How To Write An Email Subject Line That Converts

With an estimated average ROI of 4400%, email marketing is now one of the most important aspects of any successful marketing strategy.

However, it is impossible to achieve the desired results if your correspondence is left unread in a recipient’s inbox.

Therefore, knowing how to write an email subject line is something that every marketer or business owner must learn.

Whether you’re about to start your first email marketing campaign or have spent hours agonizing over the prospect of writing a good subject line, this guide from the experts at Optimo AI will help you master the process.

The road to increased engagement and click-through rates begins here.

What is an email subject line?

An email subject line is a single line of text that a recipient sees when an email reaches their inbox.

It is a short and snappy piece of copy that has one purpose: to encourage users to open the email.

Email subject lines are designed to make a recipient want to learn more.

Therefore, it must provide succinct information while simultaneously raising a sense of intrigue.

With just under 350 billion emails sent per day, the email subject line is the first point of interaction and offers an opportunity to stand out from the crowd.

As with any marketing campaign, a great first impression could make or break your hopes of success.

Forbes states that 65% of emails are ignored and ineffective subject lines are the most common reasons.

Without a powerful email subject line, the content contained within the email will be rendered redundant.

So, while you may spend hours crafting the perfect email, a great subject line is often the most important feature.

In short; no email marketing campaign is complete without a great subject line.

What is an email subject line

How do email subject lines differ from content titles?

In many ways, email subject lines are similar to blog post titles and article titles.

They share several key objectives such as looking to engage the reader, generate a sense of curiosity, and paint a positive image of the brand.

However, email subject lines do differ from blog post titles for many reasons as detailed below:

  • Email subject lines should make the reader feel that the content is personalized to them whereas blog titles are impersonal and target a broad audience.
  • Readers discover blogs for themselves whereas emails are delivered directly to the user’s inbox, which can also influence the content styles of each.
  • A blog title often has to consider the SEO and meta description aspects, which is something an email subject line won’t necessarily do.
  • Blog titles are usually a little plain and simply inform readers what they will find. In comparison, an email subject line explains why the content is unmissable.
  • Email subject lines have to be brief – usually no more than 40 characters – white article titles have a little more flexibility.
  • Blogs often have the end goal of entertaining or educating the reader whereas emails often focus on promoting products and services.

It should also be noted that a blog title is the same for all readers.

Conversely, different email subject lines can be sent to different recipients, which is why 47% of marketers use ideas like A/B testing to try multiple options for greater optimization.

The importance of an engaging email subject line

The importance of an engaging email subject line

Catchy email subject lines play an integral role in the success of any marketing campaign.

As an email user yourself, you should have first-hand anecdotal evidence of this as you probably ignore dozens of emails each week due to poor subject lines.

The statistics support this further, highlighting the importance of an effective email subject line.

Some of the most telling insights are;

  • 64% of email recipients will decide whether they should open the email solely due to the quality of the subject line. So, the email open rates are almost exclusively determined by the effectiveness of this opening line.
  • Likewise, 33% of email recipients open emails because of catch email subject lines. This gives you a chance to capture a consumer’s attention even in situations where other ad ideas would have fallen flat.
  • Emails often provide the push needed to gain a sale. Cart abandonment emails, for example, can boost online sales by around 20%. An engaging email subject line is a key feature that makes this happen.
  • The average person is believed to receive around 100 emails per day. Even those that open their inbox several times per day won’t have enough time to read them all. A bad subject line will spell disaster.
  • Consumers now view promotional emails in the same way that they view spam emails. Subject lines are the most important feature for showing users that your content should not be ignored.

However, it should also be noted that the best subject lines must be followed by useful content.

This could mean including a great product description for an item they’ve checked out or other info that relates to their relationship with the brand.

Even newsletters should engage the reader from start to finish.

Not every email that a user opens will lead to a sale or gain the desired response.

Still, if they are made to feel that your content wastes their time, they will soon start to ignore your correspondences or send them directly to their spam folders.

Writing subject lines that set the tone and lead to quality content will yield the best ROIs.

How to write an email subject line

Some people argue that writing email subject lines is a science.

Others think it’s an artform.

Either way, there is no doubt that your business stands to reap huge rewards from mastering this handful of words.

But how can you do it?

Here’s all you need to know.

Know what your email is about

Within your jobs-to-be-done framework, you may want to write the subject line before or after you’ve composed the blog itself.

Either way, though, it’s important to know what the purpose of the email will be.

Otherwise, it’ll be very tough to create a powerful call-to-action.

Your CTA is crucial because you don’t only want your email to be seen.

You need the recipient to know what action should be taken.

Even if the CTA isn’t mentioned in the subject line itself, you should introduce the future CTA.

For example, if the goal is to sell a product, you’ll want to at least mention the product or deal within the subject line.

A thank you email or follow up email will be different from a sales pitch email.

Think about your brand positioning

An engaging subject line must suit your brand positioning.

Therefore, it’s important to know the difference between a catchy subject line and a funny email line.

You will have different email strands for different stages of the consumer’s interaction with the brand.

A welcome email, a sales promo email, an event invite email, and a customer feedback email will each have unique elements.

However, they should all link back to your brand positioning.

Otherwise, you may lose the authenticity needed to gain open rates and subsequent conversions.

