89 Effective Cold Email Subject Lines & How to Craft Them

89 Effective Cold Email Subject Lines & How to Craft Them

When you send cold emails to your prospects, you are competing with dozens of emails in their inbox.

Just imagine—there were around 300 billion emails sent in 2020. The average professional receives 126 emails per day. That’s a lot of competition!

For your cold email campaign, the primary goal should be to stand out from the crowd and make prospects open your emails.

Subject lines are undoubtedly the most crucial factor when it comes to whether your emails are going to be read or not.

In this guide, we gathered the most effective tips on how to craft a perfect cold email subject line and make people open your cold emails. We collected 89 best-performing cold email subject lines we tested and asked industry experts to share their best practices.

Let’s dive right into them!

You can take this list of best-performing cold email subject lines with you to get inspiration and fresh insights right away.
1. Make your subject line personal
2. Keep subject lines short
3. Ask questions
4. Pay attention to email snippets
5. Mention mutual connection
6. Use power words
Techniques to avoid
What about follow-ups?
Best cold email subject lines from SaaS marketers and founders
Tools to test your cold email subject lines

1. Make your subject line personal

Personalization is uber important when it comes to subject lines. This way, you can show your prospects that it’s not random spam or cold email, but something relevant to them.

I bet the first personalization option that pops up in your mind is including a prospect’s name or company name in the subject line. And that is indeed a great idea!

Besides personalizing your cold email subject lines on a basic level, you can collect even more information about your prospects before reaching out to them and use it to improve your open rates.

Here are some personalization ideas you can use in your subject lines:

  • Position
  • Industry of your prospect
  • Content they wrote
  • Common connections
  • Place you met
  • City they live/run business
  • Conference/event they attended

Adding a personal touch is your best bet to get engagement for your cold emails. However, for bigger volumes, it’s not always doable to edit all the emails manually since it could take a decent amount of time.

Fortunately, tools like Hunter Campaigns can help you save time preparing and scheduling highly-personalized emails.

Hunter Campaigns doesn’t “automate the whole process” but still saves hours of your time. It’s always better to spend a bit more time to add a personal touch to each message, even though they will be sent on autopilot.

1. Create a CSV file with detailed information about your prospects

Find information about your prospects and gather everything in a single CSV file.

CSV file with emails

2. Upload it into Hunter Leads

Hunter Leads is a simple CRM tool that allows you to structure information about your prospects and keep track on the results of your cold outreach.

If you use Hunter to find email addresses of your prospects and their personal information, there is no need to create a CSV file—you can save this info directly to Leads.
Hunter Leads

3. Use custom attributes for subject line personalization

Custom attributes allow you to easily substitute personal information about your leads in your subject lines and emails. This is one of the simplest ways to automate your outreach and be very personal at the same time.

Custom attributes for subject line
We recently analyzed 20K+ cold email subject lines that Hunter Campaigns users sent, and found out that including at least one custom attribute to your subject line boosts its open rate by more than 2%.
Average open rate for cold emails

Examples of personalized subject lines:

  • Hey {{first_name}}
  • [Your company] + {{company}} = 🚀
  • Idea for {{company}}
  • Congrats on {{event}} 👏
  • Content suggestion for {{company}}
  • Read your blog post on {{blogpost_topic}}
  • {{common_connection}} said we should connect
  • Nice to meet you at {{event}}
  • Quick collaboration with {{company}}
  • Mentioned {{company}} in my blog post
  • {{first_name}}, the link is missing
  • A few tips for {{company}}
  • {{company}} + {{our company}}
  • {{event}} in {{city}}, you invited
  • Contributing to {{company}}
You can get more fresh insights on personalized cold email subject lines on Hunter Templates. This is the biggest directory of best performing cold email templates and subject lines tried and tested by industry experts.

2. Keep subject lines short

Keeping your cold email subject lines short is probably the second most essential advice to get high open rates.

