The Best Cold Email Subject Lines & How to Write Them

This post will teach you how to write cold email subject lines that get opened and a few examples to get your creative juices flowing.

Cleverly Team
Sep 30, 2021
12 min read


No matter how good the information contained in an email is, it will be useless if no one ever opens it. While it’s important to ensure the content of your email is compelling, it’s just as crucial to catch the reader's eye with a winning cold email subject line.

An email’s subject line is our one chance to pique the interest of the receiver and get them to click on that open button.

Read on to find out more about cold emailing and how to create the best subject lines to change your prospecting emails into genuine leads.

What Is a Cold Email?

Just like cold calling in days past, cold emailing involves reaching out to people who haven’t asked for information about a company’s products or services. Just like cold calling runs the risk of being ignored, so does cold emailing. The sender must find a way for their subject lines to stand out from the crowd or their email campaign may be a wasted effort.

There are various ways to make a subject line enticing. If it sounds personal or sparks interest, then the chances of the receiver opening the email increases. By the same token, if it sounds insincere or makes outlandish promises, the chances of success go down significantly.

Of course, even the best cold email subject lines will do a company little good if the email ends up in the spam folder before the recipient even gets a chance to look at it.

How To Keep Cold Emails Out of Spam Folders


If your email is sent to a prospective customer’s spam folder, your connection may never occur. Emails in spam folders are most often automatically deleted without ever being seen.  

Cold emails are sent by the thousands each day, so email service providers (ESPs) try to combat them to keep their users from being overwhelmed and frustrated by their presence. Many ESPs have developed software to recognize and filter out unsolicited — or "spam" — emails using proprietary algorithms and user input.

While this may be discouraging for many trying to bring value to potential customers, there’s still hope for cold emails. You just need to convince the spam filters that the email is legitimate. Below are a few ways to do just that.

Avoid Trigger Words and Phrases

Spam filters are designed to determine whether an email is legitimate or not, so avoiding the common red flags associated with spam is important. One of those characteristics is the use of overtly "salesy" words or phrases. Here are several examples:

  • Make $; Earn $/$$$ — your best bet is to stay away from dollar signs completely
  • Order; Order Now
  • Cash
  • Bonus
  • Cheap ‌
  • Free
  • Incredible Deal
  • Why Pay More?
  • Miracle ‌

Another good rule of thumb is not to promise things that cannot be delivered. Also, emails will often get flagged as spam if their subject lines start with greetings like “Hello” or “Dear” followed by a name or email address.

Avoid Excessive Punctuation Marks



Even one exclamation point or question mark in the subject line may get an email flagged as spam, but several or both of them in a row most certainly will.

Avoid All Caps

‌A subject line in all capital letters may attract the attention of the reader, but it may also prompt them to immediately mark the email as spam. Even if the reader does not flag the email, spam filters most likely will.  

Additionally, in the world of emails and texting, using all capital letters is perceived as yelling. Yelling at prospective customers is never a good thing, so this should be avoided in general.

‌Avoid Random Caps

‌‌This is a relatively new trigger. Since using all caps is not recommended, people began sending out emails with subject lines with a random mixture of upper- and lower-case letters. ThEy fReqUnelty LoOk sOMetHing lIKe THis and are very effective at attracting the reader's eye.

They’re also very effective at getting folks to hit the "Mark as Spam" button. It didn’t take the spam police long to see through this technique, and it should always be avoided.

Protect Your Company’s Reputation

If your company gets a reputation for sending out spam emails, there’s a greater likelihood that any future email campaigns will be immediately flagged as spam. This will lead to poor response rates on any subsequent mailings, regardless of content.

‌If an email campaign is sent out with solid email subject lines and the response numbers are still lagging, your IP address may have been blacklisted by the ESPs. You may not be notified of this action, but if you suspect this to be the case, there are sites that can help you confirm it. If you have been blacklisted, you may need to find another provider to keep your emails out of the spam folder.

Warm Up Their Inbox

What about those prospective customers wh‌o signed up to receive emails from you but no longer open them? Reinforcing the idea that your mail is not spam is a good first step, but you’ll likely need to do a bit more to re-engage their interest.

There are several tricks, known as “ warming the inbox,” that you can use to get those disinterested recipients back. These have shown success in boosting the open rate of email sent to “lost” customers:

  1. Give them something: Offer a reward or bonus for returning to the fold.
  2. Offer them a choice: Send out an informative email related to a subject the customer previously showed an interest in. In the body of the email, give the recipient a series of options about what they would like to learn more about in a future email. Now they know what to expect from the next email and will be more inclined to open it.
  3. Segment your contact list: By dividing your list into segments based on demographics you can send emails catered directly to each segment's interests.
  4. Do A/B testing: This will be discussed in greater detail below.

Create Informative, Relevant Content

While all the tactics above are a good way to avoid being recognized as spam, it’s always best to simply create an email that people want to receive. The email should be informative, relevant, and provide insight into why the goods or services being offered are an asset to the receiver.

