How to Write a Cold Email Subject Line to Boost Open Rates

So, you have an attractive offer, perfect for your ideal client, but the question remains, ‘How do you go about expressing this to your lead?’ 

Email marketing is one of the most widespread and popular forms of outreach to prospects, and a well-crafted cold email is a precious tool for garnering new clients.

Getting your subject line right is crucial. A recent study identified that as many as 47% of recipients decide to open an email based on the subject line alone.

Also, 69% will report an email as spam if the subject line doesn’t strike the right tone. So, for your outreach to be successful you need to think carefully about your subject lines.

email subject line statistics
Email subject line statistics

Throughout this article, we are going to take a look at this essential part of a cold email. Whether you use AI writing tools, a subject line generator or prefer a human touch, this guide will help you grab the attention of new prospects.

What Are Cold Emails?

Cold emails are used for reaching out to potential customers, making them aware of your business, and ideally convincing them that your offer is right for them. What distinguishes them from your usual email marketing is that cold emails are sent to the receiver without any prior contact

They are all about starting conversations and capturing the reader’s attention. This means that individually personalized messages and intriguing subject lines are key to ensuring you start the conversation on the right foot. With the email open rate at 17.6% in the US, you want to make sure that your subject line does all it can to entice the receiver into wanting to read more.


email advanced personalization
Email advanced personalization

The Basics Of Cold Email Subject Lines

Before getting into the ins and outs of creating your high-performing subject line, we’ll start by going through a few basic points to keep in mind. Highlighting the pitfalls to avoid, as well as stating some golden rules to stick to.

Don’t Use Spam Trigger Words

These are a big no-no. Most email providers have strict rules in place to ensure emails containing spam trigger words never even make it to your prospect’s inbox and go straight into their junk folder. Some common spam trigger words include:

Create Intrigue

You should create your subject line with one thing in mind: getting your prospect to open the email rather than explaining who you are or what you do. Piquing the curiosity of your email recipient is a surefire way to make them take this action. So, spending some time researching the receiver and thinking of creative offerings that appeal to them is well worth doing, that way,  you’re sure to draw them in. 

For example:

Keep It Concise

The way to grab your prospect’s attention is to include only the most relevant information in your subject line and remove any filler words. For example, instead of. The key is to use concise language as well as demonstrate that you’re not trying to take too much of your reader’s precious time. 

For example, instead of


Research shows that an email subject line that is between six and ten words has the best chance of being opened. So, keep them short and snappy to increase your chances of engaging with your prospect.

open rate by email subject line word count
Open rate by email subject line word count

Engaging Cold Email Subject Lines - Best Practices:

We’ve compiled what we see as the three key practices to consider when constructing your cold email strategy, along with a few tips and examples to give you the best chance for success.

Use A/B Testing

Getting your prospect to notice your subject line and open your email is really just about finding an effective formula and careful testing of different techniques. You can start running A/B testing with just two different subject lines and observe which performs best. You could also use cold email outreach software, which can give you an edge and help you achieve the best results.

Testing Different Techniques

There are various techniques that you can begin testing and comparing, to see what elicits the strongest response. Here are a few ideas to get you started:

1. Invite them to a meeting. Try a subject line like, “Let’s have a video chat this week.” And observe the results – potential clients often respond well to direct CTAs. In the example below you can see how the subject line clearly invites the recipient to a follow-up call.

subject line to invite
Subject line to invite

2. Use intriguing language. Instead of directly asking for a response, try a more interesting subject line that tempts your customer into opening your email, such as: “What’s the difference between these VoIP providers?”

intriguing language on subject line
Intriguing language on subject line

3. Imply scarcity. It’s not a good idea to be overly salesy in your subject line. However, the appropriate use of phrases implying a limited-time offer or diminishing stock can be an effective tool for standing out from the crowd when they’re not overused. E.g., “We’re increasing our rates soon…

You could even offer a “second chance” at a free trial or offer as in the example below.

subject line imply scarcity
Subject line imply scarcity

4. Implement direct language. Sometimes fewer words can say more and entice your audience to read on. Try short, to-the-point sentences such as:  “Tips to Improve ‘X’” or “Collaborate with us!

subject line uses direct language
Subject line uses direct language

Another consideration when it comes to your A/B testing your cold email subject lines is choosing the right leads and tailoring your strategy to what works for them. Making sure that your lead generation tactics include some of the tips outlined in this post will mean your subject lines perform better. 

