100 Cold Email Subject Lines To Guarantee a Response

By Dmitry Dragilev 6 Comments Last updated on November 8, 2017

One of the challenges email marketers face today is making sure their messages are actually being read.

Emails are an integral part of modern day life, with over 206 billion messages sent every day.

With so much correspondence flying around, it’s nearly impossible to predict whether yours will be opened or trashed.

But if you write a powerful email subject line…

Then you’ve won half the battle.

Subject lines can make all the difference between creating a viable lead or your address ending up on a block-email list.

As such, it’s more vital than ever to make sure you’re nailing subject lines every time.

To help, I’ve teamed up with Lucy Literado of Reply.io to analyze 100 examples across a variety of industries.

In this post, you’ll:

  • See examples and best practices of subject lines for inbound, outbound and customer emails
  • Learn essential principles to create your own attention-grabbing subject lines

How to craft cold email subject lines that stand out

Before we get to the examples, take a moment to familiarize yourself with these tips for creating powerful subject lines:

Keep it short and sweet

It can be tempting to cram as much information as possible into your subject, making sure you spell out every single point that’s in the message.

However, concise subjects are more likely to hook readers. Remember, most email clients will cut off the subject line after a small number of characters, so make each word count. There’s no room for fluff here!


Personalize, Personalize, Personalize

One of the biggest challenges in any kind of email campaign is making the message personal and relatable.

At the most basic level, you can use the recipient’s name.

At a deeper level, make sure the subject appeals directly to that customer, to their interests and to the challenges they face. By carefully segmenting your list, you can tailor the subject line and email to very specific groups.


Give them a reason to click

Any successful subject line works by giving the reader a reason to read more…

There are two key ways to do this:

First, outline the email’s contents–whether it’s a special offer, a case study or a unique message.

Then, create curiosity–ask a question or make a statement that’s designed to grab the reader’s attention.


Highlight urgency

Sometimes an email will sit in my inbox for months without being opened. The subject line looks interesting, and I’m sure it’ll be worth reading.

But with a million and one things already on my to-do-list, it’s easy to save emails for tomorrow.

So, if you can, give readers a reason to open your email immediately.

For example, if the offer ends tomorrow, or if there are only 5 seats left for your conference, then highlight this in your subject line.


Use testing to optimize results

The truth is you can create good subject lines by using these principles, but creating great subject lines requires testing.

A/B split testing will help improve your subject lines and ensure that they’re working for your audience.


For effective A/B testing, only change and test one piece of the subject line at a time, otherwise, you can’t be sure what worked and what didn’t.


Now that we’ve covered some of the key principles, let’s crack on with 100 examples!

As you read these, take the time to see how they use the previously outlined principles, so you can do the same with your own subject lines.

NOTE: This entire post is worth reading from beginning to end. However, you can also jump to specific categories in the table of contents:


Curiosity-based subject lines primarily target our emotional need to close an open loop.

You can’t help but want to check out what the email is all about.

You’ll notice these subject lines don’t appeal to our logical brain.

The subject will tell you nothing about the contents of the email and how it will be useful to you. And yet you’ll feel compelled to open it on a busy day!

However, make sure the body of the email lives up to its promise!

Nothing is worse than opening an email that’s not even half as interesting as the subject.

Avoid clickbait, and use this rule judiciously.

Here are a few great examples:

Subject line: Are You Prepared for This?

  • Sender: JivoChat
  • Type: Outbound
Dmitry and Lucy's take

This subject raises curiosity levels straight through the roof, while also incorporating fear-based motivation.

Preparation implies a change is around the corner.

This sparks readers’ interest and ignites fear of being unprepared for an important event.

2. Subject line: How would you answer this question?

  • Sender: WorkRails
  • Type: Outbound
Dmitry and Lucy's take

This is a clear example of creating an open loop and raising curiosity in readers’ minds. To find out what the question is, you’ll have to open the email.

More than that, the subject asks the recipient to formulate an answer to this question, demanding more of their focus and attention.

3. Subject line: Looking to Learn More?

  • Sender: WriterAccess
  • Type: Outbound
Dmitry and Lucy's take

Here’s another headline that provokes curiosity:

Who wouldn’t want to learn more?

4. Subject line: It’s not big. But it is clever

  • Sender: Radir Ltd
  • Type: Outbound
Dmitry and Lucy's take

A clever play on a well-known phrase stands out and arouses curiosity.

It can be risky in outbound messages where recipients aren’t aware of your company. But the cold email subject line does enough to make you stop and look twice.

5. Subject line: Why we don’t want to fill your vacancies

    • Sender: Sigma Recruitment
    • Type: Outbound
Dmitry and Lucy's take

This works by going in the opposite direction of readers’ expectations.

