How To Write Better Email Subject Lines (Best Practice Guide)

Looking to write better subject lines that get your emails opened and read? You’re in the right place.

When sending marketing emails, the subject line makes the first impression on your recipients. A great subject line can be the difference between an email that gets opened and one that gets ignored.

In this post, we guide you on the best practices for email subject lines that drive engagement and boost your email marketing ROI.

Importance of email subject lines

Email subject lines are just as important as the email content.

They play a crucial role in email marketing success, and that’s why you need to put more effort into crafting them.

Here’s why your email subject lines matter:

They impact engagement: Email subject lines directly impact the most important metric, the email open rate. This, in turn, affects other engagement metrics such as click-through rates, response rates, conversions, and overall campaign performance.
Creates the first impression Your subject line creates the first impression with your recipients. A strong subject line grabs attention, sparks curiosity, and encourages recipients to open your email.
Affects deliverability: Spammy or misleading subject lines can land your emails in the junk folder.

What makes a good email subject line?

A good subject line generally has the following characteristics:

Short and concise: Typically under 50 characters to display fully on mobile devices.
Is personalized: Has the recipient’s name or other tailored details on it.
Is action-oriented (Has a CTA): Uses verbs that encourage action (e.g., Grab, Register)
Conveys a sense of urgency and scarcity: e.g. “Only a Few Spots Left – Register Now”.
Sparks curiosity: Create a little mystery that sparks interest (e.g., “You Won’t Believe This Offer”).

Best practice for email subject lines

Crafting compelling email subject lines is a skill that every email marketer needs to master. It’s one fail-proof way to improve email open rates and boost engagement.

Here are some of the best practices for writing effective email subject lines:

Personalize the subject line

One of the surest ways to make your email subject lines perform better is to personalize them.

Recent marketing reports show that personalizing subject lines increases open rates by 50%.

People are more likely to open an email if they feel it was written specifically for them rather than for a group of people.

How do you personalize subject lines effectively?

Use the recipient’s first name (e.g., “Sarah, Here’s a Special Offer Just for You”).
Reference their past interactions, such as past purchases or browsing history (e.g., “Still Thinking About That Jacket, Alex?”).
Segment your audience based on preferences, behaviour, or demographics (age groups and gender) so you can send relevant messages to relevant groups.

Example:

Personalization goes a long way in creating a stronger connection with the recipient, increasing their chances of opening and engaging with your emails.

Write relevant email subject lines

The subject line is not just a place to grab attention, it’s also where you let the recipient know what the email is about.

Always write subject lines that are highly relevant and communicate the contents of the email. A relevant subject line ensures that people know what to expect when they open your email.

If your email recipients find it misleading or too vague, they might ignore it or, worse, mark the email as spam.

How do you ensure your subject line is relevant?

Ensure it aligns with the content in the email body
Highlight the main benefit the recipient will get from opening the email. Make them know ‘What’s In It For Me (WIIFM).’
Avoid misleading or clickbait-style phrases that may damage trust (e.g “You Won’t Believe This!”)

When you set clear expectations in the subject line, you increase the chances of engagement and reduce unsubscribes.

Keep it short and sweet

The best-performing email subject lines are always short and straight to the point.

With people receiving dozens of emails daily, long subject lines can easily get ignored. Besides, too wordy subject lines may be cut off, especially on mobile devices.

Aim to write short subject lines that are not more than 50 characters and between 6-8 words.

Remember to make it stand out by placing the most important words at the beginning.

Examples:

“Final Hours: 50% Off Sale Ends Tonight.”

This subject line is short and sweet, likely to be opened.

“This Is Your Last Chance to Take Advantage of Our Limited-Time 50% Discount Before It’s Gone Forever.”

This is too long and overwhelming, likely to be ignored.

Include a call-to-action (CTA)

Effective email subject lines have powerful action words that encourage recipients to take action.

Whether you want them to read an article, shop a sale, download a resource or register for an event, a clear Call-to-Action (CTA) can significantly boost engagement.

Action-oriented words help to highlight what the recipient will benefit from opening the email.

Examples of CTAs that make your subject lines perform better include:

Get
Claim
Shop
Join
Grab
Check
Register
Download

These action words create a sense of excitement or exclusivity to entice your recipients to take action.

Create a sense of urgency

People are more likely to take immediate action if they feel like they might miss out on something valuable.

Use your subject lines as an opportunity to create a sense of urgency to encourage quick decision-making.

For instance, use time-sensitive words like “Hurry,” “Limited Time,” “Final Chance,” or “Offer Ends Tonight.”

Example:

Instead of saying “Big Sale Happening Now,” create a sense of urgency by saying “Only 2 Hours Left! Claim Your 30% Discount Now.”

This will help to prevent recipients from postponing their response and increase conversions.

However, be careful not to use urgency too often, as it can lose its impact over time. Also ensure that whenever you use it, it’s authentic to maintain trust with your audience.

Make it sound exclusive

Another effective way to improve your subject lines is to make people feel special.

Make the content sound exclusive so the recipient can feel like they’re getting access to something others aren’t.

You can do this by using words like:

Exclusive
Private invite
For VIPs only
Members-only

You can then offer early access to new products, sales, special discounts, or other exclusive content.

When your subject line suggests limited access or VIP treatment, recipients become curious and are more likely to open the email.

Example:

“Exclusive for You: 20% Off Before Everyone Else!”

Use numbers

Numbers make subject lines more specific, digestible, and eye-catching.

They set clear expectations for the value the reader will get when they open the email. Numbers also make subject lines stand out visually among many text-based subject lines.

For instance, instead of vaguely saying ‘How to Save Money on Travel,’ a more compelling subject line would say, ‘5 Ways to Save Money on Your Next Trip.”

Here’s a live example from my inbox:

Using numbers makes your content seem structured and easy to consume (e.g., listicles). They make great subject lines that are more compelling for recipients to click.

Add preview text

While not part of the subject line, preview texts (or preheader text) complement subject lines and increase email open rates.

Preview text is the short snippet of text that appears next to or below the subject line in inboxes.

This extra space often provides an opportunity to expand on the subject line and entice recipients to open the email.

Here’s how to add an effective preview text:

Expand on the subject line without repeating it
Provide a clear benefit or tease what’s inside the email
Keep it short and engaging, ideally under 100 characters

Subject Line: “Your VIP Discount Expires Tonight!”
Preview Text: “Get 30% off before midnight—this deal won’t be back soon!”

Start adding preview text strategically to motivate readers to open your email and increase open rates.

Ask a compelling question

Some of the best-performing email subject lines are those that ask compelling questions.

Questions naturally spark curiosity and encourage recipients to think about the answer. This makes them more likely to open the email.

When using question-based subject lines, always ensure they are relevant, engaging, and thought-provoking.

Use open-ended questions that spark curiosity or address a common pain point or challenge.

Here’s an example of