Email Marketing Mastery: 9 Tips and Tricks for Crafting Killer Subject Lines


People say – do not judge a book by its cover. But we do it all the time. Surprisingly, this fact has much in common with using subject lines in email marketing.

But let’s go back to books. Why do we judge covers? Well, it’s just a quick way to determine if the book fits your taste. Take the example of “Eragon.” All fantasy enthusiasts would consider reading it thanks to the dragon image on the cover!

Similarly, “Atomic Habits”; its minimalistic design immediately focuses attention on the title, attracting all readers who would like to work on this issue. 

We judge books by covers because covers are promises about what we’ll find inside. So, we choose only those promises that sound compelling.

The same is true for email marketing; people only open emails whose subject lines attract them and make them curious about the content inside. That means subject lines ensure that your email will be opened, making it a crucial element of your email marketing strategy.

I hope you agree at this point that it’s pretty impossible to become an email marketing master without killer subject lines. So, let me introduce you to your roadmap to success. 

In this article, you’ll find answers to the following questions:

  • What is an email subject line?
  • Why are good email subject lines important?
  • What makes a good email subject line?
  • What are the best subject lines tricks, and why do they work?
  • What are examples of killer subject lines?

In short, this guide covers the essentials for crafting subject lines that will ensure excellent email open rates. So, without further ado, let’s explore!

What is an email subject line?

It’s a basic question we can answer in at least three ways.

  • Visually, an email subject line is a text that appears at the top of an email message.
  • From a sender’s point of view, an email subject line is a brief summary of the email’s contents.
  • From the viewpoint of email recipients, an email subject line is a hint and promise about what’s inside.

But what is an email subject line for marketing specialists? In this case, it’s a way to catch a receiver’s attention.

Creating good email subject lines: why it matters?

As I mentioned before, subject lines serve as book covers. They help email recipients decide whether email content will be worth their time. It’s not solely my opinion!

Here are some rock-solid statistics proving it:

  • 47% of email recipients open emails based on the subject lines alone (Tidio, 2022).
  • A similar survey reports that 64% decide to open emails based on subject lines. (Barilliance, 2021)
  • 69% of email recipients report emails as spam based on the subject line alone. (Invesp, 2021)
  • 33% open emails because of catchy subject lines. (OptinMonster, 2020)

The data I presented leaves no room for doubt: exceptional email subject lines can make a massive difference in your marketing email campaigns.

The anatomy of a winning subject line: uncovering the essentials.

In math, you learn addition before you learn calculus.

When doing workouts, you learn how to keep a proper posture before lifting weights.

Playing piano, you practice scales and arpeggios before switching complex songs.

Here’s the thing: tricks are secret knowledge for people who know fundamentals. So, here, we’ll build this common ground. Let’s uncover the essential elements that every subject line should include.


I have to confess: this was where my first subject lines failed.

There were my early days in a new job role. With a head full of advice, inspiration, and power words, I focused on creating intriguing and exciting subject lines. You can guess how long they were.

Later on, I came across research explaining that issue. The thing is that, according to different sources, 46% or even 77% of email openings take place on mobile. So, the number of featured words is limited.

Additionally, this short strategy ensures that people scanning their mailbox will read the entire message.

The sweet spot? Your subject lines should be shorter than 50 characters. In the ReturnPath study, maintaining this length resulted in 12% higher email newsletter open rates and 75% higher click-through rates than other emails.

In my case, it helped me be clearer and more direct with my subject line intention. Also, short ones sound much more appealing!


“How to Get Discovered as a Writer” was a title of an email I received recently from Copyblogger.

I was interested in this email because I’m a writer, I’m aware of how competitive this niche is, and it was close to a new year, a time of making life changes. In short, I knew that inside is something relevant to me.

Here. Stop. Relevancy is the key.

Your email subject lines should be relevant to recipients – and here are 3 ways to achieve it:

  • Poke at pain points. Take the example of Duolingo and its Learn a language with only 5 minutes per day. Such an accurate title! It informs all busy people who complain about lack of time that there is a solution fitting their needs. Follow this approach: segment your subscribers and identify their pain points. Then, address them in your subject lines. Nothing is more relevant than offering solutions to problems.
  • Make it time-sensitive. What matters the most? The thing that matters now. In winter, I’m more interested in hot chocolate than during summer, and on Monday, I’m more interested in coffee than on a lazy Sunday morning. Take it into account when writing subject lines and highlight urgent topics.
  • Be trendy. Trends are my favorite strategy because they connect people from different segments. Your audience may vary about their pain points, but at the same time, they all can be “Wednesday” fans. Benefit from it! Yes, influencer marketing also works for subject lines.

