The ultimate guide to email subject lines (plus best practices)

In a world where it's increasingly important to put our best foot forward as email marketers, maintaining focus on creating great and effective email subject lines should always be top of mind.

A subject line should be an email’s most thought-out and finely crafted sentence or phrase, because it’s the first thing your subscribers see.

It can sometimes be difficult to tell what the parameters of a successful subject line are. At the end of the day, once your campaigns are in motion, you'll need to find what works for your brand and your audience, specifically.

Here’s a deep dive into the best ways to write an effective subject line for your email campaigns.  

3 email subject line best practices

Search the internet and you'll find dozens—maybe even hundreds—of different opinions of what makes an irresistible email subject line.

Clashing viewpoints boil down to the fact that email marketing is an industry that thrives in the digital world, where nothing stays the same: not consumer behavior, not email platforms, and not online sales solutions.

Are you currently guided by the three practices below? We chose them precisely because they may seem self-contradictory—even though they work.

Use action, command and/or emotional words.

Here’s the key: use one or two, but not all. 

The general idea for all three is to evoke a strong and hopefully reflexive response. But if you attempt to use all of them in one thought, the message can get muddled. You can’t exactly mix a call-to-action type subject line with one that’s meant to rile people up.

Better: Will you put down your phone to save a child's life?

Worse: Stop looking at your phone and save a child's life

Open with a promise.

You should promise your readers something in the subject line without being able to follow through and deliver what they expect in the body of the email.

Part of knowing your email subject line best practices is recognizing what’s unsaid. Not doing this correctly can result in better open rates short term, but an increasing number of people hitting unsubscribe. 

Better: Lose weight while you sleep

Worse: Lose 40 pounds by the end of this month 

Ask questions, both closed and open-ended.

Email subject line best practices often note that questions should be open-ended, but that doesn’t consider what the text is saying.

If you pair a close-ended question with something your readers desperately want, they’re more likely to click through to your full email.

Better open-ended: Here’s 30% off. What’s your next order?

Better close-ended: Want 30% off on your next order?

Worse: How can you get a discount on your next order?

12 tried and tested email subject line best practices

There are some best practices that don’t change—or if they do, it's only by a little bit. 

Some suggestions apply to online writing in general. Most, if not all, require that you be guided by a keen knowledge of your audience. It’s not about keeping up with trends as much as it is understanding what will resonate with your subscribers.

Below are 12 email subject line best practices that we think will help make your best work even better. 

Write something short—but not too short.

With contrasting opinions on how many words is a “just right” length, you might feel like Goldilocks. What if we told you that you’re onto something?

There’s no universally decided correct amount of words—only best estimates—so the ideal is really what it takes for you to get straight to the point. Keep it interesting and accept that most people have a short attention span.

Better: Enjoy a complimentary couples spa package

Worse: Couples spa package

Start with more important information.

What you lead with is what readers tend to remember. This advice has also evolved to be one of the more modern email subject line best practices, because of smartphone screen displays.

What you lead with is what readers tend to remember. This advice has also evolved to be one of the more modern email subject line best practices, because of smartphone screen displays.

Source: Campaign Monitor

If your subscribers happen to check their email on their phones, even a medium length subject line may be cut off. That’s why you front-load the parts that need to be communicated, no matter what.

Better: Summer sale: Get 25% off sundresses 

Worse: Get these beautiful sundresses at 25% off during our summer sale

Focus on a benefit or a pain point.

Similar to using emotional words, focusing on what’s beneficial or painful can evoke strong reactions and encourage more clicks.

Better benefit-based: 5 ways to boost email open rates with better subject lines

Better pain point-based: 5 subject line mistakes (and how they hurt email open rates)

Worse: Email subject lines and open rates

Add a number in your subject line.

Do you know why listicles are popular? It’s because using numbers in titles and headlines can bring more than twice as much traffic to blog posts, especially if they’re placed at the start.

Do you know why listicles are popular? It’s because using numbers in titles and headlines can bring more than twice as much traffic to blog posts, especially if they’re placed at the start.

Source: Campaign Monitor

Numbers have a similar effect on subject lines. They not only catch a reader’s attention but can also convey credibility, augment a promise or provide specific information. 

Better: 11 ways to convert subscribers into customers

Worse: About your email subscribers and customers

When appropriate, use at least one emoji.

Emoji use is another one of those email subject line best practices that took form decades after email marketing was invented. 

Only use emojis if your brand identity is flexible enough to accommodate it. Even if this is the case, don’t go overboard and use multiple emojis in every single subject line.  