Why wouldn’t a recruitment company want to fill your vacancies?

The apparent logical inconsistency grabs attention and encourages recipients to click through to find the answer.


6. Subject line: *Don’t Open This Email*

  • Sender: Manicube
  • Type: Online example
Dmitry and Lucy's take

You can’t help but love this reverse psychology.

It speaks to innate curiosity and our overwhelming desire to do what we’re told not to do.

Have you ever wanted to touch something after reading a ‘Don’t touch!’ sign? It’s practically wired into our DNA.

However, this is another one I’d use sparingly.

Used once, and it’s charming. But the second time around makes it seem like a cheap gimmick.

And if the contents aren’t worthwhile, or explain why the reader shouldn’t have opened the email, then they’ll feel tricked.

Remember, nobody likes to be tricked.

7. Subject line: utm_medium=email&utm_campaign=jun2017&utm_source=just-landed

  • Sender: Auto Pilot
  • Type: Inbound Opt-in
Dmitry and Lucy's take

Auto Pilot knocked the curiosity factor out of the park on this one.

While it may look like a mistake at first, the email quickly explains that the ‘jumbled string of text and symbols is what UTM parameters look like, and they’re super important for tracking marketing ROI.’

It’s a risky move, and I wouldn’t try this in a cold email. But as an email to an opt-in list of tech-savvy marketers, it certainly stands out.

What’s a similar way to make a subject line stand out in your industry?

8. Subject line: Bad SEO Advice

  • Sender: Backlinko
  • Type: Inbound Opt-in
Dmitry and Lucy's take

I love subject lines that switch things up and start from a negative.

When good advice is a dime a dozen, bad advice stands out and kicks the curiosity factor up.

I refer to this as the ‘glossy mag headline.’ Next time you’re out and about, take a look at what’s on the magazine covers.

Positive messages might be nice, but messages about mistakes sell more.

What negative aspect of your industry can you highlight?

Try ‘Bad {your industry} Advice’

9. Subject line: It finally happened

  • Sender: ProductHunt
  • Type: Inbound Opt-in
Dmitry and Lucy's take

Wait, what finally happened? Is it good? Bad? Am I affected?

Turns out it only takes three words to raise your reader’s heart rate, along with their curiosity.

10. Subject line: Answers and Mistakes

  • Sender: Lincoln Murphy
  • Type: Inbound Opt-in
Dmitry and Lucy's take

We all want answers. And we have an insatiable appetite for seeing other people’s mistakes (remember the ‘glossy mag’ principle?).

So for those on Lincoln Murphy’s list, this subject created enough curiosity to get readers clicking.

11. Subject line: Increase your productivity with ROBOTS!

  • Sender: ProductHunt
  • Type: Inbound Opt-in
Dmitry and Lucy's take

Like my aversion to all lower caps sentences, I’m normally against yelling in ALL-CAPS.

But when you have a cool topic like robots, I think that’s something worth shouting about.

Product Hunt offers a clear value proposition (increased productivity) with a dash of the unexpected (robots).

12. Subject line: {Your Name} in 2017!

  • Sender: Ed Gandia
  • Type: Inbound Opt-in
Dmitry and Lucy's take

This is an example of a subject that uses personalization in a succinct format.

This was sent shortly after the new year when people are often thinking about what’s in store for them in the future.

Remember: Sometimes an email’s timing is as important as its contents.

13. Subject line: You are not alone

  • Sender: Leah @ FTFP
  • Type: Inbound Opt-in
Dmitry and Lucy's take

Sean Platt has written a post on CopyBlogger about how this is his most opened subject line by far.

The post is well worth a read, but the gist is that we all share a fear of being alone.

So this will speak to your readers’ sense of belonging.

14. Subject line: Circle this date and preorder the champagne

  • Sender: Donald Miller, StoryBrand
  • Type: Inbound Opt-in
Dmitry and Lucy's take

Donald Miller uses this subject to elicit the recipient’s interest.

Rather than simply stating an important date is coming up, he finds a fresh way to illustrate its importance.

Taking the time to find illustrative ways to share announcements ensures your messages won’t grow stale.

15. Subject line: Uber for Dogs

  • Sender: CBInsights
  • Type: Inbound Opt-in
Dmitry and Lucy's take

Here’s an example of an understood concept, Uber, mixed with a metaphor about dogs that likely sparks curiosity.

Are you as curious as I am to find out more about an Uber for dogs?

16. Subject line: [Classified] Secret Project…

  • Sender: Kai Davies
  • Type: Inbound Opt-in
Dmitry and Lucy's take

This is a mysteriously playful subject line.

And maybe it’s all the time I’ve spent watching James Bond films, but when this showed up in my inbox, I had to click it.