Using one of those 3 ideas, you can ensure that your subject line is relevant to a reader.

Non-spam words

Your email may land in spam without being opened. 

As mentioned above, 7 out of 10 people report email as spam based on the subject line alone. As a result, it can cause spam filters to flag your address and lower the email sender’s reputation score for the entire email domain.

Stay away from the SPAM folder by avoiding those spam trigger words:

FinancialUrgencyHealth & medicineLegal
advertisinglimited time offerlose weightlegal notice
increase salesget it nowweight lossin accordance with laws
increase trafficact nowdietreserves the right
web trafficurgentonline pharmacysubject to
internet marketingonce in a lifetimeinsuranceterms and conditions
email marketinglimited suppliesmedicine
click herecall nowdrugs
free trialorder today
multi-level marketinglast chance
guaranteehurry up
warrantytoday only
order nowexpires today
sign up
generate leads

Besides, steer clear of $$$, excess exclamation points and CAPITALS.

It should keep your emails safe and well-delivered.


As humans, we have a natural desire to explore. The same is true about your potential customers. They would love to open your email; at least as long as you promise something exciting inside.

So, one of the four essentials of a successful email subject line is: to evoke curiosity. You won’t be disappointed with opening rates as long as you’ll come with catchy topics.

But at this point, do not sacrifice the next matter…

Keeping the promise

Never-ever disappoint your email clients. Whether you proclaim to them the new idea to save time spent on household chores or a new way to relax in 5 minutes: deliver on your promise.

In other words, make your subject line related to your email body. Otherwise, it may be the last time your potential customers open your email.

9 Tips & Tricks for Crafting Effective Email Subject Line (with examples)

Finally, we reached THIS section. Awaited as the organic traffic growth, anticipated as marketing campaign results.

Here, we’ll discuss tips and tricks to help you craft winning subject lines. So, get inspired!

The ‘FOMO’ Effect

You could hear about the FOMO: fear of missing out. It’s a feeling of scarcity people get when they may miss the chance, whatever the matter. Limited offer? The last chance to get the sale? A unique product for one day only? All work the same.

The strategy is to create a sense of urgency, so the email recipient would like to act immediately and open your message.

Some examples:

  • Our winter sale ends 9th January –IKEA
  • Your discounts expire soon. –Poshmark
  • Shirts for $39 ends at midnight –Charles Tyrwhitt
  • Grab a ride pass before they’re gone –Uber
  • Barnstable is in high demand for August –Airbnb
  • Never again sale –InstantBoss Club

The Curiosity Gap

What is the curiosity gap? It’s a crack between what you know and what you want to know. As humans, we have an innate need to fill this gap.

Let me show an example.

Work & Travel – Disaster or Remedy? [2022 study + infographics]

We use this subject line to promote the Passport-Photo.Online study about workation. How does it play with the curiosity gap?

  1. It informs you that mixing work and travel can be beneficial or dangerous.
  2. It doesn’t give you the answer, forcing you to check it in the email.

I don’t advise creating vague subject lines. Just remember: do not tell all your secrets ahead of time.

Some other examples:

  • Is this the hottest career in marketing? – Digital Marketer
  • 9 Disgusting Facts about Thanksgiving – Eat This Not That
  • Products the celebs are wearing – Sephora
  • Wanted: Cute and affordable fashions – Guess


The person’s name is to that person the sweetest sound.

One of the most successful strategies to pick recipients’ attention is to call their names in the subject line.

But if you want to stay out of the crowd, use other ways to personalize your email “headline.” 

Segment email recipients using their locations, hobbies, or commonly used portals. Find the name or topic they are familiar with and use it to build the impression of trustworthiness.


  • Happy Birthday Mary – Surprise Inside! – Rent the Runway
  • Mary, check out these hand-picked looks – Guess
  • For the list of people who’ve attended a webinar in the past, you could write, “Enjoyed my last webinar? Check this one out!”

