How to Write Effective Subject Lines for Email Marketing

Last Updated on

January 27, 2023

Want to write email subject likes that work? Knowing how to write subject lines is crucial to any email marketing campaign. In this guide, we'll share how to write effective subject lines for email marketing in 2019 (with examples that get the best open rates).

I think you’ll agree with me when I say:

Subject lines can make or break the success of your email marketing.

If an email doesn’t get opened, nothing else can happen. Subscribers won’t read your message, won’t take action, and won’t convert!

That’s a lot of pressure.

However, after writing more than 1,000 emails, I can now say that writing subject lines is the most fun I have with my emails.

By the end of this blog post, I’m willing to bet that you’ll be having at leastas much fun with them as I do.

Plus, you’ll learn how to come up with effective subject lines that stand out in your subscribers’ inboxes and get your messages opened. In other words, you’ll know how to write subject lines that work.

Why Are Subject Lines So Important?

So you may be wondering why email subject lines are so important. Well, let me explain it from my point of view.

You see, I’m a recovering sales funnel fanatic. I see everything as a funnel. Including a single email.

Here’s what I mean. After someone opts in to your email list, every marketing email you send them is a miniature funnel, consisting of 6 parts…

  1. Sender name
  2. Subject line
  3. Preview text
  4. Opening sentence
  5. Body text
  6. Call to action(s)

The role of each of these 6 components is to move the reader further down the funnel and complete the next step.

Yes, the overall goal of the email is for the reader to take the desired action, which in most cases, is clicking on some link (and getting into another funnel – a landing page or a blog post).

But it doesn’t mean you should start talking about that action in the subject line.

The sole purpose of the email subject line is to persuade the recipient to open the email and read the first line.

At that point, it is the job of your opening sentence to keep their interest, and persuade them to read further.

So bottom line: don’t try to pack everything you can in your subject line. It’s not the time to sell. It might not even be the time to talk about the main point of your email. It’s just there to get them to open the email.

5 Strategies for Writing Subject Lines that Get Opened

Ready to learn how to write email subject lines that get opened?

Great! Let’s dive in…

1. Evoke Curiosity

Curiosity is something that we, as humans, simply can’t resist.

How many times have you seen a headline and thought it was probably clickbait, but you still had to click and check?

Your subject lines don’t have to (and shouldn’t) be spammy or clickbaity, though. You can evoke strong curiosity and still make it relevant to the topic of your email.

There is an art and a science to that. I’ll explain the science, and the art will come from practicing it over and over again.

After you’ve written your email, skim over it, looking for threads that can open themselves to fun references, unusual associations, controversies, or statements with double meaning.

If you’ve caught a thought or a statement like that, play with it and develop it into a short subject line that is asking to be opened.

Here is a curiosity subject line example from my own emails:

Subject line: GDPR WTF
Open rate: 35.8%

The email featured a breakdown of the recent GDPR regulations. I think GDPR is one of the most unfortunate abbreviations (it just screams at you “BORING”), so adding one more abbreviation to it felt funny (although, I admit it, risky).

I received at least a dozen replies to that email saying they enjoyed the subject line. #success

Here are a few more examples of curiosity-driven subject lines I pulled from my inbox:

Ramit Sethi:

  • I’m so good with Asian Moms
  • I LOL’d at this $300,000 comment

I think Ramit is just a god of email marketing in general, and he’s great with subject lines, too.

The first subject line above is just too good to miss out on (great example of both an unusual association and double meaning). The second one has a number (see the Do’s and Dont’s of subject lines below), and hints at a controversy (who would laugh at anything that’s $300,000?).

Charlie Hoehn:

  • are you kidding?
  • Why I quit my dream job working for Tim Ferriss

The first subject line is rich with associations: we can all remember ourselves in a situation where we could do no more than exclaim “are you kidding?” This subject line evokes strong emotions, so it works really well.

The second subject line evokes curiosity in a very literal sense: who would quit a job working with Tim Ferriss, especially if it’s a dream job?

2. Highlight the Big Benefit

Not all of your subject lines have to be mysterious: leading with the benefit also works really well.

First, understand what’s the main benefit of your email in one or two words. What does the reader get out of the email?

From there, you have a couple of options. You can be very straightforward and just use the main benefit as the subject line. It performs slightly worse than the next option I’ll talk about, but still gets decent results.


  • How to Email Important People (The Ebook)
  • 2015: Be The Exception
  • Can you build your business without spending a penny on ads?
  • The bravest people I know
  • Why creating a “newsletter” is a mistake

(Notice that while these subject lines are more straightforward, they are still using an element of curiosity to a smaller degree).

A more effective strategy is to combine your benefit with something unusual or (pardon the repetition) things that evoke curiosity.

Here’s a benefit subject line example from my email list:

Subject Line: Michael Scott + drip mistakes
Open rate: 30.4%

This email was about drip campaign mistakes to avoid, and it featured a funny GIF with Michael Scott from a popular TV show The Office.

Everyone loves The Office and Michael Scott (well, at least way more people love The Office than love drip campaigns). It’s somewhat relevant to the email, so I used it.

Other examples of benefit + curiosity email subject lines:

  • The truth about my first $1000 month (it almost killed me)
  • Replay coming down and other sad news
  • Why I started a conference
  • How I went from total nobody to “expert”, overnight

3. Write the Subject Line Last

I always start with writing out the whole email, editing and perfecting it, and only then thinking about the subject line.

