A/B Testing Email Campaigns: Everything Important You Need To Know

Narayani Pandya

Narayani Pandya

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The marketing field has witnessed a 360-degree revolution in the past few years. From webinars, video campaigns to infographic content, there’s been a lot of experimenting.

However, one campaign that has remained efficient and will continue to do so is the email marketing campaign. New and unique campaigns can certainly add value to your proposition, but emails will always remain classic.

In fact, there are 4 billion email users currently, and the number is expected to climb to 4.6 billion by 2025. So, you can only imagine the impact email marketing has on every kind of business.

Your business may have a diverse demographic with different preferences; therefore one type of email campaign won’t work on all of them. This is where A/B testing of emails becomes necessary.

How does A/B testing help in email marketing campaigns?

In A/B testing, you set up two variations of your email campaign and send them to your subscribers. Later, you can measure the success of your email campaigns by finding out which variation got more responses.

When you’re running an important campaign, you expect the results to be positive. And the only quick and effective way of testing your email campaign on a small number of subscribers is by executing A/B testing.

Even now, many marketers aren’t well aware of how A/B testing in email marketing works. Trust me when I say that this simple process of creating two variations of a campaign will bring substantial growth to your campaign.

Therefore, to measure the success of your email body images, or even just a subject line, split your emails into two and send it to your subscribers. As a result, you’ll have a clear vision of which idea works and which one needs to be discarded.

Why do marketers implement A/B testing in email campaigns?

A/B testing not just focuses on the entire email; it can also be executed by targeting various parts of your email.

Here’s what insights marketers get by implementing A/B testing - 

  • Finding out whether their audience is amused by the use of gifs or emojis or not.
  • Which content is catching more attention of the subscribers?
  • Which type of CTA button is bringing more email click rates.
  • Which graphic is connecting better with the people

Once you have the email campaign insights, you can make an informed decision and go ahead with the campaign that brought the highest amount of open and click rates.

Various ways you can test your email campaign

The best part of A/B testing is that you can experiment with every element of your email; from the subject line to its images, you can test every element and understand its performance.

A/B testing subject lines

A powerful and catchy email subject line is the one that captures your attention at first glance.

The subject line is the first thing your subscriber will look at when they open their inbox, so you need to impress them right away. Anything below average, and the email will go into the trash!



A/B testing of subject lines
Image source 

The above image is the perfect example of A/B testing of subject lines. Here, they have used numbers and discount percentages while the second one just informs about the season sale.

Which subject line grabbed your attention first?

For me, it was Subject Line A. It is very crisp and goes right to the point - providing a 15% discount on the next purchase. Therefore, if I’m a customer that wants to purchase from them, I’ll go straight to their website and purchase it if I receive the first subject line.

The second subject line also announces the season sale, but it’s very vague, so a busy person might not open it.

A/B test images

Once you’ve enticed the subscriber with your eye-catching subject line, it’s time to play with visuals and images. 

It’s a human tendency to first glance at an image whenever a piece of content is presented. Therefore, ensure that you split the test - one with images included in the email and one without.

Use bright and happy colors in your images and make them super fun to look at! This will drive your reader’s attention, and they’d be more likely to take action.

Moreover, the current generation also loves watching videos and gifs. So, you can also add a few video clips into your email body and check whether it’s working or not.

A/B Test copywriting

Along with another element of the email, the content of the email body also plays a pivotal role in your email campaign.

Even the tiniest placement and word choice can impact your email.

screenshot showing increase in conversion rate through slight variation
Image source

We all love free products and resources, right? The above image added “It’s free!” in their second variation and witness how their conversion rate increased drastically. You need to offer something that’s truly irresistible and makes your reader want to take immediate action.

This is the power of content in the email body. Therefore, whenever you’re writing an email, ensure that the information is clear and to the point.

A/B test call-to-action

CTAs are highly crucial for any email campaign; that small CTA button is what’s going to take your reader to the desired landing page. Hence, you can also test call-to-action and try out different variations.

CTA is usually added at the end of an email, or you can place it in the middle as well if the email is lengthy. At this time, you need to make sure that the CTA added stands out from the rest of the content so your reader will be persuaded to click on that button.

Many marketers and researchers also play with the colors of CTA buttons as the bright color tends to draw more eyes compared to dull colors.  Moreover, CTA content also has an impact on your readers.

So, these are various ways you can test the elements of your email content and finalize the one that receives the highest response from your readers.

Factors to consider when running A/B testing email campaigns

A lot of precision goes into running A/B tests on email campaigns, so there are also certain factors that you need to consider before you push your A/B testing live.

  1. Choose the sample size

Once you finalize which element you want to test (Subject line or product image), you need to choose the sample size of your A/B testing.

When executing A/B testing, you should avoid splitting your variations in between all your customers, especially if you have an email list of over 1000 subscribers.

Pick a small subset of your recipients, say about 20-30%, and based on their response, the winning email copy will be sent out to the rest of the subscribers.


bar showing sample size of two groups and winning version
Image source


In the above image, 56% of subscribers are selected for A/B testing. So, from the actions of this 56% of the readers, a winning variation of your email will be decided, and that email copy will be sent to the remaining 44% of your readers.

  1. Add the criteria for winner selection

Before you run the test, ensure that you have selected either total unique clicks, open rates, or total clicks on the selected link. You need to decide on a KPI for the campaign. This will be the criteria for declaring the winner, and it can’t be changed once you have executed the A/B testing. Therefore, it’s crucial to select it beforehand.

If you’ve selected open rates, then at the end of the test, you’ll get results based on the open rates of both variations.

  1. Consider the timing window for running the test

Always remember that this entire process takes place before the execution of your email campaign to the majority of your subscribers. So, consider that factor when you set the timing for the test run.

The length of your test run can range from one hour to 4-5 days. However, in this case, a longer waiting time doesn’t always guarantee an accurate response.

For instance, testing out newsletters on existing subscribers can have a shorter time compared to your product or feature launch campaign.

In fact, when it comes to opens, 2 hour wait time provides 80% accuracy, and wait time of 12+ hours provides 90% accuracy.

For clicks, 1 hour wait time gives you 80% accuracy, while a wait time of 3+ hours provides 90% accuracy. So, if you’re not in hurry, waiting for one day can derive the most accurate results.

  1. Set up the right delivery time

Along with the content of your email, the delivery time also matters a lot when you’re trying to reach more people. Hence, you need to research and find out the best time for sending emails to your subscribers.

After that, once your A/B test ends at 10 am after running for two hours, your remaining email subscribers will automatically get the winning email at 10 am.

This setting also needs to be pre-determined, so the right time for sending emails is 1 pm for you, then you can set up the test at 11 am so it ends at the exact time.


  1. