and television stories are often written around gossip. Even in real life, gossip only carries an intense stigma because people can’t keep their mouths shut.

But gossip is only important because people are curious. When they realize that someone has interesting information that they don’t know, they immediately want to know what it is. It drives them crazy if they don’t find out.

You don’t need to be dramatic, but you want to pique the reader’s curiosity. Do this by hinting at the contents of your email body.

“This is how we doubled revenue in 8 months…”

Make the reader curious and it’ll be hard for them to not click into your email. Giles Thomas of AcquireConvert does a great job in the email subject line pictured below by bating the reader with the strong word “deadly” and the mysterious word “myth”. Each of these words incites curiosity and encourages the reader to click.


Adding scarcity or urgency to your subject line can create an innate desire in your customer. Have you ever heard of FOMO – the fear of missing out? Humans are psychologically wired to act if they believe the opportunity will disappear.

Scarcity is usually demonstrated with a limited supply of products or and limited number of openings for a service. And urgency is commonly used during product launches that are only open for a set amount of time. But you can get creative because there are many other ways you can use them.

Be careful though – your email subscribers are smart. If you’re trying to deceive them or sell them something they don’t want, you’ll quickly lose their trust and their email address.

Here’s an example of urgency at play, where ecommerce store Horse Lane uses a “last chance” in their abandon cart email to  urge customer to return to cart and buy:

Limit the benefits you have to offer and your customers will be much more compelled to take action.

Social Proof

When we don’t know how to behave in a particular situation, we look to the people around us for guidance. This is the principle of social proof, and you can use it to powerful effect in writing your email subject lines.

Here are a few ways you can use social proof to make your subject lines more compelling:

1. Mention a celebrity or expert. The skin product Beyoncé uses to stay young. Or The product Richard Branson, Elon Musk, and Mark Cuban can’t stop talking about.

2. Quote customer statistics. Join the 400,001 moms who already use our meal plans. Or Why 31,211 people would recommend our succulent cultivation course to a friend.

3. Media coverage. Our product featured in the New York Times. Or Consumer Reports rates our product most durable on the market.

4. Customer ratings. Our customers consistently give our product 5 stars. Or Users give our product two thumbs up.

5. Case studies. Learn how our product changed this single dad’s life. Or Why this one Ontario man uses our product every day.

6. Brand association. Why Facebook requires everyone on their team to use our product. Or How our product transformed the way Berkshire Hathaway operates.

7. Financial information. How our product generated an extra $40,011 per year for this small business. Or How switching to our product saved this family $105 per month (these also make great case studies).

You can also combine any of the above for extra impact, provided of course that the information is true. Blue Apron uses the celebrity mention technique to entice readers:


The maxim less is more applies just as much to subject lines as it does to the design of your online store. The shorter you can make your subject lines, the better. This is true for a few reasons:

1. Email Apps Limit the Number of Characters Displayed

Whether it’s in Gmail, Outlook, or Apple Mail, your subscribers can only see a limited number of characters in your subject line. The precise amount depends on the email app in question, and whether your subscribers are viewing email on their mobile device or desktop.

You should always assume, however, that customers will be on a mobile device (especially since 3 in 5 consumers check email on their mobile devices, according to a report from Fluent).

2. People Check Email in a Hurry

While it’s nice to imagine your subscribers eagerly awaiting the arrival of your latest marketing email, we all know the reality is different. People check their email while waiting in line at the grocery store, on the toilet, and in between meetings. They don’t have time for subject lines that meander on and on without getting straight to the point.

Keep your subject line brief, and you’ll have a chance of getting through.

3. People Receive Huge Amounts of Email

According to data from DMR, the average office worker receives 121 emails per day. Your email is just one drop in the deluge of email overwhelming the average person. Because of this, a brief subject line is best for cutting through the noise (when combined with the other tips in this article, of course).

So how long should your subject line be, exactly? According to a report from MarketingSherpa, the ideal subject line length is between 41 and 50 characters, based on the read rate of 9,313,885 emails from more than 3,000 retail senders. That being said, the report acknowledges that it’s important to experiment with length and not be afraid to use a longer subject line if the offer merits it.

Great Offers

The concept of an “offer” is as old as the art of selling itself. It’s easy to get so wrapped up in the details of word choice, headline length, and statistics that we forget about what we’re actually selling. Crafting a great offer should come before any of the writing you do. If you don’t have something compelling to offer your subscribers, you’re better off not sending an email to begin with.

So what do great offers look like? Here are a few ideas to get you started:

1. Free

Everyone loves free stuff. Just having the word “free” in your subject line is compelling by itself. Try phrases like “Free Shipping”, “Free Training”, or a “Free Gift”.

2. Discounts

If free is the best, then discount is a close second. People enjoy feeling like they’re getting a deal, and discounts promote this feeling. The classic way to phrase a discount is using a percentage, as in “25% percent off sweaters”. But you can also use some other retail classics like “Buy one get one half off” or “Buy one get one free” (known as BOGO for short).

3. Bundles

Similar to discounts, bundles involve combining certain products that go well together and selling them at a discount. So, for example, if you sell record players and record player accessories, you could offer to throw in the accessories for free when someone buys a record player of a certain cost.


