Email Marketing

Email Subject Line Best Practices: 9 Things You Should Be Doing

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Email subject lines are one of the most critical elements of any email marketing campaign. They are the first thing subscribers see upon receiving an email and, according to 47 percent of subscribers, they play a crucial role in determining whether or not an email gets opened and read.

As a marketer, it’s essential to understand how to write a good subject line––one that will engage your audience and drive conversions. Below, we’ll list our top nine email subject line best practices.

Email subject line best practices

Email marketing helps businesses stay in touch with customers, promote their products, and drive sales. But with so many emails being sent every day, it’s important to make sure that yours stand out in a recipient’s inbox. Here’s how…

Keep it short

There are many conflicting studies around email subject line length. And, truthfully, there have been wildly successful subject lines of all lengths. But best practice states that, for many recipients (especially those on mobile devices), the shorter the better. Why?

Different devices have different display capabilities––A typical desktop inbox displays about 60 characters of an email’s subject line, while mobile devices show just 25-30 characters. Additionally, many email clients tend to truncate subject lines that are too long, making it harder for recipients to understand the purpose of the email at a glance.

Long story short (no pun intended), concise subject lines are more likely to catch a subscriber’s attention, as they stand out more in a crowded inbox. That said, we recommend no more than 9 words and around 60 characters.

Use personalization

Personalizing your subject lines can also be a powerful way to increase engagement and conversions. This means using the recipient’s name and any other relevant information in the subject line. For example, subject lines like “Welcome back, [First Name]” are more engaging than subject lines with no personalization at all.

Avoid a no-reply email address

Regulatory bodies like CAN-SPAM decree that businesses should never have a no-reply email address. Not only is it off-putting to subscribers (it doesn’t allow for two-way conversations) but it can have a serious impact on an email’s deliverability (more likely to be marked as SPAM).

It’s also non-compliant––per the CAN-SPAM and GDPR, recipients must be able to easily request information about the data collected about them and have a clear option to opt out with a reply email.

A/B test

Another best practice is to test different subject lines to see which ones perform best. This means sending different variations of your subject line to a small group of recipients and then comparing the open and click-through rates to see which subject line is the most effective. This should be a regular part of your email marketing campaign reporting as it will help you optimize your subject lines over time and improve overall campaign performance.

Avoid using ALL CAPS

Using all caps or exclamation points in your subject line can harm your sender reputation. This is because these types of punctuation are often associated with spam emails. Instead, use a more natural and conversational tone in your subject lines, which will help build rapport with your audience and increase the chances of them opening and engaging with your emails.

Don’t be clickbait-y

Avoid using misleading subject lines, making unrealistic promises, or otherwise making use of spam words as it can damage your reputation, erode trust with your audience, and lead to lower engagement and conversions. For example, using a subject line like “You won’t believe what we’re offering,” while enticing, is likely to do more harm than good.

Segment your email list

Segmenting your audience allows you to tailor a subject line to the specific interests and needs of each group. This can increase the chances that the recipients will open and engage with the email, as the subject line will be more relevant to them. It also helps you avoid sending irrelevant or uninteresting content to certain groups, which will decrease the chances that they will mark the email as spam or unsubscribe from future communications. Overall, segmenting your audience should be done with the goal to create more targeted and effective communication that resonates with your audience.

Use emojis (sparingly)

Emojis can be a fun and effective way to make your subject lines more engaging and increase open rates, but it’s important to use them in a way that’s appropriate for your audience and aligns with your brand and messaging.

Keep it simple by using only one or two emojis that effectively convey the main message of the email. Secondly, ensure that the emojis are relevant to the content of the email and add meaning to the subject line. Thirdly, consider the cultural and demographic makeup of your audience and make sure that the emojis you use will be understood and well-received by them. Testing different subject lines with emojis can also help to find out what works best for your audience. Finally, it’s important to note that emojis are not supported by all email clients, so make sure you have a text fallback for the subject line for the email clients that don’t support it.