Make sure that your audience will receive an emoji the way you intend it, as well. For example: If you use a “sign of the horns” emoji 🤘 in an email subject line promoting a heavy metal concert in the US, it will probably help with conversions. But in Brazil, Italy, and several other countries, the same emoji suggests a cheating romantic partner. Yikes!  

Better: 🌊 Get 25% off your first bikini and catch a wave today 🌊

Worse: 🌊☀️Don’t you just ❤️ our new summer 👙👙👙 at 25% off? ☀️🌊

Create a sense of urgency.

Highlight limited stocks, sale and discount deadlines, or exclusive offers. 

The point is to make your email subscribers feel like they need to respond and take action or else risk being left out.

Better: BBQ Festival: 10 free tickets left!

Worse: We’re giving away tickets to the BBQ Festival

Get people curious enough to click.

Curiosity can be aroused in many ways. Some email subject line best practices above actually already do this. When you use open with a question or focus on a benefit or pain point, you are counting on your readers’ curiosity to get them to open your email. “How-to” subject lines may fall under this, too.

Curiosity can be aroused in many ways. Some email subject line best practices above actually already do this.

Source: Really Good Emails

Be careful about sacrificing conciseness for curiosity’s sake. You can try A/B testing to find out if your audience responds better to mystery or to a direct approach.

Better: The real reason no one replies to your tweets

Worse: Identifying your Twitter engagement problem

Be punny or funny—or both.

A joke or some snarky wordplay can break the rules and be a hit with your subscribers—or it can backfire. Funny subject lines are tricky to write and harder to execute than more email marketers realize.

Funny subject lines are tricky to write and harder to execute than more email marketers realize.

Source: Really Good Emails

Truth be told, we’re not entirely sure about the quality of our better/worse examples below.  Have we mentioned that this best practice necessitates a relatable sense of humor? 

Better: There are no deals in this email

Worse: Orange you glad you’re reading this on an Apple?

Try alliteration, consonance or rhyming.

These literary devices are popular in songwriting and creative literature—as well as email subject lines—because they break the monotony and add memorable elements. 

These literary devices are popular in songwriting and creative literature—as well as email subject lines—because they break the monotony and add memorable elements.

Source: Campaign Monitor

Just don’t go overboard! Remember that you’re writing email subject lines, and not beat poetry.

Better: 5 fall fashion don’ts for 2019    

Worse: 5 fall fashion faux pas for females

Don’t get too excited.

All caps and punctuation marks are fine in moderation. When you overdo either, you don’t convey excitement as much as your impart anxiety.

Better: Enjoy FREE delivery for purchases $100 and above today! 

Worse: $100 WORTH IN YOUR CART??? ENJOY FREE DELIVERY ON US!!!

Make a personal connection.

Personalizing email subject lines leads to better open rates, period. It’s also very easy to do at a basic level: Just include the subscriber’s name in the text.

Personalizing email subject lines leads to better open rates, period. It’s also very easy to do at a basic level: Just include the subscriber’s name in the text.

Source: Really Good Emails

Advancements in technology can aid in putting in more personal touches that draw from geographical location or buying behavior, as well. 

Better: “Thanks for participating in our Labor Day Sale, Maria!”

Worse: “Here’s the online receipt of your Labor Day Sale purchases” 

Avoid spam words as much as possible. 

Email spam filters are constantly evolving. The best you can do is avoid trigger words and phrases as much as you can, as you craft relevant subject lines for your email marketing campaigns.

A/B testing will help here as well if you are unsure whether one of your subject lines is unique enough to survive a spam filter.

Better: Book now to get 50% off weekend holiday accommodations

Worse: 50% off fantastic deal on weekend getaways for a limited time

Wrap up

Following email subject line best practices makes it easier for digital marketers to make a good impression on their email subscribers.

There are many different opinions on email subject lines best practices because best practices evolve over time. These adjustments are due to changing online consumer behaviors, as well as technological considerations. 

Most email subject line best practices that have stood the test of time are rooted in understanding your audience, as opposed to chasing trends or shortcuts to get higher open rates and conversions.

In this blog, we’ve compiled a total of 15 email subject line best practices to help you make your email campaigns better and more effective.

Need more concrete advice on how to write a great subject line? Check out more engagement tips and tricks from Emma.  

About the Author

Emma Email

Emma is an email marketing platform that gives you all the tools you need to send campaigns that really connect with your subscribers. Unlike other email providers, Emma puts their customers first. It's email marketing that works for you.

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