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New AI subject line generator makes a big first impression

Lana Abdallah Lana Abdallah
· 14 min read · Updates,Email marketing · Jul 20, 2023
Team members Agathe, Cesar and Abdullah (left to right)

The competition for inbox attention is fierce, and the subject line is your first (and sometimes only) shot to make an impact. A well-crafted subject line can be the difference between your email being opened or being lost in the shuffle.

Today, we're thrilled to introduce another new AI-powered tool in MailerLite that takes the guesswork out of creating powerful, engaging subject lines. 

Meet your new AI subject line generator! The innovative new feature that writes multiple subject lines for you based on what you need. Are you ready to save tons of time, increase your open rates, and make the most of your email campaigns?

Let’s take a look at how it works!

The new email subject line generator takes the challenges of crafting the perfect subject line and turns them into opportunities. Here are a few reasons why you’re going to love using this new tool:

💪 Maximize efficiency

Writing the perfect subject line can sometimes take as long as writing the email itself! But with the AI subject line generator, you can create a range of engaging subject lines in a matter of seconds. This means more time for creative tasks that can’t be automated.

💌 Enhance personalization

There’s no one-size-fits-all when it comes to email marketing. Every audience is different. With the help of your AI subject line generator, you can tailor each subject line to your campaign and audience, leading to higher relevance and, ultimately, better open rates.

🎨 Boost creativity

Struggling with writer's block? The AI subject line generator offers a plethora of creative possibilities. It can generate a variety of subject lines from a single prompt, providing you with a bunch of options that you might not have thought of on your own.

👊 Optimize subject lines for maximum impact

A well-crafted subject line can significantly boost the success of your campaign. With AI-generated subject lines, you'll benefit from optimized language that catches your audience's attention and encourages them to open your email.

The AI subject line generator is available on all Advanced plans. But for a limited time, you can try it for free on the new version of MailerLite! We’ve given all MailerLite accounts free credits to try out our new AI features (including free plan users). After all, seeing is believing.

To use the AI subject line generator all you have to do is create a new campaign or workflow email. Then, when you reach the ‘Subject’ field, click ‘Suggest’. A window will pop up where you can select your desired tone of voice and campaign type for context.

A screenshot of the subject line generator in MailerLite with the prompt

Then all you have to do is enter your prompt and hit ‘Generate’ to see a variety of subject line options.

A screenshot of the subject line generator in MailerLite showing 5 AI-generated subject lines welcoming people to an online cooking course

Pretty cool, right? You can either go with one of the subject lines generated or click ‘Regenerate’ for a fresh batch.

Get free AI credits for MailerLite

Sign up for a free MailerLite account and get free credits to use the AI subject line generator and AI writing assistant! Plus you can try even more premium features, like multi-trigger automation, pre-built templates and more, free for 30 days.

Sign up free

Having the ability to select your desired tone and campaign type helps the AI subject line generator understand your desired messaging goals. To give you a taste of how it can create lines based on specific requirements, we did a few experiments of our own.

Below are some examples of subject lines generated in MailerLite.

1. Promotional subject line example

Sending promotional emails can be tricky, especially if the hard sell isn’t really your thing. Luckily, with your new AI generator, you have an in-built sales team to do the hard work for you.

A screenshot of the subject line generator in MailerLite showing a promotional prompt with 5 AI-generated subject lines (listed below)

In the example above, we opted for a friendly tone to generate a subject line for a promotional email. Because we told the subject line generator what the offer and target audience are, it was able to bake in specific campaign information.


“Write a subject line promoting 15% off my leadership e-book titled "Leading Leaders" targeted towards female entrepreneurs”

  • Unlock Your Leadership Potential: Get 15% off on 'Leading Leaders' - A Must-Read E-book for Female Entrepreneurs!

  • Calling All Inspiring Women Entrepreneurs: Save 15% on 'Leading Leaders' - Your Pathway to Effective Leadership!

  • Empower Your Leadership Journey with 'Leading Leaders' - Get 15% off Now, Exclusively for Female Entrepreneurs!

  • Attention Female Entrepreneurs: Special Offer on 'Leading Leaders' - Grab Your Copy with a 15% Discount Today!

  • Exclusive Deal for Ambitious Women Entrepreneurs: Enjoy 15% off on 'Leading Leaders' - Unleash Your Leadership Potential!

But what if you’re looking for something with a bit more zing?⚡

Well, let’s take a look at what happens if we input the exact same prompt, except this time we’ll select the ‘Catchy’ tone.

A screenshot of the subject line generator in MailerLite showing the same prompt listed above but this time the

The same promotional information is relayed but in a totally different style.


Not sure which tone of voice resonates best with your audience? Create an A/B split test campaign and see which one gets the most engagement!

2. Announcement subject line example

The AI subject line generator can also lend a helping hand next time you want to announce a new product or feature.

A screenshot of the subject line generator in MailerLite showing a prompt with the

In this example, we included in our prompt that the goal is to get users to try our new feature. With that in mind, we made sure to choose the ‘Persuasive’ tone.


“This campaign is announcing our new AI subject line generator. The goal is to get users to try it.”

  • Discover the power of AI with our new subject line generator - Try it now!

  • Revolutionize your email marketing with our cutting-edge AI subject line generator!

  • Boost open rates and engagement with our brand new AI subject line generator

  • Unleash the potential of personalized emails with our innovative AI subject line generator

  • Get ahead of the competition with our game-changing AI subject line generator - Experience it today!

