89 Effective Cold Email Subject Lines & How to Craft Them

When you send cold emails to your prospects, you're 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.

What makes a great cold email subject line?

While there are a lot of effective subject lines out there, most share a few traits that help them generate great results. A good subject line is:

• Short – You want to keep your subject line short to make sure it doesn’t appear cut off in your recipient’s inbox. Most email providers show up to 60 characters of a subject line, so try to stay under that limit.
• Personalized – The best way to grab prospects’ attention and get them to open your email is to personalize the subject line. You can mention the prospect’s name, company, or a challenge they’re dealing with.
• Urgent – Finally, you’ll want to make your email seem time-sensitive to motivate recipients to open it sooner rather than later. You can do this by adding a sense of urgency to your subject line.

Now that we got that out of the way, let’s look at our top tips for crafting great cold email subject lines and the examples you can use in your own campaigns.

1. Make your subject line personal

Email subject line personalization is crucial to developing successful email marketing campaigns. By personalizing your subject line, you show prospects that your email is not random spam, but something that's actually relevant to them.

I bet the first personalization option that pops into 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:

• Job role
• Industry
• Content they wrote
• Common connections
• Place you met
• The city they live in
• Conference or event they attended

Adding a personal touch is your best bet to get engagement for your cold emails. However, when sending a large volume of emails, it’s not always doable to edit all the emails manually since it could take quite some 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.

Here's how to use Hunter Campaigns to automate personalized cold email outreach:

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

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

2. Upload it to Hunter Leads

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

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.

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}}

2. Add value

What goes through people’s minds when deciding whether to open an email can be boiled down to: “What’s in it for me?”

If your subject line doesn’t immediately show that the email can provide some sort of value to the recipient, they’re unlikely to open it.

Find resources that can be of value to your prospect, and use the subject line to hint at the email containing these resources. This will help your email stand out in the inbox.

Make sure the resources are highly relevant to your prospect and their current pain points, though.

If you provide prospects with something that can help them solve a problem they’re dealing with, they’ll be a lot more likely to both open and reply to your email.

Even if they don’t reply to your first email, you’ll leave a good impression on them by focusing on providing value. This will make it more likely that they’ll engage with any future emails you send them.

Examples of subject lines that focus on value:

• Resources that can help {{Company Name}} right now
• X tips to help solve {{pain point}}
• Ideas for {{goal}}
• {{X}} steps to reaching {{goal}}
• A better way to solve {{pain point}}

3. Keep it short

Keeping your cold email subject lines short is one of the best things you can do to ensure high open rates.

First, it’s easier to catch a prospect's attention with something short, sweet, and straight to the point. Moreover, a short subject line invokes 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 enough to open and read the email.

Second, your subject lines will get cut off if they're 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 on such a massive chunk of email opens because your subject line is too long.

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

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

Examples of 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}}

4. Arouse curiosity

People are curious by nature. If you hint at something without providing all the details, we have a natural urge to try to learn more.

You need to make the recipient curious about the content of your email if you want them to open it.

Don’t give away all the information in the subject line. Make them open the email to learn more.

You can do this by asking a question, hinting at a solution to the prospect’s problems, or saying something unusual.

Here are a few examples of subject lines that arouse curiosity:

• It’s really easy to reach {{goal}}
• What your competition does to stay ahead
• {{Name}}, you’re invited
• {{Name}}, can you keep a secret?

5. Ask questions

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

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

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 link building, asking prospects to update the outdated links in their articles.

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%.

Here are a few 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?

6. Pay attention to email snippets

The email snippet is the second line of text your prospect will see, following your subject line.

This is one of the most underestimated parts of a cold email. So many marketers think about how to optimize their subject lines and email body, 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 the subject line, they catch readers' attention and make them open your cold emails (or not).

As with any other part of a 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 it short and catchy (between 40-50 characters in length).
• Include a CTA to encourage prospects to open your email.

7. Mention a mutual connection

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

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!

If you have a mutual acquaintance with the prospect, you can try mentioning them too.

Being personal and mentioning something you have in common with the prospect will definitely help you boost your open rates when doing cold outreach.

Here are a few examples of cold email subject lines mentioning a 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

8. Use power words

Power words are words of persuasion that often evoke an emotional response and lead to a 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 collected 800+ power words that convert and divided them into categories.

Here is our shortlist of power words for cold email subject lines:

A few examples of subject lines that use 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 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 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
  

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 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're breaking your promise.

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

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 follow-up email.

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.

Examples of subject lines for follow-up emails:

• 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:

"We used this subject line 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?!)” - Ashley Luk, Marketing Strategist at Unbounce

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

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

“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 piques the interest of the receivers to check it out. We don't ask for backlinks right away in the email — instead, all we do is share the blog post with the team. It's always more valuable to build long-term relationships compared to a one-time transaction.” - Dean Yeong, Head of Content at Sumo

“A key piece of content for us was ranking in position #3 in 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 piqued 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 in weeks, our content had moved up and earned that #1 ranking.” - Steven Macdonald, Digital Marketing Manager at SuperOffice

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

“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).” - Vijay Khandekar, Inbound Marketer at GorillaDesk

“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.” - Roxana Motoc, Marketing Manager at SocialBee

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 the users' 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's tool.
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.