Involving your recipients in something exclusive and mysterious will pay off in higher open- and click-through rates.

Asking a Question

The quickest way to get someone’s attention is to ask a question.

Questions work well because they’re interactive.

When you ask a question, readers automatically begin to think of answers.

Here are a few examples of this in action:

17. Subject line: How do you plan to scale?

  • Sender: Nick Stephenson
  • Type: Inbound Opt-in
Dmitry and Lucy's take

Here’s an example of another great question.

The sender could have asked a straightforward yes/no question:

‘Do you plan to scale?’

Instead, he asks ‘how’ do you plan to scale.

This requires more thought and implies you should have a plan in place.

18. Subject line: Content Strategy: Is Your Content a Mess?

  • Sender: Clearvoice
  • Type: Inbound Opt-in
Dmitry and Lucy's take

‘You’ is a magic word in marketing, and Clearvoice gives us a classic example.

They’re speaking directly to their readers.

We’re not hearing about random people’s content issues, only our own. That’s powerful.

They’re also tantalizing readers with a fear-based message, a strong motivating factor to take action.

19. Subject line: Stuck in a Facebook ad rut?

  • Sender: Jo at Copyhackers
  • Type: Inbound Opt-in
Dmitry and Lucy's take

This question works by appealing to a specific problem.

If a recipient is experiencing this problem, if they look at the subject line, and say, ‘Yes, yes, I am…’

Then, they’ll be more likely to open the email, because the writer implies a solution.

20. Subject line: How can I help?

  • Sender: Kai Davies
  • Type: Inbound Opt-in
Dmitry and Lucy's take

When so many emails are all about selling, an email that’s completely focused on offering help, with no costs or strings attached, stands out.

The sender gets to know what problems affect their audience and can form closer relationships with prospects.

And the receivers get free advice.

It’s a win-win.

21. Subject line: Need help?

  • Sender: Ed Gandia
  • Type: Inbound Opt-in
Dmitry and Lucy's take

If you tell someone you can help, they’ll likely want to know how.

22. Subject line: How many stars would you give ‘{recent purchase}’?

  • Sender: Amazon.co.uk reviews
  • Type: Customer
Dmitry and Lucy's take

Reviews are an important aspect of Amazon’s business:

Have you ever bought something on Amazon without reading the reviews?

But getting people to actually write a review isn’t so simple.

To increase the likelihood of someone leaving a review, Amazon starts off with a subject line that asks you how many stars you’d give a recently purchased item, rather than write a review.

If you have to ask for something, make it a small request, something the recipient can easily say yes to.

23. Subject line: Time for a career change?

  • Sender: Tough Mudder
  • Type: Customer
Dmitry and Lucy's take

While Tough Mudder puts on obstacle races around the world, they also know their audience is made up of people who are looking for adventures.

That’s why, when they’re looking for potential employees, they’re able to use subject lines like this to appeal to their tribe.

24. Subject line: How’s it going with Calendly?

  • Sender: Calendly
  • Type: Customer
Dmitry and Lucy's take

Have you ever been out for a meal and had the waiter ignore you after taking your order?

Instead, they’re normally around after a few minutes to check if everything’s okay.

Calendly follows this pattern, making sure their customers are happy with the service so far.

It’s a great opportunity to get feedback and make sure customers are getting the best from them. And the subject line is direct and to the point.

Being sent soon after signing up, but after enough time has passed for the customer to try out the service, and an easy-going informal tone contributed to this email’s massive open rate.

What do your customer follow-up emails look like?

Try using ‘How’s it going with {your product/service}?’

Social Proof

In an ideal world, people would make purchases by evaluating a product rationally.

But you know that rarely happens.

In the real world, people make decisions based on social proof:

What are other people saying, doing and buying?

People want a quick way to validate that the offering works, and the easiest way to do that is to hear from people that have already used it.

Social proof is one of the most powerful persuasion triggers used by marketers.

25. Subject line: Lucy, join over 24,000 businesses funding their next step

  • Sender: Funding Circle
  • Type: Outbound
Dmitry and Lucy's take

Funding Circle uses personalization by using recipients’ first names, then adds social proof to grab attention. If it’s good enough for 24,000 businesses, surely it’s worth checking out?

Using ‘join’ as a verb is also a good move, inviting the reader to be a part of a large community of businesses.

26. Subject line: #1 rated overall for home security

  • Sender: Protect Your Home
  • Type: Outbound
Dmitry and Lucy's take

This straightforward subject line focuses on ratings.

If your service or product has been given any awards or ratings, then highlighting them in the subject line can convince recipients to learn more.

27. Subject line: Thousands join this webinar every month. Why haven’t you?

  • Sender: Sumo
  • Type: Inbound Opt-in