3. Newsletter subject line example

AI-generated subject lines don’t have to be reserved exclusively for limited-time offers and special announcements, you can use your new AI buddy to help your regularly scheduled campaigns as well!

A screenshot of the subject line generator in MailerLite showing a prompt with the

In this example, we told the AI subject line generator the topic of our newsletter and specified that our target audience is small business owners.


“Given the topic of A/B testing for landing pages, write a compelling subject line targeted towards small businesses.”

  • Boost Your Online Success with A/B Testing: Landing Page Tips for Small Businesses

  • Unlock Untapped Potential: Enhance Conversion Rates with A/B Testing for Small Businesses

  • Small Business Growth Secret: Learn the Power of A/B Testing for Landing Pages

  • Drive More Sales and Leads: A/B Testing Strategies for Small Business Landing Pages

  • Achieving Marketing Success on a Smaller Scale: Discover A/B Testing for your Landing Pages!

4. Event invitation subject line example

Writing an eye-catching subject line for your next event just got so much easier. All you need to do is give your subject line generator a few key pieces of information and let AI do the rest!

A screenshot of the subject line generator in MailerLite showing a prompt with the

In the example above, we wanted something a little more professional. We also limited our prompt to key information and keywords. It doesn’t take a creative mastermind to prompt this AI text generator. Take a look below at how stripped-back this AI prompt is.


“Webinar invitation on AI in email marketing. Get people excited for a surprise guest.”

…and how put together the AI-generated subject lines are!

  • Join us for an exclusive AI in email marketing webinar with a surprise guest!

  • Discover the latest AI advancements in email marketing - RSVP to our webinar now!

  • Don't miss out! Special guest announcement for our AI in email marketing webinar!

  • Unveiling the future of email marketing with AI – RSVP to our webinar!

  • Get ready for an extraordinary webinar experience on AI in email marketing!

5. Feedback or survey subject line example

Another great way to use the AI subject line generator is for survey emails. In this example, let’s take a look at how different keywords can affect the output.

A screenshot of the subject line generator in MailerLite showing a prompt with the

In the prompt above, we included that the goal was to make the subject line ‘intriguing’.


“Annual survey to gauge customer happiness for a project management app. The goal is to make it intriguing so subscribers open the email.”

  • Your voice matters: Take a moment to shape the future of our project management app!

  • Unlock the key to an even better project management experience - share your thoughts!

  • We want to hear from you! Help us improve our project management app today.

  • Calling all users: Join our exclusive panel to influence the future of our app!

  • Share your feedback and win exclusive rewards! Your opinion could shape our app's evolution.

Now let’s see what happens if we tweak that prompt, to make it more exciting. (For the sake of science, we’ll leave the tone and campaign type as they are).


“Annual survey to gauge customer happiness for a project management app. The goal is to make subscribers excited to open the email and reveal the survey.”

  • Tell us your thoughts and win: Take our customer happiness survey now!

  • We value your opinion: Participate in our annual happiness survey!

  • Help us improve: Share your feedback in our customer happiness survey!

  • Unlock exclusive benefits: Complete our annual survey and get rewarded!

  • Shape the future of our app: Take the customer happiness survey today!

6. Abandoned cart subject line example

Just when you thought it couldn’t get any better… Yep! You can use AI suggestions on your workflow email subject lines too. And what better way to take advantage of that than in your abandoned cart emails.

A screenshot of the subject line generator in MailerLite showing a prompt with the

Remember to test out other tones until you find the subject line that suits your brand’s abandoned cart emails.


“Casual subject line question for an abandoned cart email.”

  • Oops! Did something go wrong with your shopping cart?

  • Missing something? We saved your cart for you!

  • Did life get in the way of your shopping spree?

  • Is your cart feeling lonely without you?

  • Hey there, did you forget something on your shopping list?

7. Re-engagement subject line example

Finally, you can harness the power of AI to re-engage subscribers that haven’t been opening your emails in a while. If you’re offering an exclusive promotion for inactive subscribers, make sure to include it in your prompt!

A screenshot of the subject line generator in MailerLite showing a prompt with the

The more specific your prompt, the better.


"For people who haven't renewed their gym membership. Offering 3 months at half price if they sign back up before the end of the month. Lead with the benefit and focus on the reader."

  • Get Fit and Save Big: Enjoy 3 Months at Half Price When You Renew Your Gym Membership!

  • Transform Your Fitness Journey: Claim 3 Months at 50% Off - Our Welcome Back Gift to You!

  • Don't Miss Out on Your Best Shape! Renew Now and Get 3 Months at Half Price!

  • Rediscover Your Passion for Fitness: Join us Again and Grab 3 Months at an Unbeatable Price!

  • Reignite Your Fitness Goals: Sign Up Today for 3 Months at Half Price - Limited Time Offer!

And remember, if you don’t love any of the options the AI subject line generator has produced, you can always adjust your prompt and regenerate!

Well, folks, we're nearing the end of our announcement… but for you, the fun is only just beginning. You're now equipped with the power to make a grand first impression, thanks to your new AI subject line generator. Use your free AI credits to take it for a joyride, test out what works best for you and your audience take the guesswork out of email marketing for good.

Lana Abdallah
Lana Abdallah
I’m Lana, a Project Manager at MailerLite with a passion for delivering exceptional features. When I’m not managing multiple projects (or putting out the occasional fire) I enjoy spending time with my family and cooking Palestinian food.