Use AI

The landscape is constantly changing, but automated email subject line generators can help you stay ahead of the game.

The Optimo email subject line creator works particularly well and uses advanced A.I. to generate engaging subject lines that are built to convert.

To use the free tool, simply enter some details into the text box to let the AI tool know what your email is about.

This could include details about what your business does as well as the intended recipient and the purpose of the email.

Once you have clicked the button to generate the subject lines, the software will get to work.

Within seconds, you’ll be presented with multiple encapsulating titles that boast the clickability factor you crave.

Better still, you can use the generator time and time again until the perfect solution is found.

Use AI 

Utilize data


Data is your greatest ally.

For starters, you can monitor the progress of your email marketing campaigns to gain a better understanding of what works for your business.

However, you can also use general trends.

For example, adding the term ‘free’ or including the recipient’s name are just two examples that are shown to increase open rates.

Exclusivity is another feature that can work well.

Optimo takes this into account but it’s certainly worth noting when taking a manual route.

In most cases, though, AI is the way to go because it lets you act with confidence while also staying focused on your other jobs to do.

Tips for writing better email subject lines

The above information on how to write an effective email subject line should provide a solid foundation.

Nevertheless, the importance of this element means you cannot afford to rest on your laurels.

As the competition for customers gets increasingly fierce, maintaining high engagement levels is pivotal.

Here are 10 quick tips to help you write the best subject lines.

#1. Start with the keywords

Mobile internet usage has now overtaken desktop usage and millions of people open their inboxes on mobile devices.

As you do not know how many characters will be shown on a recipient’s device, it makes sense to start with the most vital information.

Besides, if the content doesn’t engage users from the first 2-3 words, they might not be willing to read to the end.

#2. Use FOMO to your advantage

You can make emails feel time sensitive to gently nudge prospective leads toward a buying decision.

A limited-time offer or mention that their cart is about to be emptied can work wonders.

When there isn’t a sense of urgency, recipients may decide to leave the process until later.

Given the volume of emails that they receive, it is very likely that your message will become lost under the pile.

#3. Keep your emails focused on one goal

Good email subject lines are clear and concise. As such, you must focus on one objective or takeaway from the email.

When you attempt to introduce multiple subjects or goals into one email subject line, you will lose any impact.

If the user feels confused about what action you want them to take, it is very likely that they will simply ignore the email altogether.

Keep it to one message per subject line.

#4. Know your audience

If your brand targets a youth audience that loves social media, you can embrace this.

Adding an Instagram caption or an emoji to your email subject line may have a significant impact.

Conversely, though, a B2B marketing email sent to C-level execs from an older generation may not respond well to this approach.

Subject lines must always work within the context of the overall marketing strategy.

#5. Be personal

Be personal

The impact of mentioning a person’s name has already been detailed above.

Personalization can extend to other aspects, though.

Cart abandonment emails are a great example that build on their past interactions with the brand.

Likewise, if the email follows on from a recent meeting, don’t be afraid to show you’re a familiar sender.

You can emphasize this point by setting your sender name to “[your name] at [company]”.

#6. Mention video

Consumers enjoy video content as it is entertaining, easier to digest, and capable of delving deep into a topic.

Mentioning the word video in the subject line can lead to increased open rates.

Moreover, you may want to integrate YouTube titles into the email content itself.

If the video feels relevant to their stage of the buying journey, the recipient will likely open the email to watch it.

#7. Add keywords

Keywords may not be as important to email subject lines as they are to blog posts or YouTube videos.

Nevertheless, many recipients will filter emails based on their emails, particularly in B2B circles.

Therefore, relevant keywords can play a vital role in ensuring that your emails get seen.

When combined with the other tips mentioned in this guide, the open rates will increase.

#8. Make recipients feel special

Even if you do not add personalized touches like their names, emails can make recipients feel special.

You can achieve this with terms like “VIP invite”, “Just for you”, or “For our best customers only”.

While this type of email only tends to work on customers that already love the business, it can lead to increased customer lifetime values.

Remarketing will bring greater ROIs than marketing to new leads – even through email.

#9. Try A/B testing

While you may think that you’ve perfected your email subject lines, the truth is that even a subtle update could make a huge difference.

A/B testing allows you to try several campaigns that include the same email only with different titles.

Track the success and open rates of each solution and you will soon be better positioned to optimize your emails.

Take note of what works for further assistance.

#10. Consciously monitor the emails you open

You are a consumer of emails yourself and can use this experience to your advantage.

When you next open an email from a brand, take a second to ask “what made me open that particular email?”.

If there is a specific factor that piqued your curiosity, it may be something that can be incorporated into your email subject lines.

An idea that worked on you is surefire to work on others. 

Consciously monitor the emails you open

Take your email subject lines to the next level

Effective email subject lines are the heartbeat of strong email marketing campaigns.

If you want to prevent them from ending up in a user’s spam folder, it’s imperative that you address the recipient and appeal to their pain points or emotional intrigue.

The above tips will help you do this effectively, although a little trial and error may be needed to get it right.

If you wish to avoid the stress of creating effective email subject lines, along with the threat of failed ideas, Optimo can do the hard work for you.

Simply tell the AI tool what your email is about and it will present 10 email titles in a matter of seconds.

The future of email marketing is here.

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