Use numbers

Like emojis, numbers are another great way to catch a subscriber’s eye but, again, you must be strategic in how you implement them. First, be specific with the numbers you use. Instead of using vague terms like “lots” or “many,” use specific numbers that give the recipient a clear idea of what to expect in the email. For example, “50 percent off sale” is more specific and compelling than “big sale.”

Second, use numbers that are relevant to the content of the email. If the email is promoting a sale, the number should be related to the discount or the number of items on sale. If the email is sharing statistics or data, the numbers should be relevant to the information being shared.

Third, consider the formatting of the numbers. Use numerals rather than spelling out the number, as this is more eye-catching and easy to read. Also, consider using bold or a different font for the numbers to make them stand out even more.

Finally, use numbers in a way that creates a sense of urgency. For example, “Limited time offer: Only 12 hours left” or “Last chance: Only 5 spots left.”

Types of email subject lines

Beyond what goes into an email subject line, you might be wondering what approach makes the most sense. While it depends on your overall intent, the below are all great starting points…


Tried and true, these types of “how to” email subject lines should make it clear to your readers that they will learn something new by opening your email. Be specific and clear––the subject line should accurately reflect the content of the email, and let the reader know exactly what they will learn. Using action words such as “learn,” “discover,” or “improve” also goes a long way.

Example: “Learn how to Organize your Inbox in 10 Simple Steps”


As always, we recommend adding a personalized touch to your emails whenever you can. That doesn’t just stop at adding the recipient’s name in the subject line, though. You can personalize the subject line according to the recipient’s past interactions: If you have a history of interactions with the recipient, you can use the past interactions as a reference to make the subject line more relevant to them.

Example: “John, we have a special offer for you, as a valued customer”


Curiosity is a strong emotion that often leads to action so why not use it to your advantage? Asking a compelling question in the subject line can make the reader curious about the answer and increase the chances of the email being opened.

Other ways to evoke curiosity are:

  • Teasers: Give a glimpse of what’s inside the email without giving away too much information. This can make the reader curious to know more and increase the chances of the email being opened.
  • Surprising or intriguing statements: Make a statement that is surprising or intriguing, this will make the reader curious to know more and increase the chances of the email being opened.
  • Scarcity: Use scarcity to create a sense of urgency and make the reader curious about what the email contains.
  • Storytelling: Create a story in your subject line that makes the reader curious about what happens next.

Example: “Have you ever wondered how to double your sales in a week? “


Who doesn’t like to feel included? Tapping into your recipient’s sense of FOMO is another great way to compel them to action. Be sure to explicitly name the event in the subject line so that the recipient knows immediately what the email is about. Remember to use a sense of urgency, too. If the event is happening soon or there are limited spots, use language that creates a sense of urgency to encourage the recipient to register. If there’s room, mention the benefits of attending the event in the subject line to make it more appealing to the recipient.

Example: “Don’t miss out on our upcoming members-only sale: 75% off all bestsellers. Sign up now.”


Some emails are automated but that doesn’t mean they need to sound stale and robotic. Get specific! For example, if you are sending out cart abandonment emails, use language that creates a sense of urgency to encourage the recipient to complete their purchase. Take it a step further by mentioning the item that was left in the cart in the subject line to remind the recipient of their interest. You may even go as far as offering a special deal, promotion, or discount code, to entice the recipient to complete their purchase.

Example: “You still have [product name] left in your cart! Stock is limited so act now.”

Write the perfect email subject line

Suffice it to say, crafting effective email subject lines is essential for any marketer. By following the subject line tips outlined above, you can increase engagement and conversions, build trust with your audience, and ultimately drive more sales.

That being said, some basic mechanics drive success when it comes to writing the perfect email subject line such as keeping subject lines concise, using action-oriented language, and conveying your purpose without the use of spam words.

Ready to take your email program to the next level (and stay a step ahead of hungry competitors)? Download Validity’s 2023 Email Marketing Benchmark report.