How We Write Cold Email Subject Lines That Get Cold Hard Results

A guest blog by Will Cannon (Founder & CEO of UpLead)

Writing cold emails that get opened, let alone convert, is very challenging, simply because you’re sending those to strangers. Without an established relationship with your cold targets, it’s easy to get frustrated: there’s zero feedback and your emails are usually sent to the spam folder.

There are a lot of factors that influence the success of your cold emails. Arguably the most important is the subject line. It directly influences the open rate, click-through rate, as well as conversion. That’s why you must ensure your subject lines are of high quality. 🥇

In this article, we’ll cover:

  • The role subject lines play in your cold email outreach
  • 4+ best practice examples that are backed by data

Ready? Let’s get started. 👇

Role of Subject Lines in Your Cold Email Campaigns

Subject lines play an important role in any email campaign, warm or cold. They’re the first impression of your emails; it’s the first thing your targets see of them. When they open up their inbox, they judge what you’ve sent them based on the subject line you’ve written.

Subject lines are more essential for cold email, simply due to the impersonal nature of emailing strangers. You must also consider that the people you’re targeting aren’t on your email list. This means that, when targeting US citizens, the CAN-SPAM Act is especially important. ⚠️

If you didn’t know, the CAN-SPAM Act is a law that governs the rules surrounding commercial email, especially bulk emailing. Regarding email subject lines, the law specifically states:

Don’t use deceptive subject lines. The subject line must accurately reflect the content of the message.

Even though The CAN-SPAM Act is for both warm and cold emailing, it’s probably more significant for cold. Most email marketing tools for warm emailing have safeguards in place to warn you of these types of mistakes, but cold email platforms typically don’t. This is something to seriously consider whenever you send prospective sales/marketing emails to targeted strangers.

Put simply: It is important to have a list of valid email addresses for your cold email outreach and the goal of a subject line is for it to get the target/reader to open the email. This is emphasized in importance with cold emailing.

4+ Subject Line Best Practices (Backed by Science)

Below, you’ll find 4+ different best practice strategies you can use to improve the subject lines of your cold emails. Each will include some real, visual examples; that’ll help you understand how to effectively implement them.

NOTE: You won’t be able to use all of these together at once. Some of them are appropriate for certain emails and contexts, where others are not. Consider all of the strategies outlined below as tools in your toolbelt.

1. Personalize Your Email Subject Lines

Did you know that emails with personalized subject lines have a 22.2% greater chance of being opened? This isn’t surprising in the least: personalizing your email subject lines makes them far more effective; warm or cold.

But why is this? 🤔

People love to hear or read their own names, or at least something personal to them. It was Dale Carnegie — author of How to Win Friends and Influence People — who once said:

A person’s name is to that person, the sweetest, most important sound in any language.

Does it need any more explanation than that? If you received two emails with identical subject lines, except for using your name, which one would you open first? Exactly: personalization works because… it’s personal — and so is email messaging.

So, how do you personalize your email subject lines? There are several different methods you could try, including the most obvious: simply using their name. Here’s a list of ideas you can potentially use:

  • Use their first name or full name
  • Use the name of the company they work for
  • Use their job title

How personal you can get will be limited to the data you have on them. A good contact database/list will help you find relevant information.

To personalize a step further, you could search them up on LinkedIn. It could tell you that they attended a conference, event, or workshop. It could also tell you what articles they’ve read, liked, or even written. If they’ve got social media profiles, check them out.

If implemented correctly, here’s how it could look:

2. Keep Your Email Subject Lines Short

Another tactic you can use to supercharge your cold email subject lines is to simply keep them short… no, really: that’s it. Sometimes less is more, and often this is the case when it comes to subject lines for emails.

An email subject line — warm or cold — that’s too long will fail to catch your intended target’s attention. This is primarily because of 2 reasons:

  • They often get cut off past a certain character length
  • They’re long winded and unfocused

On the other hand, shorter subject lines are specific, focused on a particular point or intended goal. They also never get cut off, which is a huge plus. 👌

So, how short exactly, is ideal? After all, it’s a rather vague term: what’s too long, too short, and just right? Well, there’s not an exact number; all subject titles are different: they’re promoting a unique email about a specific topic.

Too long is anything that gets cut off. What’s the point if they can’t see it? Too short is one that doesn’t get the message off you intended. Why even send the email if you’re not effectively telling them what it’s about?

For what it’s worth, there was a study done on email subject line length and open rates. These were the results:

  • 0-5 words = 16% open rate
  • 6-10 words = 21% open rate
  • 11-15 words = 14% open rate
  • 16-20 words = 12% open rate
  • 21-25 words = 9% open rate

6-10 words length is the winner; I wouldn’t read too much into it, though. As stated before: each email is unique and requires a unique subject line. 0-15 words length will cover just about everything, but make sure to see if the subject line cuts off. Send it to yourself to check this out.

NOTE: Also consider that the character length, not just the word length, is important. This is what determines the visual length of a subject line in an inbox, and if it gets cut off. Screen size and browser zoom can influence this. 🔍

If done correctly, here’s how it could look:

If done incorrectly, here’s how it could look:

3. Use Urgency in Your Email Subject Lines

Another strategy you can use to improve your cold email subject lines is to add some urgency. This is when you add something like ‘limited supplies,’ or ‘while stocks last.’

What this does is tap into a psychological phenomenon known as FOMO: the fear of missing out. People don’t like it when they let an opportunity pass them by; nobody wants to be the odd one out. In fact, according to research, nearly 70% of millennials state they experience FOMO. 😧

By putting some urgency in your cold email subject lines, you’re forcing them into action. Incentivizing them to click and open. The research backs this up: a report found urgency-laced subject lines could increase email open rate by 22%.

However, make sure you don’t go overboard. If too many of your emails use urgency, it kind of defeats itself. Think of urgency as a curveball you can throw now and again to catch them off guard. For cold emailing, though, you probably won’t have this problem.

Here are some real-life examples of subject lines using the power of urgency:

4. Use Social Proof in Your Email Subject Lines

Adding social proof to your cold email subject lines is another psychological trick you can use. Much like the urgency tactic, social proof plays mind games with your intended targets. This is when you mention something that socially validates your brand.

Examples include:

  • Referencing how many customers you have
  • Referencing testimonials
  • Referencing case studies
  • Referencing celebrity/authority/credibility endorsements

It works because people are influenced by what others do, say, and think. We naturally try to uncover whether something is credible or not: social proof helps us do so. When your cold email target sees your subject line mentioning your massive customer base, they’re impressed. 😲

Here is a real-life example: this was an email promoting a video case study.

Here’s another one: an email promoting a free guide from an SEO authority figure.

Here’s an email about another case study.

And lastly, here’s an email from Adam Enfroy that uses both urgency and social proof for his course on how to start a blog.


The subject line of an email, cold or hot, can make or break it: whether it’s successful or not. It directly influences the open rate, click-through rate, and conversion as well.

Cold email outreach is not an easy endeavor. The number of emails sent that get opened is typically quite low. Most don’t even reach the inbox: they end up in the spam folder. Others land in the “Promotions” or “Other” folder. 📂

However, with the right subject line, you can significantly improve your odds. Consider utilizing the information and best practice examples outlined in this article; we hope you find it of value.

Got any questions? Don’t hesitate to leave us a comment or hit us up on the chat on our website.

A little about Will:
Will Cannon is a seasoned email marketer and founded UpLead, a B2B lead generation software. He knows a thing (or two) about great cold emails and loves to share his knowledge.

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