Consumers’ inboxes today are overflowing with emails from brands—and most people aren’t keen to open these messages. According to a Gartner study, only 23.9% of sales emails get opened.
Your email subject line is more important than any other part of your sales email because it’s the first thing your potential customers see, and it’s the deciding factor on whether or not your email gets opened. If you don’t grab a reader's attention in your subject line, there's a good chance they won’t even open your message.
The key to writing compelling sales email subject lines? Knowing who your audience is, what they want, and how to motivate them to buy your product. Combine that knowledge with a bit of creativity to craft a subject line that grabs your customers’ attention—this combination will compel them to open the email.
Understand what makes good sales email subject lines
There’s a lot of research on what makes for successful email subject lines, including OutboundEngine’s list of the top-performing email subject lines, which highlights how what works varies widely based on context.
With that said, most successful email subject lines have a few factors in common:
1. They’re short
According to Marketo, 41 characters—or seven words—is the optimal engagement performance range for an email subject line, meaning they have the most open rates and the most click rates. This is the optimal range as far as performance, but it’s hard to get all the details you need to get your point across creatively in the sales email subject line, so the character range is flexible. In the example below, we have an email subject line with seven words.
This 41 character limit used for optimal engagement performance is approximately 10 characters shorter than the average length of email subject lines, according to Marketo.
2. They include a number
Numbers in email subject lines imply that the email writer is an expert and is giving advice in their email, enticing people to read their emails. For example:
3. They’re formatted like a question
If you state your email subject line like a question, you’ll spark the recipient’s curiosity. If they want to know the answer to the question, they’ll likely open your message.
4. They don’t include emojis
It might seem like emojis would help your subject line. However, a survey conducted by Search Engine Journal (SEJ) found that subject lines with no emojis had a higher open rate than those with emojis. The survey participants typically used the words “dull” and “boring” to describe emails with emojis in the subject line.
Answer these key questions
Before you write a word, you first need to hone in on the basics:
- What product are you selling?
- Who are you selling to?
- What will motivate your audience to buy your product?
Answering these three questions will determine how you tailor your sales email subject line to target your audience. Some of these answers may seem obvious but knowing who your audience is can be hard to pinpoint. Some people may say that it’s everyone, while others have a very niche audience. A broad audience becomes problematic because it’s tough to convince everyone to buy your product while having a niche audience makes it easy to find what motivates them and tailor your product and your email subject line to that niche audience. Therefore, try to get as exact as to who your audience may be.
5. They answer What product are you selling?
Say you own an online health food store, and you’re trying to sell a nut-free/gluten-free nutritional bar. You’ll want to clearly identify your product in the subject line, so your audience is clear about the email’s focus.
6. They answer Who are you selling to?
Your key demographic for this kind of product will most likely be health buffs or parents looking for a healthy snack alternative for their children to eat. Instead of sending the same email to all recipients, you can adjust the subject line for each audience to make sure it’s relevant for each group.
For a fitness health buff, you want an email subject line that directly talks to them in a strong tone that would target an athlete. To do that, put in an exclamation mark to show that they should get pumped about your product.
Example of an email subject line for a fitness health buff
For a parent looking for a healthy alternative snack, the tailored tone should be caring and fun. So you’ll likely want to avoid exclamation marks. Instead, use words that they would probably use. In our example below, we used the word yummy.
Example of an email subject line for a parent
7. They answer What will motivate your audience to buy your product?
The tailored subject lines above are a good start—but you can tweak the language even further to speak to each audience’s needs and encourage them to make a purchase.
For the health buff group, you might focus on how much protein the bar has and that it’s low-calorie.
Example of an email subject line for a fitness health buff
But if you're targeting parents looking for healthy snack alternatives, you'll want to focus on how delicious it is and how it provides all the nutritional content a parent and their child could need.
Example of an email subject line for a parent looking for a healthy alternative snack
Each email subject line improves with each step taken. For example, when you include your product, change your tone based on your audience, and put in target words to motivate your audience, this covers all your bases and makes for an email subject line that is strong and persuasive.
Brainstorm subject line ideas using Copy.ai
When it comes to writing, most of us never hit on our best ideas the first time around. Start by brainstorming a large set of ideas, so you can eventually find your rockstar subject line.
Aim for 8 to 10 subject line possibilities to start, and don’t worry if they’re good. Just get all of your ideas down on the page. We all have to start somewhere!
For inspiration, start with your email inbox, looking at which subject lines successfully caught YOUR eye. Which emails subject lines did you open the first time around?
If you want some help jumpstarting your creativity, try using Copy.ai’s catchy email subject line tool. Put in all the details you know and want to include in your email subject line, and our AI-powered software generates a list of subject line suggestions of different lengths, styles, and content. Save the ones you like, combine a few phrases, and generate even more. The possibilities are endless.
Let’s use our health food shop example from above. In Copy.ai, you would simply plug in your nutrition bar product and a description of the item. The more details you give, the more the AI will have to work with. In return, you’ll get more tailored results.