What Makes a Subject Line Great?

The easy answer to this question: anything that gets the reader to open the email. Of course, we all know that the internet is not a one-size-fits-all kind of place. A subject line that makes one person giggle may seem ridiculous to another.

Here are a few ways to create a great prospecting email subject line that can appeal to a large audience:

  • Make it short: Be direct. The fewer words in an email subject line, the more likely the email gets read.
  • Use name recognition: Using your brand’s name or, better yet, an individual’s name followed by the brand name, e.g. "Maddie Whitestone from Brand X," makes the reader feel like they already know who the sender is.
  • Use the reader’s name: This is, of course, not always possible when sending mass emails, but when it’s doable, it increases the odds of the email being opened.
  • Don’t sound too good to be true: Very few people believe their life will change for the better in an instant. Don't promise your reader that opening an email will do that for them.  
  • Be humorous: Puns and other wordplay will amuse and raise interest.
  • Tell them what’s inside: Let the reader know that there’s valuable information to be had by opening the email.
  • Add a bit of mystery: Pique the reader's interest but leave enough mystery to make them want to learn more.
  • Ask a question: Be specific. Avoid general questions like, “Do you want to have a better life?” Instead, try to appeal to your audience by targeting their pain points.
  • Make it relevant: Get to know the type of people you’re emailing. Learn the social trends they follow and write subject lines that mean something to them.
  • Drop names: If you have a mutual contact with the recipient, include that name in the subject line to help break the ice.


‌Best Email Subject Line Checklist

‌Since your goal is to get people to open and read your emails, it’s helpful to have a checklist of best practices to create an effective subject line for cold emails. Here’s one to get you started:


  1. Is the reader going to be curious about what’s in the email?
  2. Is it clear what the email has to offer?
  3. Is the message geared towards the right demographic? (Example: Don’t try to sell hair styling products to bald men.)
  4. Is the message trendy and up-to-date?
  5. Is the message concise and easy to understand?
  6. Is there a sense of urgency or importance?
  7. Is the message personalized?
  8. Is the message believable?
  9. Have you avoided words that will trigger spam filters?
  10. Does the message have a positive vibe?


Preview Text Is Vital Too

‌Creating an effective subject line for an email campaign is important to its success but it’s not the only tool for improving open rates. Subject lines can only be so long, and it’s likely that more information might be needed to get a prospective customer to take the next step of reading the entire email.

This is where catchy and informative preview text is important. Preview text is the sentence that appears next to the subject line when an email is displayed. This little blurb gives the reader a chance to see more information about an email and hopefully piques their interest.  

Preview text should be used to support and enhance the information in the subject line. It can be used to highlight details of the offer, create a sense of urgency, increase intrigue, or bring a smile to the reader's face. Basically, anything that will boost the chances that they will click on the email to find out more.


Templates for Cold Email Subject Lines

Templates are a great way to get started on writing effective subject lines. They give you a basic framework to work from and build on. Below are several subject line templates to provide inspiration for creating your own.

  1. [Name], did you know...?
  2. [Name], are you looking for...?
  3. [Name] suggested I contact you.
  4. Can I help you, [name]?
  5. [Name], are you ready to...?
  6. X tips/ideas/suggestions about....
  7. [Name] told me you were looking for...
  8. Learn to …
  9. Remember your first/last......?
  10. Hi, [Name], good to meet you.
  11. Need ….? We can help.
  12. Can you help with...?
  13. Don’t worry, we can help with...


A/B Testing of Subject Lines

A/B testing is a simple way to determine the effectiveness of any email subject line. Before sending out an email, draft the body of the email, then come up with two distinct subject lines.

Send the emails to two small groups of prospective clients. One group should receive an email with subject line A. The other group should receive an email with subject line B. Once you send them out, you can track to see which of the groups has a higher ratio of opened and responded-to emails. This will help you determine what type of subject line is best for future emails.  

The Best Cold Email Subject Lines Are Worth the Work

Creating the perfect cold email subject line may seem like a daunting task, but the benefits of doing so far outweigh the hassle. An email's subject line is your introduction to the prospective client or customer. If it doesn’t gain their attention effectively, you may never get a chance to make a second impression.

If we take the time to get to know the interests and trends of our intended audience and use the tips mentioned in this article, we have a better chance of beginning a long-term, profitable relationship with the recipients of our emails.

Spending your time writing emails and crafting great subject lines is necessary to the success of many companies. It may be worth the money to outsource these tasks to professionals whose purpose is to help companies succeed through email campaigns.

Whether we tackle the issue of email subject lines ourselves or hire others to do it for us, it’s vital that things be done correctly. We may only get one shot at getting the recipient of our emails to learn about the great services or products we have to offer, so let's make sure we get it right.

If you’re not sure you and your team have enough time or specific skills to create the best cold email subject lines, contact Cleverly today. Cleverly knows the best ways to turn cold prospecting emails into valuable responses.

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