You need to ascertain which prospects are actually right for you and will respond to a unique subject line they’ve not seen before. Therefore, it’s important to account for both variables when conducting your A/B testing and building your future campaigns.

Personalize For Each Prospect

When you use your prospect’s name in the subject line of your cold email, they are far more likely to, firstly, take notice of your email and, secondly, be intrigued to the point of opening it. Your potential clients are used to being bombarded with dozens of cold emails from various companies every day – you need to give them a good reason to pay attention to yours.

Generic subject line
Generic subject line

An email such as the one above isn’t going to entice your prospect to open and engage with you. It is very generic with no information that is specific to the reader.

Using your customer’s name, however, creates authority but also gives the impression that you already have a meaningful relationship with them and encourages trust. If a client reads a subject line that looks like it’s been sent to many different people, it’s an immediate ‘delete.’ However, when you use their name, you avoid this. 

In the example email below the writer has gone to great lengths to personalize their outreach. They have used the recipient’s name and also added details to the email that are specific to the reader. The recipient is less likely to ignore the email and more likely to reply.

Personalized subject line
Personalized subject line

It’s a little extra effort that goes a long way, and research actually proves that personalization can drive a 10-15% revenue lift. Demonstrating how it can also play a pivotal role across all of your email marketing strategies.


Personalize With More Than Just Your Prospect’s Name

However, personalizing your cold email subject line can mean more than just using your prospect’s name. You can experiment with using their company’s name, their industry, an interest you know they have, or a problem that those in their demographic experience.

You could experiment with the following subject lines. 

These are just some example cold email suject links that an outreach specialist from a virtual contact center might use. 

Personalization isn’t just an added extra in the consumer experience today – it’s a fundamental necessity. As the majority of companies are incorporating personalization into their marketing strategy, prospects now expect to receive personalized communications.


Main benefits from personalization
Main benefits from personalization

Ask a Question

When it comes to cold emails, the biggest difficulty is always going to be creating that immediate connection. Asking a question goes a long way toward facilitating this. 

Your prospect feels like they are being spoken to rather than spoken at, establishing an immediate sense of conversation. To give you a better idea, below we’ve listed a few ways to perfect this subject line strategy.

Ask Questions That Create Intrigue

Giving your prospect a small taste of the potential benefits of your offer is instrumental in captivating their interest. Try asking some of these kinds of questions in your subject lines:

Ask Specific Industry Questions

Combining questions and personalization. Asking questions in your subject lines that are extremely relevant to your client’s industry/interests tends to result in better performance than more general ones. Try questions such as:

If you are struggling with researching each prospect to gain relevant information to ask an appropriate question in your subject line, consider an outbound SDR. An outbound SDR is a person who initially reaches out to a prospect. 

These representatives complete the bulk of research needed to create personally relevant subject lines for each lead, allowing you to focus your efforts on leads with the highest closing potential.

Key Takeaways for Writing an Engaging Cold Email Subject Line

Remembering to be unique is a great place to start, and no matter what other suggestions you execute, keep this at the forefront of your mind. 

Ultimately, if you’re looking for areas to improve your cold email subject line just imagine how you’d feel reading it yourself. If you were a prospect, would you feel intrigued? Would you feel personally sought out? Or like just another name on a list? 

Happy cold-emailing!

To achieve the best results with email outreach, we recommend using a professional email automation software

13 best cold email platforms rated and compared

Picture of Erkki Muuga

Erkki Muuga

Erkki has over 10 years of experience as a software product manager and a proven track record in building and growing SaaS products. He has a keen eye for key differentiating factors and spotting truly valuable software features that enable business use cases.

Table of Contents

Scroll to Top