Email Subject Line Copywriting: Secrets to Boost Email Open Rates

Zamira Vecsei

• 8 min read

Another email, another boring and dull subject line.

Version A — unread. Version B — unread. Version C — unread. Honestly, the process of crafting subject lines is easy. The mechanical, uninteresting subject line. It's easy. All you have to do is copy and paste.

But if you want to craft catchy email subject lines — ones that get your potential customer to stop their work and quickly jump on to open your email — this article is for you.

Let’s dive into how you can boost email open rates by mastering email subject line copywriting.

Why are subject lines important?

Email subject lines are pivotal in determining the success of your email campaigns.

Here's a glimpse into some compelling statistics highlighting their importance:

  • Nearly half of ‌email recipients decide whether to open emails based solely on the subject line.
  • 69% of email users will mark the email as spam after reading the subject line.
  • Including personalized elements in the subject line increases the open rate by 26%.
  • Email subject lines that include exactly 6–10 words have the highest open rate (21%)
  • Emails that have a question mark in the subject lines can boost open rates by as much as 44%.

These statistics clearly illustrate the crucial role of subject lines in email marketing and the need to dial in your email subject line copywriting for best results.

Tips to craft a catchy email subject line

While it's important to know the different tactics to craft an irresistible subject line, know that the process of crafting these subject lines isn't quick. It takes time.

Here are a few tips that can help you increase your efficiency and craft an awesome email subject line.

  • Keep it short
  • Add social proof
  • Offer value
  • Add emojis
  • Keep it brand-consistent

In other words, the small details matter. Nail these things, and you’re off to the races.

From there, you can use these bonus tips to take your email subject line copywriting to the next level.

Bonus Tip #1: A/B test your subject lines

The best way to find out which subject lines perform best for your email campaign is through A/B testing.

With A/B testing, you experiment with different subject lines. Subject lines that receive maximum engagement from a segmented group of recipients are the ones you should send to your entire email list.

To A/B test your subject lines:

  • Create two versions of your subject line
  • Randomly divide your subject line into two groups
  • Send each group a different subject line
  • Measure the open rates for both subject lines
  • Use the winning subject line for your entire email marketing campaign
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Pro tip: Leverage the expertise of a full-service email marketing agency that specializes in high-converting emails to measure the effectiveness of your email subject lines.

Bonus Tip #2: Use AI to craft perfect email subject lines

Sometimes, our creative juices run on empty, and we hit the dreaded writer's block.

Don't let that hold you back from writing stellar email subjects. That's where the power of artificial intelligence saves the day.

For instance, with an AI writer, you can write instant marketing copy for your subject lines and email content. All you have to do is give the AI writer the prompt on the topic, and it'll generate the subject line for you.

While this sounds idyllic, it's crucial to ensure a human touch in every piece of content created. This approach ensures that your messages resonate deeply with your audience, maintaining a personal connection that feels genuine and heartfelt.

5 examples of catchy subject lines

If you don't get the subject line right — your potential customer won't open the email.

You don't want that, right? But here's the thing: crafting compelling subject lines is tricky. The goal is to encourage your audience to open your emails after reading the subject line.

So, without further ado, here are a few ways to craft irresistible subject line examples and tactics to boost your email open rates.

Tactic #1: Personalize your subject lines

When you personalize subject lines, it resonates with the recipient as it builds a personal connection with them.

That's why subject lines with the recipient's name are opened 18.30% more than non-personalized subject lines, which have an open rate of 15.70%.

There are multiple ways you can add personalization to subject lines. Some of these personalization elements include:

However, personalizing the subject line based on the recipient's first name is one of the common personalization practices.

For example, Sugar Cosmetics, a beauty brand, personalized its subject line with the recipient's first name.

Subject line: Nidhi, sit tight, for the biggest reveal🔥

Preview text: Here's the biggest announcement

A personalized subject line with the recipient’s first name

Screenshot by Nidhi Kala

Why do we like this subject line?

  • The subject line includes the recipient's first name and builds curiosity.
  • The subject line includes an emoji, which is great because subject lines with emojis have a 56% higher open rate.

Tactic #2: Spark curiosity with your subject line

Creating a subject line that generates curiosity in people is a great way to drop a teaser of the valuable information that you are providing to the recipient.

Here are some examples of email subject lines that spark curiosity:

  • THE NIGHTMARE IS OVER
  • Wait, WHAT?
  • Not A Joke!
  • This is a game-changer.
  • This is ridiculous
  • Don't open this email.
  • You won't believe what's inside

Take a look at this subject line by Flipkart, an e-commerce store.

Subject line: Canceled: All Plans for Today ❌

Preview text: This is the most important thing

Subject line by Flipkart that triggers curiosity

Screenshot by Nidhi Kala

Why do we like this subject line?