The tool generates tons of sales email subject lines.
You might not love every option, but the tool is a good starting point and should help you get the thinking process flowing. From there, you can put more details in the email subject line and tailor it to sound more like what you’re looking for.
Refine and polish your sales email subject line
You’ve got a list of brainstormed subject lines. Now, it’s time to tweak this text to make sure it’s not only informative but also attention-grabbing. Here are a few tips to make your sales email subject lines even more compelling.
8. They are Personalized
Personalization is a nice little treat that makes your customers feel like you took the time to curate your message just for them. But make no mistake—personalization is no longer a nice-to-have element. It’s an expectation by today’s consumers.
According to Statista,90% of U.S. consumers find marketing contentthat is not personalized annoying.
There are all sorts of ways to personalize a sales email subject line, like using your recipient's name or sending them an email for their birthday.
9. They Communicate urgency
The fear of missing out (FOMO) is real, and it has a powerful effect on your marketing. Apply it to your emails by emphasizing a deadline in your subject lines. You might highlight a deal or discount that will expire soon. This deadline should make readers feel like they need to open it and not miss out.
Or, you could share how there is a limited quantity of your product and explain that the reader needs to act quickly before the item sells out.
10. They Avoid Spammy words
In March 2021, 45.1 percent of the emails sent were spam. That is, nearly half of all emails were either spam or were blocked. Even the messages that don’t get sorted into spam are still subject to discerning recipients fed up with too many promotional emails.
Keep your email subject line from sounding too sales-y and spammy by avoiding trigger words—“free,” “money,” “help,” and “reminder” are just a few examples. Email systems will recognize these words as spam-related and likely filter the message straight to the junk or spam folder.
Unfortunately, there are a lot of these words, even symbols, that you can’t use. Check out a thorough list of these terms at Yesware Blog.
11. They are professional
Grammar errors are a guaranteed way to seem unprofessional. Make a strong first impression by running your subject line (and message) through spell check.
Go one step further by using a tool like Grammarly. Grammarly is a cross-platform app that you can download onto your devices to check your spelling, grammar, punctuation, basically, any literary mistakes. In general, it's a good rule of thumb to check any messaging sent to potential customers with Grammarly.
If you want your subject line to look professional, don’t use all capital letters. A study by Boomerang found that of 300,000 emails, a subject line in all caps was 30 percent less likely to get a response. People tend to think using all caps is unprofessional.
For more unprofessional habits to avoid, check out this list of mistakes from Insider.
A/B test your sales email subject line
Don’t blindly guess which sales email subject line works best. Test variations using A/B testing, also known as split testing.
With A/B testing, you send a few distinct email subject lines to small sample groups before sending them to your entire audience. Then, you can compare the results and send the best-performing line to your complete list of subscribers.
A/B testing is pretty simple in nature, but the little details can give you skewed results, so you’ll want to be consistent in your testing each time.
- Download an A/B testing tool. There are several tools you can use to do A/B testing, such as Constant Contact.
- Upload your email contact list.
- Create two or more sales email subject lines that you would like to use. Just one element should be changed to have a controlling factor.
- Split your testing population contact list into equal numbers based on how many subject lines you’ll be testing. For example, if you have two subject lines you’ll be testing, split your test population contacts in half. If you have three, then in thirds, and so on and so forth.
- Send the first subject line to the first divided portion of your contact list. Your second subject line gets sent to an equal number of contacts, not the duplicate contacts you used for your first subject line.
- After a set amount of time (be sure to use consistent timing for each subject line), the email subject line that performs better is the one you’ll use going forward. That email subject line gets sent to the remaining contacts in your list that were not part of the A/B testing population.
A/B testing is a win-win for both your brand and your recipients. You’re likely to see higher open rates, and your audience is more likely to find the email relevant.
Send off your email and check your open rates
Think of each email as a learning opportunity. By sending off and checking your open rates, you can improve your sales email subject lines in the future. There are a few ways to do this.
- Use an email tracking tool, such as Klaviyo, that shows you who has read, clicked on your email, how many times they’ve done it, and when.
- Put a hyperlink in your email and track how many people click on your link.
- Request a return receipt—a notification that confirms whether or not the recipient received and opened your email. Most major emails sites, like Gmail and Outlook, offer this feature.
By tracking your open rates, you can see what your audience responds to and implement those factors into your future sales email subject lines.
Keep practicing your sales email subject line writing
Sales email subject line writing is an art that takes practice. Use this guide as a starting point, and keep building your writing skills by brainstorming and testing ideas. This will result in higher open rates as you continue to practice.
Once you become comfortable with your sales email subject lines, you can start to branch out and apply your skills to other areas of your creative marketing. Copy.ai’s AI-powered tools can help with much more than just sales email subject lines, like generating blog ideas, Instagram captions, Facebook ads, product descriptions, LinkedIn ads, and much more. Get started today for free!