First, it’s easier to catch a prospect's attention with something short, sweet, and straight to the point. Moreover, short subject lines invoke curiosity. For example, when I receive something like “Grow Hunter with {{product}},” I don’t open the email because I know it’s promotional. But if I receive a few words with a hint, I get curious to open and read the email.

Second, your subject lines will get cut off if they are too long, especially on mobile devices. Mobile email will account for 26 to 78% of email opens, depending on your product, target audience, and other criteria. You can’t just miss out such a massive chunk of the email opens because your subject line is too long.

Just compare these two subject lines. Exactly the same message, but the first one is definitely winning in your prospect’s inbox.

Short vs long subject line examples

The same research we recently conducted at Hunter once again proved that shorter subject lines have better performance compared to the longer ones:

Average open rate for short vs long subject lines

Examples of the short and catchy subject lines:

  • Introduction
  • Congrats!
  • {{first_name}}, let’s connect
  • Potential cooperation 🤝
  • Check this out, {{first_name}}
  • You’re invited
  • Ready for {{event}}?
  • Hey 👋
  • Moving on
  • Solution for {{challenge}}
  • Trying to connect
  • Your thoughts?
  • Broken link
  • Better fit
  • Right person
  • Open position
  • Your feedback, {[first_name}}

3. Ask questions

Questions are a great way to spark interest and encourage someone to open an email.

If you ask a question relevant to your prospects, they are more likely to open your email and start looking for the answer.

It’s better to use open-ended questions since they are arousing curiosity.

For example, one of the best performing cold email subject lines I recently used is this one:

Blog post update?

As simple as that. I used it for the link building, asking prospects to update the outdated links in their articles.

Cold email outreach stats

As you can see, the open rate for my first email was 79.2%, and, for the follow-up (I used the same subject line), 47.4%.

Why does this subject line work so well?

  • It arouses curiosity.
  • It’s short and straight to the point.

Here are a few best-performing cold email subject line ideas with questions:

  • Next step?
  • Need help?
  • {{first_name}}, can we connect?
  • You ok, {{first_name}}?
  • Have you thought of {{relevant_offer}}?
  • Want to talk about {{topic}}?
  • Want to learn more about {{solution}}?
  • Collaborate? 🤝
  • Your thoughts?
  • Available for a chat?
  • Why did you go?
  • Ready to discuss {{problem}}?
  • Are you happy with {{competitor}}?
  • Do you accept guest posts?
  • New role?
  • Blog post update?

4. Pay attention to email snippets

The email snippet is the very first line of the text your prospect will see, following your subject line. Those greyish words right next to the subject line are pulled from email’s own copy.

Email snippet in Gmail

This is one of the most underestimated parts of the cold email. So many marketers think about how to optimize their subject lines and email body text, but I rarely hear that someone conducted multiple tests on email snippets.

Email snippets are essential because they impact a prospect's first impression. Together with a subject line, they catch readers' eyes and make them open your cold emails (or not).

As with any other part of the cold email, there are a few essential best practices on how to make your email snippet convert:

  • Make it relevant to the subject line.
  • Make them short and catchy (between 40-50 characters in length).
  • Include a CTA to encourage prospects to open your email.

5. Mention mutual connection

The chances that someone will open your cold email improve when you include a mention of mutual connection in a subject line.

This is one of the personalization techniques most often used when you need to send small bunches of cold emails.

Let’s say you attended the same conference or event with your prospects. In all likelihood, you don’t know them in person, but you had a chance to get the list of event participants.

Now, you can just go and mention what kind of connection you have with your prospect—you attended the same event!

Also, feel free to mention in a subject line the name of a person who is your mutual connection.

Being personal and mentioning something you have in common will definitely help you to boost your open rates during the cold outreach.

Here are a few examples of cold email subject lines mentioning mutual connection:

  • {{mutual_connection}} suggested I reach out to you
  • Nice to meet you at {{event}}
  • I hope you enjoyed {{event}}
  • {{event}}
  • Introduction from {{mutual_connection}}
  • {{mutual_connection}} recommendation

6. Use power words

Power words are words of persuasion that often evoke an emotional response and lead to the desired outcome. They engage the reader's imagination.

