How to Write Email Subject Lines That Boost Open Rates
Published on 31.12.2025 by Chizoba T
One of the most essential elements of an email is the subject line, as it determines whether a reader opens the email, ignores it, or sends it to the spam folder. The subject line is a one-line summary of the email content that appears in the inbox.
A good email subject line should begin by grabbing the user’s attention and should be a key part of building an email marketing sales funnel that converts. It should be descriptive and personal, providing the reader with a reason to open the email. In this blog, we will explore why subject lines matter and discuss best practices for writing an effective email subject line.
Why You Need a Good Email Subject Line
A Zippie email research study found that the subject line drove 47% of email opens. Another study found that 69% of email users reported emails as spam based on the subject line. That means the subject line makes or breaks an email marketing campaign.
When you use an outstanding email subject line, you can increase the open rate and, in turn, the click-through rate and conversion rate. All in all, an email’s subject line matters for several reasons, such as:
- Attention-grabbing. When you send out an email, the first thing that people see is the subject line. This is what determines if your email will effectively grab people’s attention.
- Expectation setting. The first thing that people look at to know what to expect from an email is the subject line. When you use a well-crafted subject line, email users can understand what to expect.
- Bypass spam filter. Spam emails are one of the biggest challenges in email marketing. Top email service providers have identified certain words that serve as triggers for detecting spam. That means that when you use the wrong trigger words in your email marketing subject lines, your emails will be marked as spam.
- Increase the open rate. As noted earlier, when you use the right subject line, you can increase the likelihood that recipients will open your emails. This is particularly important in the email marketing campaign, where the open rate is one of the factors affecting its success.
- Encourage engagement. Another factor that affects the open rate of an email is the subject line. By using a catchy subject line, you can encourage the recipients to read more or take a desired action.
Therefore, the subject line will provide users with their first impression of what to expect from the email.
Tips For Creating an Email Subject Line
We have seen the benefits of having an outstanding subject line. Now, let us look at tips for making your email subject lines stand out:
Leverage Fear of Missing Out (FOMO)
A timeless social media growth strategy in any campaign is to stir people’s emotions. One of these is to use FOMO to increase conversion, where you create the impression that people who don't act quickly will miss out. A good idea would be to use email subject lines that evoke emotion, such as urgent, limited, critical, alert, etc. These words can help to increase your email open rate. Some examples of such subject lines are:
- You are missing out on our limited offer.
- One day remaining to expire on this offer.
- Your free start pack offer ends today.
- Earn a 30% discount today only.
Catchy Email Subject Lines
Catchy email subject lines are great for generating excitement and encouraging people to open emails. These subject lines can take different formats, such as an attention-grabbing subject line, a confident or controversial topic, or a conversation. You can provide users with a lead magnet or any other helpful resource.
Examples of catchy subject lines are:
- This method grew my email list 10 times in one month.
- These email list ideas will blow your mind.
- You won’t believe how these celebrities look after ending their careers.
Induce Curiosity in Your Subject Line
Humans don’t have to be left hanging and will seek closure if complete information isn’t provided. The desire for closure is another emotional trigger you can use to create curiosity in the subject line. You can, therefore, leave some information in your subject line to encourage viewers to open. To increase the curiosity of readers, use an ask, promise something intriguing, or use an unusual or strange sentence.
Examples of such subject lines include:
- Don’t try to open this email.
- Last chance to learn about this mystery email.
- This is the most disgusting video you will see in 2025.
- Italy is looking for these professionals with 6-figure salaries.
Add Humor to Your Email Subject Lines
There is no doubt that in a highly stressful world, humor sells. This is why something funny resonates with your target audience. However, remember that it will take extra effort to be humorous and creative. But when it resonates with your target audience, it will increase the open rate.
Examples of humorous subject lines can include:
- Deals that will make you proud (unlike our niece Stacy).
- Your wish.
- Avoid these people this Christmas.
- New vacation to the moon.
Appeals to Vanity
Every person has a bit of vanity that feels the desire to be liked, revered, or accepted. This is why subject lines with some vanity are effective at getting people to open their emails. To use vanity in your emails, you can promise your users something that makes their subscribers feel better. Alternatively, you can create a fear of getting ashamed.
Examples of email subject lines leveraging the fear of getting ashamed are:
- Are you the only one wearing last year’s fashion?
- These fashion items will leave heads turning.
- Women swear this lotion makes them 10 years younger.
Greedy Email Subject lines
Nobody wants to be considered greedy. When a great deal comes along, few people have the willpower to pass it up, even when they don’t really need it. To leverage the emotion of greed, you can use words like "special offers," "sales," and "discounts" in your email subject line. However, be careful with using massive discounts, as these may affect the open rate, probably because they look unrealistic.
All in all, when you mention a discount in the subject line, you are likely to see a higher click-through rate. Here are new examples of discount offers you can make:
- Flash sale.
- Buy one, get two.
- Gift for all your purchases.
- Get yourself priority access.
You can also use power words to increase engagement.
In Conclusion
The subject line gives an email reader their first impression of what to expect from your email. If your email subject line is bland, it will affect the click-through rate. By using these tips, you can increase your email open rate.