13 A/B Testing Tools for Optimizing Email Subject Lines

Unlock the latest industry secrets straight from seasoned veterans in email marketing. Managing Directors and entrepreneurs reveal their go-to A/B testing tools for crafting perfect email subject lines. Starting with a recommendation for user-friendly Brevo and wrapping up with advice from marketing managers, discover the top choices from thirteen trailblazers. Dive in to explore these invaluable insights tailored to enhance your email campaigns.

Want to get quoted in MarketerInterview.com content just like this? Apply to become a contributor today!

Choose Brevo for User-Friendly A/B Testing

Regarding A/B testing email subject lines, Brevo (formerly known as Sendinblue) is an excellent choice. We found that one of the primary advantages of using Brevo is its user-friendly interface. We could set up A/B tests with ease, even if we don’t have a highly-technical background.

Brevo excels in offering comprehensive A/B testing capabilities. You can test different subject lines and experiment with various elements of your emails, such as content and sending times.

Another significant benefit is Brevo’s real-time analytics. We could monitor performance metrics as the campaign ran and assess which subject line was most effective almost immediately.

Segmentation options further enhance the platform’s effectiveness. By targeting specific audience segments, we could ensure that our A/B tests were relevant. Brevo also includes an automated winner-selection feature. Once the test concluded, the platform automatically sent the winning version to the remaining subscribers, maximizing engagement.

For a small company, such as ours, Brevo’s affordability was key to giving us the opportunity to use A/B testing with minimal effort.

Marco Cevoli, Managing Director, Qabiria

Use ActiveCampaign or Mailchimp for Split-Tests

For A/B testing email subject lines, I recommend ActiveCampaign or Mailchimp. Both platforms are user-friendly and allow you to easily run split-tests on subject lines, measuring which version gets higher open rates.

ActiveCampaign offers robust A/B testing features where you can test different subject lines and also compare variables like content, sending times, and audience segments. The platform provides detailed reporting to help you refine your email marketing strategy.

Mailchimp’s A/B testing allows you to test subject lines, content, and even sending times. It’s particularly useful if you’re looking for simplicity in setup and analytics.

Both tools provide automation and reporting, making it easy to make data-driven decisions about your email campaigns. If you’re running multiple tests or handling more-advanced sequences, ActiveCampaign may give you a bit more depth, but both are solid options.

Connor Gillivan, Entrepreneur, Owner & CMO, AccountsBalance

Opt for Litmus for Browser Compatibility

In the last 5 years or so, I have tried different email-testing tools. Most of them are very effective and help me verify my campaigns before mass sending. But one tool that I particularly like is Litmus.

It offers different solutions, but email testing across different browsers is its main and most popular feature. Apart from the email layout, you can test subject lines. For this, you need to go to First Impressions. If the subject isn’t optimal, the system will offer solution options.

By the way, you can do subject line A/B testing in eSputnik as well. When creating the campaign, specify two or more subject lines to test. At the launch, the system will automatically split the recipients into equal groups and send them emails with different subject versions. As a cherry on top, it can detect deliverability problems and help you hit the Inbox.

Kate Dzhevaga, CMO, Head of Growth, SYMVOLT

Select Klaviyo for E-Commerce Email Testing

Klaviyo is an excellent choice for A/B testing email subject lines. It offers a robust suite of features, including A/B testing, segmentation, and automation. Klaviyo is particularly popular among e-commerce businesses and is known for its ease-of-use and powerful analytics.

If you’re already using Klaviyo for other email marketing tasks, it might be a convenient option to leverage its A/B testing capabilities as well.

Erin Siemek, CEO, Forge Digital Marketing, LLC

Pick Instantly for Cold Email Campaigns

For cold emails specifically, Instantly is a really awesome tool. It is very affordable, and their entire platform is specifically built around cold emailing.

They have robust A/B testing built into the platform, including unlimited variations for the subject and body. You can easily see the analytics for the different variations and even automatically select the best one after a percentage of emails are sent. You can even set up A/B tests for multiple stages of an email-sequence flow.

They also have built-in warm-up tools to make sure your emails avoid the spam box as well as lead scraping for mass emailing. All included in a very affordable monthly price.

They even have domain purchasing and setup built into the platform so you don’t need to know the technical setup aspects of cold emailing.

Ben Miller, COO, Undetectable AI

Try Benchmark for Intuitive A/B Testing

Personally, I highly recommend Benchmark for testing email subject lines.

One of the platform’s best aspects is its very user-friendly, intuitive interface, which makes it easy to set up the tests without needing advanced technical skills.

Along the same vein, Benchmark excels at segmenting your audience for testing. Of course, this is amazing as it allows you to send different subject lines to specific groups, helping you understand how different demographics respond to various approaches. We can then analyze engagement metrics, such as open and click-through rates, to determine which subject line resonates best with our audience.

As the cherry on top of the cake, Benchmark integrates seamlessly with many email-marketing platforms, making incorporating A/B testing into one’s existing workflows easy.

Simply put, it has a user-friendly setup, powerful segmentation options, and comprehensive analytics, making it a pretty dependable solution for testing email subject lines.