It’s much easier to think of a punchy, rich subject line when you already have so much content to work with. The email you just wrote is a source of dozens of subject line ideas, and by trying to come up with the subject line first, you’re reaping yourself off that benefit.

So right after you write your email, skim through it and look for bits that you can feature in your subject line. Follow the advice from the other sections in this blog post when looking for subject line material (curiosity, benefit, number, etc.).

4. Use Numbers

In most cases, using a number (as a digit figure, e.g. 23) in your subject line will increase the open rate of your email.

It works for two reasons:

  1. Numbers add concreteness to (oftentimes) vague statements in subject lines
  2. Digits stand out among text

As with anything, don’t overuse it: if you use it in every email you send to your list, it will lose its effectiveness.

A company called Yesware analyzed millions of cold emails (which are different than marketing emails, but nevertheless they are emails), and found that subject lines with a number get an open rate 53.2% as compared to the 2015 average of 51.9%.

5. Only Use “Forbidden” Techniques Once in a While

There are some email marketing techniques I call “forbidden” — they are guaranteed to work, but essentially, you’re cheating.

It’s like killing a child in a movie as the director. You KNOW people will respond emotionally to that, so for a director of a drama film, it’s an easy way out.

When it comes to subject lines, an equivalent of that would be hinting at some dramatic change or using a clickbait.

For examples, in this blog post, Susan Su describes how she was able to reactivate a dormant email list with an email that had a 66% open rate within 24 hours of sending.

Subject line: Changes

Such a subject line, combined with the company brand, is very intriguing. If you see a subject line like “Changes” in your inbox on a Thursday afternoon at 4PM, you might be thinking…

HUH?! Am I getting fired? Is this company going out of business? What the heck is changing?

As Susan mentions, it creates a “curiosity gap” that makes opening the email an irresistible conclusion: you must find out what is changing.

Another example from my own emails:

Subject line: honey
Open rate: 44.8%

I sent that email after a long 3-month break from communication with my email list. My subscribers know my voice really well, and know I only send emails that are value-packed, where I share useful email insights you don’t normally find on the Internet.

So when they saw a subject line like “honey” coming from me, it created that “curiosity gap” where they just had to find out: what do I mean by “honey”? Did I accidentally send a personal email to them?

If you start using techniques like that too often, though, they will lose their effectiveness. Your subscribers will get used to them and stop trusting you. So use them wisely.

6 Email Subject Lines Do’s and Don’ts

By now, you know the core principle of how to write effective subject lines for email: create a “curiosity gap”. If you’re able to, also include a benefit or a number. Relate the subject line to the content of your email, but don’t give it all away.

You’re well on your way to becoming a subject line master, and from here on, it’s a matter of tactics and keeping a pulse on what’s working right now.

Here are a few subject lines best practices to help you on that journey…

1. Be Casual

This is contingent on your brand, but if you’re trying to build a personal connection with your readers, choose a casual tone, spoken language, and lower case for the subject line. Write the way you’d write to a friend or your mom. Leave the formalities for big brands, whose emails rarely get opened.

2. Don’t Use Exclamation Points

Just don’t. They make your emails look like you’re trying too hard, and are a cheap and ineffective way to intensify emotion. Do that with words.

Also, research showed exclamation points in subject lines negatively affect open rates.

3. Use (But Don’t Overuse) Emojis

Emojis work well in subject lines when not overused. Use them sparingly and mostly to express emotions nonverbally (vs. repeating what you already said with text in an image format).

Good examples of subject lines with emojis:

  • $100 OFF for Mother’s Day ♥️
  • We’ve Got Something For You Kasey 🎁
  • Running Facebook Ads? 👉You need this tool.

Bad examples of subject lines with emojis:

  • Don’t miss this notification gamechanger 🔔
  • Make the most out of email 📭
  • ⭐ April’s DPM Update ⭐ Are you standing out from the PM crowd? Or just blending in? Find out how you can be an awesome project manager + Loads

These are actual subject lines pulled from my inbox, even though I wouldn’t believe someone would actually use that two-line one.

4. Personalize Your Subject Line

Personalizing with information you have on your subscribers, such as first name, location, and job title can be very effective. Just don’t try to shove it in your subject line if it doesn’t belong there.

Use personalization sparingly for best results.

5. Use “Fwd:” and “Re:” Sparingly

Making your emails look like they are forwards or replies from a friend is on the border with the forbidden techniques that I described above. They can be super effective, but once you overuse them, you lose the trust of your subscribers. And trust is really hard to get back.

So use them once in a blue moon for emails you really want to get in front of more eyeballs.

6. Have Fun with Your Subject Lines!

Finally, just have fun with your subject lines. Try risky things (as long as they aren’t spammy). Try different approaches. A/B test, if you have a large enough list (but don’t worry about A/B testing if your list is smaller than 6K subscribers).

And remember that the subject line is just a part of your email funnel.

Your sender name has a huge effect on your open rate (so you need to consistently deliver quality content in your emails). The preview text should support your subject line. And the content of your email is also very important for the open rate of the next email you send.

I’d love to hear what you found the the most useful advice in this post! Jump over to the comments and let me know! Looking forward to connecting and responding to each one of you.

Kasey Luck loves helping bloggers and professionals get a life on their terms (which includes financial and location independence) by teaching how to grow their audience and email list. She runs Bold & Zesty, a blog about email marketing, and has grown three email lists by over 40,000 subscribers in total.