Numbers & Statistics

Humans link numbers with data. With solid, proven statements. Reliable and fresh insights. With a value.

The Kelntly latest research shows that email subject lines using numbers generate a 20% open rate versus 12% without numbers. That’s a huge difference. The Nielsen Norman Group explains that it works because numbers catch the digital readers’ eyes.


  • How 35 influencers grew their sites from 0-10K visitors – AppSumo
  • Take $20 off your order of $25 or more – UberEats
  • 1,750 points for you. Valentine’s flowers & more for them. – JetBlue
  • Try To Avoid These 27 People On New Year’s Eve – Thrillist
  • A Native Ad in 60 Minutes or Less – Digital Marketer

Did you notice it? In the last example, they could simply write “an hour”; instead, they decide to include the number to catch the reader’s attention.


If animals could talk, which would be the smartest?

You tried to answer it in your mind, didn’t you? Questions immediately involve readers by starting an inner dialogue. A question is asked, and you can’t help yourself responding.

Try to increase your email recipients’ engagement by using questions. Here is how experts do it:

  • Hologram Shorts?! – Chubbies
  • Is this the hottest career in marketing? – Digital Marketer
  • How Have You Progressed Since the Third Grade? – Jeremy Gitomer
  • You don’t want FOMO do you? – AppSumo

(Returning to the opening question, I bet on a red panda!)


Data, strategies, methods… Aren’t we too mature for marketing?

Do not be so serious, and let’s make people smile! You can do it using onomatopoeia: a word that phonetically imitates or resembles the sound it describes. It results in funny and eye-catching effects!


  • Psst… Coming Soon… Shh, for your eyes only — Monica Vinader
  • Uh-oh, your prescription is expiring – Warby Parker
  • Boom shakalak! Let’s get started. -TicTail
  • Whoops — we hadn’t had our coffee this morning – Catchafire

Take time to rhyme

It’s another strategy to evoke the inner child.

Do you remember nursery rhymes? Excellent, because it’s time to rhyme!

The power of this strategy is… the surprise. No one expects the piece of a poem in a mailbox!


  • Always our crush: blush – Morphe
  • 4 items to buy before you fly
  • These new decor styles bring smiles

Power words





What do those words have in common? Right, they are all power words!

Power words are words that trigger strong emotions in the reader. It’s all about how our brains work; those words trigger psychological and physiological responses, leading to high engagement or motivation to act.

Exaggerating: as you evoke emotions, your email recipients feel they can’t help opening your email.

Try it by yourself and explore the complete list of power words.

The list of inspirations:

  • Forget Your Troubles, Come On Get Matchy! – Patpat
  • Tonight only: A denim lover’s dream – Guess
  • 10 bizarre money habits making Millennials richer – Refinery29
  • These stunners are selling out fast – Sorel
  • Why’s everyone obsessed with retinol? – Estée Lauder Online

Action verbs

Actually, the subject line is similar to the CTA button. Its life purpose is to convince you to click.

The last subject line trick is to get inspired by CTAs language and experiment with action-oriented verbs!

Think about your subject line as an explicit instruction that should guide your email recipient. What would you like them to do? Click? Check out? Try?

Stir it up a bit. Id’ suggest: Discover, Explore, or Improve.

Explore action verbs and try to find the most exciting ones. This strategy will bring your subject lines to the next level. Here you have some master examples:

  • Rock the color of the year – Etsy
  • Steal these email templates… – Digital Marketer
  • Meet your new jeans – Topshop
  • Feed your guests without breaking the bank – Pizza Hut
  • Get more kitchen space with these easy fixes – IKEA
  • Stop wasting money on ink – HP

Final thoughts

Glad to see you at the end of this piece! I hope you enjoyed this journey and found my insights inspiring.

Let me crown you the Subject Line Email Marketing Master! Remember, As with any craft, writing subject lines takes practice, collecting data and analyzing them. But with this guide, you’re on the right track.

Good luck – and do not hesitate to send me your winning subject lines.

About the author

Karolina Turowska

Karolina Turowska, a writer and travel enthusiast at <a href="">PhotoAiD</span></a>. When she writes, she loves bringing dry facts to life. When it comes to traveling, she loves bikes.

By Karolina Turowska