The Key to Email Subject Lines That Get Opened: 8 Data-Backed Ways To Boost Open Rates

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Here’s the thing: You want to write email subject lines that actually work. You already know that subject lines get noticed in busy inboxes (because you compete against 121 emails an average office worker receives every single day). And you know the only way to get traffic and conversions—and ultimately sales—is to stand out.

In short: Between many other skills, you need to know what makes a great subject line work to be successful as an email marketer.

The email subject line tips in this article are backed by 20 studies and CoSchedule’s very own data from our Campaign Monitor account.

The goal here is to help you learn and remember the mechanics the best-performing email subject lines often share.

But before we get into that, let’s give you a great starting point.

Start with these 20 creative email subject line example templates

Sometimes, that blinking cursor can be intimidating.

So, use the following email subject line templates as a type of “swipe file”. Copy, paste, then fill in the blanks to get started.

  1. Stop {Undesirable Emotion} Now
  2. {Desirable Outcome} (Your First 3 Steps)
  3. New {Thing}: What It Means For {Audience’s Role}
  4. What {Credible Influencers} Are Saying About {Topic}
  5. {Someone Audience Looks Up To} Can Afford Any {Product}, She Uses…
  6. Best {Emoji} + {Emoji} + {Emoji} = {Emoji}
  7. {Topic}, {Topic}, and {Seemingly Unrelated Topic}?
  8. {Personalized Company Name} + 497% More {Need} = {Emoji}
  9. {Emoji} Your {Emoji} With…
  10. {Personalized Name}, Earn {Something Desirable} Today Only
  11. You’re Missing Out On {Something Desirable}
  12. Tonight Only: A {Audience’s Role}’s Dream
  13. Want 587% More {Something Desirable}? {Emoji}
  14. This Is A Sales Email {Emoji}
  15. Don’t Forget! {Event} Today {Emoji}
  16. …When You’re Sick And Tired Of {Something Undesirable} {Emoji}
  17. “{Quote}”
  18. A {Topic} Process To Reduce 30-50% Workload {Emoji}
  19. {Topic} + {Topic} + {Topic}
  20. “I Love {Something Undesirable}!” (said no one ever)

Then, use the following 7 tips to optimize your subject line.

1. Leverage words that have been proven to boost email open rates.

My research into email subject line mechanics dug up 100 words, terms, and symbols that are highly like to influence open rates when you use them in your subject lines:

Further analysis suggests you’ll get the best open rates by using 3 or more of the words/terms and/or symbols from that list in your subject line.

2. Remove words that reduce open rates (or trigger spam filters)

Just as there are words that typically increase email open rates when you use them in subject lines, there are words that negate those opens, too.

Here’s a shortlist of 100 words, terms, and symbols to avoid using in your email subject lines:

It’s best practice to use zero of these words, terms, or symbols in your subject lines.

3. Include a number in your subject line

Including numbers in blog post headlines increases clickthrough rates by 206%.

Even though the research refers specifically to blog posts, subject lines in emails serve a very similar purpose: Increase clicks from a list (blog post category pages, social news feeds, email inboxes, etc.).

It turns out, like blog post headlines, using numbers in your subject lines increases email open rates.

A recent study that analyzed 115 million emails suggests email open and reply rates are higher when a number is present in the subject line. Numbers and data get your emails noticed, demonstrate a clear and straightforward message about your offer, and set the right expectations for your readers, helping draw them in.

Include at least one number in your subject line to boost your email open rates.

4. Put an emoji in your subject line ?

Campaign Monitor recently researched the use of emojis in subject lines to understand if their inclusion increased open rates. When I chatted with Kim Courvoisier a few months ago, who was a marketer here at Campaign Monitor, she suggested:

Brands that are using emojis have seen a 56% increase in their unique open rates. This isn’t a report from experience. We’re really seeing an increase in emojis, and you can use them as a brand appropriately, and they do add a nice little bit of flare and attention-getting in the inbox.

If you’re wondering where you can find emojis:

  • Windows: Use the WIN + . (actual period punctuation mark) to open the emoji keyboard.
  • Mac: Hit Control + Command + Spacebar to open the emoji window.

If neither of these suggestions works: Check out GetEmoji and copy/paste.

Best practice suggests using 1-4 emojis in your subject line will boost your email open rates.

5. Keep your email subject lines the right character length

While the 20 studies analyzed for this article differed drastically on the topic of email subject line length, everyone agrees: Keep your subject lines short.

50% of all emails are opened on mobile devices. iPhones show about 35-38 characters in portrait mode, and Galaxy phones show roughly 33 characters in portrait mode.