Whom would you rather buy from? A trusted friend who knows what you like (and never forgets your birthday)? Or a faceless company that addresses you with “To whom it may concern”?

The answer is clear, and this is why it’s so important to personalize your subject lines. How do you go about this? Here are a few steps you can take to ensure a personalized, customized experience for each of your subscribers:

1. Segment Your Email List

If you’re not segmenting your email list, you’re missing a chance to provide customers with the offers they’ll love. When you segment your email list, you divide the list into different groups based on data your customers provide. Common forms of segmentation include purchase history, age, responses to surveys, and time since last purchase.

Once you’ve decided how you’ll segment your list, you can then create custom subject lines for each segment in order to increase the likelihood that they will make a purchase. For example, you’d want to use a very different subject line for a first-time customer than for someone who hasn’t bought from you in a couple months. Rare makes this easy with its advanced customer segmentation.

2. Make Customers Feel Special

We all want to feel special, so use that to your advantage when writing subject lines. Don’t just say “Dear Customer”; say “For our favorite customers only”. Send a gift such as a discount or free item on the customer’s birthday.

You want to make your subject lines feel like an email from someone who “gets them”, from someone they can trust and who is looking out for their best interests.

We should also mention a common form of personalization that can have the opposite desired effect. Using the customer’s name in the subject line has become the norm ever since email technology has made it possible to automatically insert it at any point in the email. This has now become so common, however, that customers have become desensitized to it. We recommend avoiding it and instead focusing on personalizations related to your offer.

3. Localize Your Offers

One of the defining features of brick and mortar stores is that they’re particular to a location. The customer associates them with their town. This is harder to do in ecommerce, but not impossible. You can localize your offers to your customer’s country, state, or even city. This will make them feel special and is also a good way to stand out amid the other emails in their inbox.

Airbnb are masters of this technique. They send emails based on your browsing history and home city, using phrases such as “Weekend getaways near Nashville” or “Explore Chicago with these experiences”.

You can do the same with your online store, offering promotions related to local holidays, the weather in your customer’s location, or even custom merchandise just for where they live.

4. Avoid These Trust-Destroying Practices

We’ve spent most of this post discussing what you should do to create a compelling email subject line, but we also need to cover a few practices to avoid. Never do any of the following things in your email subject lines:


Using “FW:” or “RE:” in your email subject destroys trust and credibility. This tactic may fool a customer once, but after that they’re likely going to unsubscribe or add your sending address to their spam filters. Don’t fool customers; present them with a genuine, compelling offer.


We’ve all been fooled by a headline for an article or email that claimed something crazy but then turned out to just be an exaggeration. It’s a disappointing, frustrating feeling when someone lies to you in that way, and those aren’t feelings you want customers to associate with your brand or marketing communications.

Never write a subject line that claims something is in your email when it isn’t. Just like cheating, it might work once, but it will hurt your business in the long run. Instead, spend your time coming up with an offer so excellent that customers will be delighted to open your email and find out that it’s not too good to be true.

Looking Spammy

Getting stuck in the spam filters will be the death of your email marketing. We can’t guarantee some of your messages won’t end up in spam, but we can tell you how to avoid writing subject lines that look spammy.

First, never USE ALL CAPS for your subject lines. Not only is this a common hallmark of spam, but it looks aggressive and pushy to your subscribers. It’s okay to use it for one word occasionally, but in general, you should avoid it.

Second, don’t use multiple exclamation points. One is fine, but only once in a while and in a case where it makes sense. Exclamation points also look pushy and frantic, which is not an image you want to project. If your offer is high quality, then you won’t need exclamation points to emphasize it.

5. Test and Track

All of the things we’ve discussed in this article are best practices to get you started. The actual best practices are the ones that work for your business and your customers. No two businesses are alike, so it’s imperative that you test and track which subject lines perform the best. 

If you’re stuck on how to write effective email subject lines, there are automated tools out that that can help. But beware – not all tools are as effective as they might seem. Our friends at Venngage wrote an interesting study on this that you should definitely check out.

When you do enough testing, you’ll start to develop your own set of best practices for your store’s email marketing.

What should you test? Start with the best practices we went over in this article:

  • Subject line length
  • Using a customer’s name
  • Type of discount (and how you phrase it)
  • Various types of social proof

The number of things you can test is nearly infinite. What matters is that you start testing. Rare makes it easy to run A/B tests, in which you create two different versions of an email and then randomly send them to half of your list. You can then compare which subject line performs better.

Of course, subject lines aren’t the only thing you can (or should) test and track, but they’re a great place to start. Just make sure that when running an A/B test, the only variation between your emails is the subject line, otherwise, you won’t be able to know if the subject line is what made the difference.

Once you’ve run a few A/B tests, you can review the results and tweak your future marketing messages. The results will likely surprise you. What sounds like the most compelling headline of the century will fall flat, while another one that seemed boring will drive huge numbers of sales.

Start Sending Better Emails Today

Writing effective subject lines is a critical component of email marketing best practices. Writing great emails is worthless, however, if you don’t have the correct tool to deliver them. This is where Rare comes in. We offer everything you need to send emails that make more sales. 

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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