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Cold Email Subject Lines: 7+ to Boost Open Rates

The first thing a prospect sees when an email lands in their inbox is the email subject line. If it fails to catch your prospect’s attention, they probably won’t open the email.

Email marketing often plays an integral part in a company’s marketing strategy, so getting a high email open rate is extremely important. Cold emails are often the first touchpoint sales reps have with potential customers and offer a chance to make a good first impression. Achieving high open rates involves crafting the best cold email subject lines to get results.

Depending on your industry, benchmark data from MailChimp shows email open rates can fluctuate between 15% and 28% based on a subject line, so it’s crucial that you write one that grabs attention.

The good news is there’s a process that will help you create eye-catching copy for your email subject lines. By integrating personalization, urgency and intrigue into your subject lines, you can increase the chances that your emails will be opened.

In this guide, we’ll look at the science behind cold email subject lines and share how to write attention grabbing subject lines that boost open rates.

Table of contents

The science behind cold email subject lines and open rates

Great subject lines, especially in cold emails, pique curiosity and make your email list recipients want to learn more. As Dipak Vadera, Sales Manager at Leadfeeder, puts it: “If you want to stand out from the other hundreds in a prospect’s inbox, you need to start with the subject line.”

The best way to perfect your email subject lines is to test different strategies to find out what hooks your target audience’s interest and alter your copy based on your findings.

During his time as Director of Marketing at LeadGenius, William Wickey took a deep look at how subject lines impact cold email open rates. LeadGenius’s approach was to go beyond a simple A/B test. Instead, they went through several rounds of iterations to discern which changes achieved the best results.

The outcome? Their open rate jumped from 37% to 86%.

The best-performing email subject lines from the study were:

  • “Your sales process”: 37.5% opened

  • “Sample leads for [company]”: 50.6% opened

  • “Potential leads for [company]”: 61.1% opened

  • “Found you on LinkedIn”: 64.6% opened

However, there was one subject line that netted the company an 86.6% open rate, an incredible percentage for any cold email campaign:

“I found you through [contact_first_name] [contact_last_name]”

The reason this particular email was so successful? Because it built upon existing connections and credibility; it’s clear the sender put in the effort to ensure this prospect was a good fit. When targeting decision-makers, this level of care goes a long way.

However, the importance of an email’s subject line goes beyond attracting the reader. A subject line can also impact whether or not your email is marked as spam or promotional. These factors can be influenced based on word choices, character count and even email emojis.

Factor 1: Pay attention to the character length

A great email subject line takes form into account. Your email subject line length matters because of how it’s displayed across different devices.

People are constantly on the go, spending less time reading emails at their desks. Roughly 46% of emails are now opened on mobile devices with varying operating systems, such as iOS tablets, iPhones and Android smartphones. This smaller screen space significantly truncates subject lines, a fact that marketers and salespeople can’t afford to ignore.

To complicate the matter, exactly how many preview text characters are displayed, on both desktop and mobile, depends on what email client the receiver is using, while character length limits in subject line fields can vary considerably across Windows and MacOS.

Backlinko analyzed 12 million emails to find out, among many things, what the ideal length for a subject line is. Founder Brian Dean concluded subject lines between 36-50 characters get the best response rate:

For short subject lines in the 1-15 character range, it’s difficult for a prospect to know what your email is about. Therefore, make your email subject lines as specific as possible to set the right level of expectation.

Factor 2: Avoid being marked as spam

Even the most carefully constructed email subject lines go wasted if they are marked as spam by different email clients. Seeing your emails in their Gmail, Hotmail/Outlook.com, Yahoo or Apple iCloud spam folder might even lead your email subscribers to unsubscribe.

According to Mailigen, there are several reasons why emails get flagged as spam. Each spam filter looks for different criteria, but on average, they evaluate emails by their campaign metadata, embedded content and format, underlying code and IP address.

The best way to avoid your cold email ending up a raised flag in junk mail is to avoid using trigger words. Yesware’s Melissa Williams says you should avoid words such as “free”, “money”, “help” and “reminder.” Here’s a full list of trigger words Williams recommends leaving out of subject lines:

Factor 3: To emoji, or not to emoji?

Including email subject line symbols like emojis and emoticons can either positively or negatively impact your email open rate, depending on how you use them. If implemented correctly, using symbols (for example, smiley faces and special characters) can help you portray emotion and stand out in your prospect’s inbox, while in other cases, email subject line symbols can come off as looking unofficial or scammy.

In research conducted in 2017, Phrasee found that 5% of global subject lines included an emoji symbol. The study also involved testing emojis in 14 email marketing campaigns, involving 10 randomly selected groups of roughly 50,000 email recipients.

The study found that 60% of the time, emojis had a positive effect on an email’s subject line:

In these use cases, the emojis and email symbols were contextually relevant to what the content was illustrating. For example, a subject line where Domino’s Pizza asks users which flavors are most appealing would benefit from using a “yummy face” emoji to represent hunger and pleasure. As long as the email subject line symbols are on-brand and relative, it’s likely to be effective.