When the recipient reads this subject line for the first time, it makes them curious and piques their interest into thinking about which plans have been canceled.

The subject line creates a sense of intrigue in the recipient's mind and leaves a gap of knowledge, which the recipient can find only by clicking on the email.

Tactic #3: Create a sense of urgency

Your email recipient will likely open the email if it is a limited-period deal. The reason is simple: it instigates fear of missing out (FOMO) in the target audience, which encourages them to take action.

This strategy works well for sales emails (read: promotional emails) —  for discounts and flash sales.

Here are some examples of how you can use some catchy and powerful words to instigate FOMO in your emails:

  • Unlock EXCLUSIVE content
  • Limited time period
  • Closing Soon!
  • WARNING... Few days left
  • 70% off sale ends at Midnight
  • Grab a ride pass before they're gone.  — UBER

Here's a sneak peek at how Grammarly creates a sense of urgency with their limited-time discount on the Grammarly premium subscription.

Subject line: Final Day to Save 45% Off Premium

Preview text: Organize your ideas and seize your next opportunity

Subject line by Grammarly creating a sense of urgency

Screenshot by Nidhi Kala

Why does this subject line?

The subject line highlights the exact discount Grammarly is offering to its subscribers.

Also, it's time-based urgency with words like "final day” and power words like "save” to accentuate the FOMO.

Tactic #4: Include numbers in your subject line

Did you know that adding numbers in your blog titles can increase your click-through rate by 36%? The same concept works for subject lines.

When the recipient sees a number in a subject line, it creates a visualization of order in their minds. This encourages them to read the email because they have the end goal in mind.

For example, a subject line might say, "5 Tips to Amplify Your Productivity" or, "This is How I Improved my Productivity by 70%."

Take a look at this example by Clean Origin, a brand specializing in engagement rings.

Subject line: 3 carats is the new 1 ct

Preview text: A bigger diamond for less

Numbers included in the subject line by Clean Origin

Screenshot by Nidhi Kala

Why do we like this subject line?

This subject line included numbers twice in the headline: 3 and 1. This draws the reader's attention and creates a visual view in their minds of the product, i.e., engagement rings.

Just by reading the subject line and the preview text, the target audience knows what the body of the email is about — a 3 ct diamond ring.

Here's another example by Campus, a community college that's included numbers in their subject line.

Subject line: A 10-Minute Investment for a Lifetime of Success: Complete Your Campus Application

Email subject line by Campus includes numbers and time-based triggers

Screenshot by Nidhi Kala

Why does this subject line work?

The subject line includes the phrase '10-Minute Investment', which instantly helps the recipient visualize the amount of time it'll take for them to fill out the application.

Tactic #5: Add the element of storytelling in the subject line

Studies show that storytelling increases oxytocin and positive emotions and decreases cortisol and pain in hospitalized children.

Storytelling builds an emotional connection among people. That's why it's a great tactic to use in your email subject lines, as StudioSuits does to promote its impeccable custom suits and pants.

Subject line: Dress like a Peak Blinder: Classic Style Awaits

Email subject line that uses the elements of storytelling

Screenshot by Nidhi Kala

Why do we like this subject line?

By adding similes (Dresses like Peak Blinder), the brand creates an emotional connection with its audience, especially with those inspired by Peak Blinder's fashion style.

Tactic #6: Avoid using spammy words

As we mentioned earlier, 69% of email recipients will mark emails as spam after reading the subject line preview in their inbox.

While ‌recipients do open emails with spammy subject lines, they usually end up landing in the spam folder. The result? A reduction in the overall email deliverability score. Surely, you don't want that in your email outreach campaigns.

And that's why it's crucial to make sure not to use spammy words in your subject lines. Some of the spammy words that brands use in their subject lines include:

  • Free
  • Act now
  • Guarantee

For example, Shope Lune, a jewelry brand, sends a spammy subject line to its email subscribers.

Subject line: Free Rainbow Lune Tag Necklace

Preview text: Free Rainbow Lune Tag necklaces on orders above 5,000

Subject line using spammy words

Screenshot by Nidhi Kala

Why does this subject line not work?

The subject line and preview text contain words like "free" that trigger spam. Because of this, ‌emails are likely to land in the spam folder, especially when the brand has a lower email deliverability score.

Wrapping Up

Creating an irresistible subject line that grabs your recipient's attention requires creativity and experimentation. The tactics we shared today will help you write some interesting subject lines that you can use in your next email campaign.

Remember, there's no hard-and-fast rule to email subject line copywriting. Always A/B test your headlines and find what works best for you.

You’ve mastered the subject line. Now let's create an email that's just as captivating.

Try Chamaileon, a drag-and-drop email builder that's as seamless (if not more so) as those flashy design tools, to craft your stunning email today!