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How to Do Email A/B Testing
8 min read

How to Do Email A/B Testing

How to Do Email A/B Testing

Oftentimes, you will not find the best approach to engaging with your contacts, subscribers, customers, or prospects on the first try. Your email strategy is perfectible but knowing how to adjust it takes time, effort and requires data that can point you in the right direction. You will need to test out various assumptions or hypotheses, compare results and stick with what works best. But to really do that, your work has to be disciplined, you will need to have a strict and serious system in place for testing out hypotheses and also a clear standard for picking a winner out of the variations you are playing with.

Email A/B testing principles

Email marketing A/B testing means identifying areas that could benefit from improvement, launching some theories regarding what kind of changes could bring in the best results, implementing those theories, and deploying campaigns based on these assumptions, so that you can collect actionable data.

Here are the elements of an email marketing campaign that you can subject to an A/B test:

Subject lines

Subject lines being the first thing subscribers see when interacting with your email communication can be the most powerful asset you have to entice them with. A well-written, memorable and impactful subject line will make a lot of difference in terms of engagement, especially when it comes to emails opened. As long as you get your customers through the door, you have achieved half of your goals already. When testing out different subject lines for your email campaigns, always make sure that you use a copy that stands out, but not by being aggressive, spammy, or unprofessional. You might want to try using emojis if they feel natural to your business and target audience, but do not overdo it. A subject line that is crowded and feels desperate, or acts like clickbait will most likely lead to an unsubscription, rather than a positive engagement.

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Subject lines that highlight a benefit will bring in the best results. Try to underline the incentive you are offering to your subscribers from the get-go. Users are so inundated with emails that they need to have a grasp on what your communication is about even before opening it. Are you sending them a valuable piece of inbound marketing content? Then it is only a matter of packaging that ebook, article, whitepaper, video, or webinar in a way that will get you their attention.

Another great idea is to try to include positive emotions in your subject lines. People most often respond well when they feel safe, valued, and protected. If your brand can convey these essential emotions, use that strength to boost your email campaigns. Talk about wellness, increasing confidence, celebrate your subscribers and make them feel noticed.


Another element that requires your special attention is your email’s image or images. If you have the option to add an image to your email, always go for it. It will not only give your emails a more visual appeal, but it will also help create consistency between multiple deployments. But there is one aspect you will need to keep in mind when adding images to emails. Some email clients might block your images and the subscriber will not see anything except for a blank space where the image should be. Make sure to add undisruptive assets to your email and if you are using background images you will also have to change the fallback color of your background so that any text will be readable.

Email marketing campaigns can be highly effective when they include an image that is relevant and compelling. If you are doing your email marketing campaigns in-house, make sure that the images you are using are fresh, distinct, and fit your overall brand identity. If you are outsourcing your email marketing campaigns, make sure that you have clear guidelines in place about what kind of images to use.

For A/B testing purposes, you could try different color schemes, different visual elements or different texts on your images. Test out one hypothesis at a time, by changing just one element and perfect your images over time. On the other hand, if you want to check the impact in terms of engagement by employing A/B testing for images, you could also try different image sizes or resolutions. Try to find a balance between making your image too large and overwhelming your subscribers, and making it too small in a way that is no longer conveying your message effectively. Lastly, you can find the best approach to images in your emails by A/B testing aspects such as contrast, the way you are using white space or whether you place a call to action there or not.

Email body

Email body copy is probably the most important factor that will determine the success of your campaigns, other than the subject line that you pick. Another important factor that you should not ignore when testing subject line ideas. If your subject line has managed to get your subscribers to open a message, what you have to focus next on is how you use the body of your email to lead them to take action, either to go to your shop, register for an event, read an article or offer you feedback on their experience. As long as your email body copy is strong enough to convince them, it has done its job. You will want to use your email body copy to give the subscribers all the information they need to know about your offers, promotions, or announcements. Where applicable, do not forget to mention the deadline for the offer or the deadline for registering for an event.

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But what exactly can you test when it comes to the email body copy? First, see how different formats impact engagement. Try formatting your text in a way that helps email skimmers understand the information quickly. You can use bullet points, place sections of your text in bold, or make some portions of the email body in a larger font. You would be surprised how efficient these measures can be.


Calls-to-action are a great way to convert leads into customers. A call-to-action button is essential for any email marketing campaign that is intended to drive engagement and conversions. Make sure that the CTA button is clear, that it stands out and that you do not over-do it and place too many of them in a single email.

For A/B testing CTAs, the best approach you can go with is to change the color scheme and size of the button, while also testing out different text formatting. Will your subscribers become more engaged when you include a button that uses a different color than the rest of your email? Are they more likely to click on the button if the text is more prominent? These are all questions that you want to find answers to.

Ultimately, do not disregard the importance of a good and catchy copy for your call-to-action. This is another factor that might positively impact email marketing metrics if you find the formula that best suits your subscribers. Do not be afraid to test out ideas that you have never tried before when generating the copy for CTAs. If you are trying to stand out and convince subscribers to interact with your email, maybe thinking outside the box is the thing you are missing. MailUp, one of our native email verification integrations, offers a great in-depth article on how to A/B test an email call-to-action.

The email delivery time

Changing the look and feel of an email, or testing out different messages are guaranteed to offer you insights into what your subscribers are expecting from your email campaigns. But you could also pay attention to the email delivery time because it will help you figure out when your subscribers are expecting to get your emails.

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Try to test out the most popular times, such as first thing in the morning, when people are getting ready to start their workday; late afternoon, when people are wrapping up their work and are starting to relax; and early evening, when people are getting ready to end the day. Also, you want to try out different days of the week, and also different times during the week. Some people may be more engaged during the week, while others are more active on the weekends.

Personalization/Sender name

Personalization is a powerful tool for getting the attention of your contacts. Depending on your email service provider, if you can personalize emails, you have a much higher chance of engaging them and making them feel a sense of belonging, while also increasing the likelihood of transforming them into brand ambassadors. Personalization is a distinct aspect of conversion rate optimization, but we are including it here because of the benefits it can bring to your campaigns.

Analyze what is possible and what not in terms of email personalization and find the best placement for it inside your deployments. When you are setting up an email program, try to include fields that directly relate to your customers. Pick from demographic fields, such as their company name, their industry or country, especially for B2B subscribers, or gender, age or parental status for B2C ones.

Dynamic content can also help you deliver personalized emails based on the information you have already gathered about your contacts. With dynamic content, you will be able to create a single email that addresses the needs or priorities of segments of your email list. Learn more about how dynamic content and personalization can benefit your email campaigns from CampaignMonitor.

Social media sharing buttons

These are a great addition to any email marketing campaign. Referencing your social media channels in email campaigns can be a great way to further engage subscribers on different platforms. Make sure that your potential audience can easily share your content on social media channels, as well. After all, the more people you can reach, the better the results will be.

If you want to grow the number of clicks to your social media accounts, use A/B testing to try out different social media icon styles, colors, shapes or simply change the position of these icons.


Now that you know the different elements of your email marketing campaigns that you can test out and how to test them out, the next step will be to come up with hypotheses for your tests. This will be the most impactful task in the A/B testing process and will ultimately determine whether you will collect actionable data or not.