However, inserting an emoji randomly into a subject line can make an email appear spammy or like clickbait. The study found that these overused tactics can seem misleading and too hard-sell, potentially turning off prospects.

Just like the words we use to craft subject lines, emojis must be used in the right context and have a purpose (for example, using envelope symbols and heart and flowers emojis on Valentine’s Day). If it helps to explain the email content and grab attention, then it’s likely the email will get opened.

If you’re eager to use emojis or email text symbols in your next relevant email campaign, but are unsure of the emojis available, you can refer to a site like emojipedia which documents the meaning and common usage of emoji characters in the Unicode Standard.

Heat Up Your Cold Emails With 25 Customizable Email Templates

These cold email templates sourced from Pipedrive sales experts will help you scale your prospecting, drive more replies and stay out of those trash folders.

How to write cold email subject lines

Writing cold email subject lines that boost open rates comes down to having a plan.

Remember, you’re emailing somebody who doesn’t know you. Ask yourself: “Would I open this email if a person I didn’t know sent it to me?” The best way to overcome this problem is by making the email subject line clear and curiosity-inducing.

Will the subject line make your reader curious?

The key with a subject line that arouses curiosity is not to give too much away. If you do, a reader may decide they’re not interested in what you have to say and ignore your email completely, never seeing your email body content.

An effective email subject line that sparks curiosity could be:

“I wanted to share my ideas with you.”

Does the subject line create a sense of urgency?

Ever wondered why emails that promote flash sales and important alerts work so well?

Subject lines with words that imply time sensitivity are proven to increase email open rates. A MailChimp study looked at four words (“urgent”, “breaking”, “important” and “alert”) and the impact they had when they were inserted into an email subject line. Just another example where A/B split testing different subject lines and trusting the data can help with the effectiveness of your cold call email subject lines.

The results were clear: all four significantly improved open rates:

An example of a subject line with urgency could be:

“URGENT: Get this now before it’s too late!”

Not every email you write needs urgency or time sensitivity to boost open rates, but it’s an exciting way to promote content, offers and updates every now and then. Use it sparingly and this technique will spur excitement in your prospects.

You’ll remember that “urgent” is in the table of trigger words above.

It’s important to find the balance between avoiding the spam folder and making your subject line eye-catching. Only use urgency infrequently and when it’s relevant to avoid your emails getting marked as spam.

Is the email subject line personalized?

Personalizing content is a great way to catch a prospect’s attention and stand out from other low-effort email subject lines that have surely flooded their inbox. Kyle Racki, CEO at Proposify, suggests:

“We’re now programmed to ignore emails that are obviously generic mass emails. One way to stand out in someone’s inbox is to make the subject line and the opening line customized to them as a person.

“The subject line should be thought of kind of like a headline: don’t give away the punchline, but create intrigue enough for them to open the email.”

A report by Yes Lifecycle Marketing found that personalized email subject lines can boost open rates by 50%. Personalization can go beyond highlighting the recipient's name or company. You can also write subject lines that align with a prospect’s likes, dislikes, demographics or behavior.

When Spitfire Inbound was marketing a new Suzuki Swift, they used a hyper-targeted, personalized email subject line to boost their open rates to 70.5%. This is what their prospects saw when the email landed in their inbox:

“Be the first to find out more about the new Suzuki Swift?”

This tactic gave users who had previously inquired about the Swift a sneak peek into the new product. By providing this small-group access to privileged information, it made the recipients feel special.

Personalization like this generates interest, excitement and, ultimately, action.

Does the subject line link to a cultural theme?

Inserting movie or music references into your content is a clever way to capture attention. Pop culture mentions can also boost relatability and make your email stand out.

The key is to use a well-known or topical cultural theme that aligns with your target audience, and it’s even better if you can riff on something current (perhaps also using email text symbols and a relevant emoji).

For example, if there’s a James Bond film coming out and you’re confident that it’s likely to resonate with many of your ideal customers, you could try the following to introduce your company in a cold email:

“[company name], license to [USP]”

Or, with a new Lord of the Rings TV show coming to Amazon, you could try this to announce a new product:

“One [Product] to rule them all”

7 cold email subject line examples to boost open rates

Let’s take a closer look at how we can put the aforementioned advice into action with seven detailed examples.

1. “Did you know that we have [fact] in common?”

As shown earlier, getting a prospect to open a cold email often relies on it piquing their curiosity. However, an essential part of the sales journey is building a relationship with a prospect.

This subject line attempts to do both at the same time.

The shared fact may be that your companies are using the same piece of software. Or, it could be a personal common interest. Any fact you find in common with a prospect, no matter how small, can help you stand out in their inbox.

You can use things like:

  • Birthdays/anniversaries/milestones
  • Interactions with your social media/website/brand
  • Mutual interests
  • Geographical location

The easiest way to find out a prospect’s birthday, shared interests and location is to utilize tools like social media. From there, you can collect data points and create bespoke subject lines to help you stand out in a prospect’s inbox.

2. “I’d love to give you some advice on [topic]”

One of the best ways to win prospects over in cold emails is to show them that you care about their business.

Offering to help them can fast track that process. People are always interested in free knowledge, so find a part of their business where you can help them improve.