According to research conducted by Harvard Business Review, most people have a hard time resisting their curiosity and emotions. So strategic use of power words in subject lines makes it almost impossible for prospects not to click or read.

There are thousands of power words you can use for your cold email subject lines. SmartBlogger, actually, collected 800+ power words that convert in one place, and segmented them by different categories.

Here is our short-list of power words for cold email subject lines:

Power words for cold email subject lines

And a few examples of subject lines with power words:

  • Quick solution for {{industry}}
  • Simple tool to automate your {{process}}
  • Sharing our growth secret
  • Join private {{industry}} community
  • Key to {{company}} growth
  • Submit your expert opinion on {{topic}}
  • Sharing our best strategy on {[topic}}
  • Get lifetime access to {{product}}
  • 3 basic things you should know about {{topic}}

Techniques to avoid

There are some techniques that are better to avoid when you do cold outreach. Yes, you might have a good open rate with them (using clickbait, for example), but you will lose your points to engage at the next step, which could be a reply or direct conversion from your prospects.

1. Try to avoid mainstream cold email subject lines

There are so many cold email subject line examples around the web, so it’s tough to run out of new ideas. Especially, if you modify them and add a new perspective.

However, I noticed that some of the subject lines for cold outreach are getting overused. And every time I see them in my inbox, I understand that most likely it will be spam. Or, in better case, not personalized bulk cold outreach.

There are at least two types of subject lines that most often pop-up in my inbox:

  • Quick question
  • Appropriate person
Bad cold email subject line example

You can still have high open rates with similar subject lines. They are short and catchy, and will perfectly work for those who have never seen them. However, one of the main points for the successful outreach is to be creative and use unique subject lines that are very personal and related to your email.

2. Don’t use clickbait

It doesn’t matter if you are sending a cold or warm email—you should never use clickbait.

The chances are that your prospects open your email when you offer something outstanding. But after reading a couple of sentences of your email, it will be pretty clear that you are breaking your promise.

No matter what your promise is in a subject line, you have to confirm it with the message inside of your email.

It doesn’t make sense to create “loud” subject lines for your cold outreach campaign. In the end, what matters is a conversion rate, not the open rate of your emails.

So, please try to avoid similar subject lines:

  • This email will change your life
  • Get 10X more money in 3 days
  • One thing you need to do to become a millionaire

What about follow-ups—do I have to create a different subject line for them?

The best practice would be to use the same thread with the same subject line for your cold follow-up.

This way, prospects quickly get reminded about the offer from the previous email. Moreover, in this case, you can use follow-ups to continue telling the story or offering additional benefits.

However, you can send a different subject line for your follow-up email if the first email wasn’t opened (likely because the first subject line wasn’t as catchy).

Here is how you can set up everything with Hunter Campaigns:

  • Just keep the subject line field empty if you want to send a follow-up in the same thread automatically.
  • Add a subject line for the follow-up if you want it to be sent as a new email.
Subject line for cold email follow-up

Examples of subject lines for cold email follow-ups:

  • Our next step
  • Sending the info I promised you
  • I hate follow-ups
  • Great speaking with you
  • I forgot to mention
  • What would you say?
  • Just {{number of days}} day left
  • Nice to meet you {{first_name}}
  • Let’s take another look at {{topic}}
  • Great meeting you at {{place/event}}
  • What would change your mind?
  • Where should we begin?
  • Are you still interested?

Best cold email subject lines from SaaS marketers and founders

We reached out to a few companies who do impressive cold outreach campaigns and asked them to share their best-performing cold email subject line, together with open rate stats and thoughts on why they think it performed so well.