Long story short: Make sure the 50% of your subscribers who will open your email on their mobile device can actually read the entire subject line.

Best practice suggests subject lines that are 17-24 characters long are most likely to boost your email open rates.

6. Keep your email subject lines the right word length

The studies suggest the more words you use in your subject line, the fewer opens you’ll get.

That means your best best is to use a short number of characters as well as a short number of words.

Use 3-5 words in your subject line to boost your email open rates.

Research suggests that subject lines in title case are most effective at boosting your open and reply rates.

That study suggests the psychological reasoning behind title case’s success is perceived authority. Even something as small as using title case instead of sentence case or all lower case in an email subject line is an authority badge for the sender.

It’s like showing up to an interview in a suit instead of a pair of shorts.

What does title case actually look like?

  • Title case: Pack My Box With Five Dozen Liquor Jugs
  • Sentence case: Pack my box with five dozen liquor jugs
  • Lower case: pack my box with five dozen liquor jugs

Write your subject lines in title case to boost your email open rates.

Bonus tip: Utilize preheader text to boost subject line open rates

Preheaders are excellent to use after your subject lines. Preheaders, also known as the “Johnson box,” summarize the content in your email for added enticement. Your audience gets a chance to preview the email, even while it sits unopened in their inbox.

This is a great way to hook your reader, compelling them to open their emails. Also, adding emails with preheaders and subject lines can boost open rates by 7%, so add this practice to your email marketing repertoire to see greater opens and better return from your emails.

Whether your customers open their emails on mobile devices or desktop computers, preheaders add more space for you to hook your readers and impress them.

How to write an email preheader

Want to know the basics to write an effective email preheader? Here are three tips to get you started.

Limit the character count

An ideal preheader includes 85-100 characters. You want to keep it short and straight to the point. Your audience will only spend a few seconds scanning an email, so condensing your preheader, with a hook included, will keep them from skipping your email entirely.

Make it meaningful

Since you only have up to 100 characters, you need to include engaging and meaningful language in your preheader.

Use strong verbs and keywords and introduce the subject of your email immediately. You can even include emojis to grab your customer’s attention if your branding allows it.

Add personalization where you can

It’s always a good idea to personalize all elements of your email and the preheader is no different.

Include your customer immediately, whether that means using their name as the first word or providing them with pertinent information. People love to see their name on an emails=, and they especially love updates pertaining to products they ordered online.

How to combine a subject line and preheader for a compelling email

So, now you have the secret formula for crafting an attractive subject line and preheader. However, what do a great subject line and preheader look like? How do you craft a preheader and subject line that boosts open rates?

Here are four examples from companies who got their subject line strategy right.


This subject line is 5 words, hitting the target of 3-5 words for higher open rates.

In the preheader, Birchbox used the customer’s name as the very first word in the sentence. They also stuck a short, 7-word sentence at the very beginning of their preheader. This is a great idea to implement because the customer sees the premise of the email without opening it.

Source: Campaign Monitor


Skillshare gets down to the crux of their email–wasting no time. In the subject line, the company indicates how much time their customer has to act upon their subscription. Then, the preheader gets right down to the price.

Knowing basic information from the start gets customers to click fast. They know what they can expect by and clicking on this email, which means they’re more likely to actually purchase if they open it.




If there is one thing Netflix excels at besides entertainment, it’s short, punchy subject lines. In addition, this email is very simple in character and conversational in nature.



Netflix beckons their customer back with a 3-word call to action, “Come back today,” as if an old friend says they miss them. In the preheader is another call to action, this time appealing to an emotional need the customer might feel to enjoy themselves through the streaming service. This is a perfect example of a great subject line strategy that “hooks” your customer’s attention.

Wrap up

You want sales. But without email opens, you get zero clicks to your website which means zero traffic that you can convert which means zero sales.

Something as simple as email open rate can help you concentrate on the lead indicators that influence more significant metrics down the funnel.

So, if you’re thinking of improving your open rates with a little help from data:

  1. Use a few of the words that are proven to increase open rates.
  2. Avoid the terms that typically decrease open rates.
  3. Test using a number in your subject line.
  4. Include at least one emoji.
  5. Make it about 17-24 characters long.
  6. Shoot for approximately 3-5 words.
  7. Write it in title case.
  8. Utilize preheader text.
  9. Learn from other companies.
  10. You’ve got this.

Now that you understand why subject line open rates are so important, try your hand at creating your own with these formulas.


This article was originally published on Campaign Monitor.