Before sending an email out with this subject line, make sure you have a clear goal for its outcome:

  • Do you want to start a conversation?
  • Are you looking to sell a product?
  • Are you trying to build a relationship that will lead to a future partnership?

The subtle differences in your goals will decide what topic you insert into your email subject line. If you’re looking to start a conversation with a prospect, keep it casual and talk about shared interests such as sports or traveling (again, you can use social media for help here). If you’re looking to sell, try asking them about a service or product you’ve noticed that they’re using while you’ve been prospecting.

A good email subject line indicates the value and communicates what they’re going to get. The best way to pique interest is by offering the prospect helpful information.

3. “Hey [first name] – [Question]?”

Personalizing your cold email subject lines with a prospect’s name has shown to boost open rates by 20% in case studies.

Personal subject lines can go a step further by adding a quick question. Here, you can use a question to plug your product or service directly. For example, if you’re in the SEO industry, your subject line might look like this:

Hey [First Name]—want to see your content on Google’s first page?

Of course, it’s impossible to send out an email like this without doing some homework on the prospect’s business. The more you know about them, the easier it’ll be to target their goals and interests in your question.

The only way to perfect this is to experiment. A/B test your subject line personalization email to see which one brings better results, then continue to iterate until you reach optimal open rates.

Remember, make sure the question is authentic and personal. Anything that isn’t targeted towards a prospect’s business goals will end up in the trash

4. “A way for [prospect company] to end [problem]”

Every prospect has a problem to solve. A great way to connect with the reader is to specifically address these issues and explain how your solution can solve them.

Addressing a pain point your prospect has is also a good opportunity to pique their curiosity:

“I’ve found a solution for [pain point]”

Look for prospects who fit your customer persona on platforms like LinkedIn, then highlight the problems that you solved for similar customers, outlining how you can do the same for them.

Whether that’s lowering their operating costs or getting them more customers, make sure you highlight their most painful problem in the subject line. At the very least, they might want to read what you have to say.

5. “I noticed you were looking at [page]—can I help?”

One of the best modern sales tech features is the ability to track potential customers and their unique interactions through your website with tools like cookies, webhooks and chatbots.

If a visitor looks at products or your pricing page but leaves without purchasing, that creates a follow-up opportunity. However, emailing with a “did you forget something?” subject line is generic and doesn’t entice the prospect to open your email. Instead, personalize it to the page they were browsing.

For example, you can highlight products based on criteria like shopping history. By sending specific rather than routine automated inquiries, you can show users that you put the effort into learning about their needs.

A follow-up email like this conveys that you want to help them through their customer journey. A touch of personal service in this circumstance may be the magic touch that motivates buying behavior and encourages your customer across the finish line.

6. “[Name of mutual connection] suggested I reach out to you”

Highlighting a mutual connection when sending out cold emails is a great way to get them noticed and opened.

Pointing out this shared connection helps you to overcome the detached nature of cold outreach. As well as adding the name of the mutual connection, you can also add in a recent conference or event you’ve both attended.

This referral technique will really drive the point home that you're not a robot and that you have something to say that’s worth listening to.

7. “Act quickly! Offer on [product name] ends tonight.”

Marketers and salespeople alike know urgency helps boost sales. One reason is that customers hate missing out on a good deal. Although using words to suggest limited-time deals and offers can land your sales email in more spam folders, it may also get you a higher open rate from your email subscribers. As with every cold email strategy, the important step is testing to see what works best for you.

You’re probably familiar with the phenomenon FOMO, or “fear of missing out.” For instance, a subject line and email copy that communicates the urgency of an expiring deal on a product can trigger FOMO that will push email recipients to grab their last chance to purchase, increasing ecommerce conversion rates within a short timeframe.

According to Eventbrite research, FOMO is on the rise, especially within the millennial demographic. According to one survey, 60% of millennial consumers said they make a reactive purchase, often within 24 hours, after experiencing FOMO.

Entrepreneur Ramit Sethi has made urgency, particularly urgent subject lines, a core part of his email sales strategy. His five-day email funnel that uses urgent subject lines netted him $400,000 worth of sales during a product launch. His final urgent subject line looked like this:

The trick to using urgency isn't to make every email message imperative. However, if you’re offering a limited-time product, or launching a new feature, or promoting a sale like Black Friday, it’s a perfect time to roll out this technique.

Final Thoughts

Email marketing has proven to be one of the most effective tools available to businesses. It helps build valuable relationships with customers and close deals with prospects.

However, cold emails, even those written using cold email templates, can only be effective if your prospects are opening them. The key to improving that click-through-rate (CTR) is to write enticing, personalized email subject lines that catch the reader’s attention and make a good first impression.

And don’t forget about the smaller details that go into writing an effective cold email subject line. Make sure to follow best practices to avoid the spam folder.

The key is to iterate often, analyze results and make necessary changes. Follow this formula to craft the best email subject lines and watch your open email rates soar.

Heat Up Your Cold Emails With 25 Customizable Email Templates

These cold email templates sourced from Pipedrive sales experts will help you scale your prospecting, drive more replies and stay out of those trash folders.

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