Peter Bryla, Senior Community Manager, LiveCareer

Consider GetResponse for Multiple A/B Tests

GetResponse is a great option because it supports up to five A/B tests. It also has an easy-to-use interface. Its paid plans include 24/7 chat support, which is helpful for businesses as it allows them to provide guidelines or resolve issues around the clock. Lastly, it offers real-time analytics, which helps you monitor the results of your A/B tests and make data-driven decisions.

Jason Davis, Founder | E-commerce SEO Guru, Makarios Marketing

Leverage HubSpot for Robust A/B Testing

As an experienced inbound marketing consultant, I highly recommend HubSpot for A/B testing email subject lines. HubSpot’s email tool allows you to easily create multiple subject-line variations and see which has the highest open and click-through rates.

For example, a client wanted to drive more traffic to their new product page. We tested three different subject lines: “New Product Launch!” “Check Out Our Latest Innovation!” and “You Asked, We Delivered.” The third subject line drove a 22% higher open rate and 34% more clicks to the product page.

The key is to only test one element at a time, either the subject line, sender name, or content. Make small changes so you can clearly see the impact of each variation. With a tool like HubSpot, you’ll gain valuable insights into what motivates your subscribers and deploy the most effective emails.

A/B testing emails have helped many of my clients significantly improve their open and click-through rates, which ultimately boosts revenue. I recommend all marketers start testing today. 

Jay Owen, CEO, Business Builders

Implement SendGrid for Gaming Email Campaigns

SendGrid has been a total lifesaver for our gaming email campaigns, especially when it comes to A/B testing subject lines. We’ve seen insane open rates—like 40% higher than before—by using their tailored subject line options for different player segments. It’s super easy to use and integrates smoothly with our other marketing tools, which is crucial when you’re juggling multiple Minecraft community events and updates.

Jas Bola, Product Marketing, Minecraft Menu

Utilize VWO Engage for Effective Subject Testing

As an AI marketing expert, I rely heavily on A/B testing to optimize email campaigns for my clients. Based on experience, I highly recommend VWO Engage for email subject-line testing. 

VWO Engage makes it simple to create multiple subject-line variations and analyze how each impacts open and click rates. For a plumbing client’s recent promotion, we tested “Act Now – 15% Off Repairs” against “Emergency Plumbing Sale.” The latter yielded a 22% higher open rate, leading to a surge in call volume.

The key is testing one element at a time. Compare two subject lines, sender names, or call-to-actions. Make small changes so you can clearly see the impact of each version. With a tool like VWO Engage, you’ll gain valuable insights into what motivates your subscribers and deploy the most effective emails.

A/B testing emails has been pivotal for boosting clients’ marketing performance. All email marketers should start testing; you’ll achieve major gains in open rates, clicks, and revenue. 

Lesly Jean-Baptiste, Owner, Team Genius Marketing

Adopt Optimizely for Comprehensive Email Testing

As the owner of an agency that provides digital marketing services, I highly recommend Optimizely for email subject-line testing. We regularly use it to optimize email campaigns for our clients and have seen open rates increase up to 50% for some.

For one client, a local restaurant, we tested “Special Dinner Tonight – 50% Off!” vs. “Last Chance – Final Day of Sale!” The second option drove 60% more opens and a 15% increase in click-throughs. For small businesses, optimizing each email campaign can drive real impact on revenue and growth.

The key is to start simple by testing just 2-3 options for at least a day or two, then go with the clear winner. Don’t make endless small changes to squeeze out another percent or two—the real gains come from finding what resonates most with your audience. An email-testing tool is key, and Optimizely is easy to use while still providing powerful functionality for in-depth testing and metrics.

With email, small optimizations add up over time. Testing gives you data to make the right choice for each campaign. If you’re not testing, you’re guessing and likely leaving opportunities on the table.

Josh Hook, Agency Owner, Hook’d IT Up

Go with Mailchimp for Simple A/B Testing

Regarding testing email subject lines, I recommend using Mailchimp for A/B testing. I’ve found it an easy and effective tool for this purpose. You can test up to three subject lines at a time, allowing you room to play around with different ideas. It’s especially handy when sending emails to a large list because it automatically determines the winning subject line based on open rates.

What I like about Mailchimp is how simple the setup is. You don’t need to deal with complicated metrics. Write your subject-line variations, set your testing parameters, and hit send. It also provides clear insights afterward to see what resonates with your audience. No guesswork is involved.

From my experience, it’s good to test different styles of subject lines—like short vs. long or urgent vs. friendly tones. You’ll be surprised by what works. For example, I once ran a test in which a more casual subject line outperformed a more formal one. It wasn’t something I expected, but that’s the beauty of A/B testing.

If you’re just starting, keep it simple. Test one variable at a time, like changing just the subject line. It’s a great way to see what catches attention and how your audience reacts.

Kate Donskaia, Marketing Manager, WealthProtector

Stick with Your Current Email Tool

We recommend whatever email tool you are currently using! As long as you’re doing A/B testing, you’re doing something right. Some email tools, like HubSpot (which we use and like), have built-in features to split your email list; and with others, you have to do it manually, but it’s still doable. So, whatever tool you choose to use, thank you for testing and doing email better!

Brittany Reith, Marketing Manager, 9 Clouds

Want to get quoted in MarketerInterview.com content just like this? Apply to become a contributor today!