Here is what they shared:

Want hot conversion rate data for industry benchmarks? 🔥

Open Rate: 83%

"We used this subject link for a link building campaign to promote our new Unbounce 2020 Conversion Benchmark Report, which features AI-backed research and insights on conversion rates across 16 key industries. I think this subject line performed particularly well because it asks a clear, enticing question that builds enough intrigue without giving anything away. In other words, recipients have to open this email to get this 'hot conversion rate data' and learn more. (Plus, who doesn't want new data?!)” - Shared Ashley Luk, Marketing Strategist at Unbounce

Any insights from {{common_event}}, {{first_name}}?

Open Rate: 90%

“We used it for sales and marketing purposes to initiate a conversation with potential customers” - Shared Benjamin Thomas, Marketing Director at User.com


Open Rate: 81%

“Reactivation campaign back to old expired trials and cancelled customers. I think it really stood out because it's so short and also different from most other subject line formulas. It's also directly tied to the purpose of the email and the intentions are clear.” - Shared Corey Haines, Head of Growth at Baremetrics

👋{{brand_name}}’s on Sumo!

Open Rate: didn't track

“We're sending these emails to brands and companies we mentioned in both Sumo and AppSumo blog posts. The subject line is personalized with the company's name, and saying it's on Sumo or AppSumo picks the interests of the receivers to check it out. We don't ask for backlinks right away in the email — instead, all we do is sharing the blog post with the team. It's always more valuable to build long-term relationships compared to a one-time transaction.” - Shared Dean Yeong, Head of Content at Sumo

The most exciting opportunity for companies in 2020 (and beyond)

Open Rate: 90%

“A key piece of content for us was ranking in position #3 in the Google search results, but we knew it deserved the #1 spot. So, we launched an outreach campaign targeting popular industry blogs that cover similar content, but lacked original research.

This subject line captured the reader's attention and piques curiosity. Not only did we earn one of our highest open rates for a cold outreach campaign, but we landed several high quality, relevant links and with weeks, our content had moved up and earned that #1 ranking.” - Shared Steven Macdonald, Digital Marketing Manager at Super Office

Read this email if you need XYZ

Open Rate: 37%

“It was used for sales outreach. This subject line works because it creates curiosity, and is highly relevant to the prospects.” - Shared Gaetano DiNardi, Director of Growth Marketing at Nextiva

🤝Let’s keep it between us, {{first_name}}!

Open Rate: 63%

“We used this subject line for link building. The reasons why I feel it had great success are that it is abstract (everyone loves secrets and this subject line triggers that emotion), non-salesy,  and personal (we used the first name attribute).” - Shared Vijay Khandekar, Inbound Marketer at GorillaDesk

Hi, {{first_name}}

Open Rate: 60%

“Generating leads was our purpose. It had great success definitely due to the first name that was added directly in the subject line. It stands out from the rest of the emails and it's more personal.” - Shared Roxana Motoc, Marketing Manager at SocialBee

Get more best-performing cold email subject lines ideas shared by industry leaders

Tools to test your cold email subject lines

  1. Use Moosend’s or CoSchedule’s subject line testers to get general insights on what to improve.
  2. Preview your subject line in user’s inbox with Zurb (you can also check the email snippet there).
  3. Analyze how emotional your subject lines are and if they have any power words with Advanced Marketing Institute.
  4. Check the readability of the subject line copy with Hemingway or Grammarly.

Wrap up

The subject line that works for all cold email campaigns doesn’t exist. It’s all about dozens of tests, relevance to your business, and a bit of creativity.

I’m pretty sure that the tactics mentioned in this guide will help you to craft a perfect subject line and skyrocket your open rates.

Have questions or feedback? Don’t hesitate to ping me on Twitter or drop a few lines at irina@hunter.io.

Irina Maltseva

Irina Maltseva

Head of Marketing at Hunter. I enjoy working on inbound and product marketing strategies. In spare time, I entertain my cat Persie and collect airline miles.

Don't miss the next updates

Get more insights on cold email outreach, sales and marketing directly to your inbox. Once a month.
✕ Close

Would you like to receive more posts like this, once per month?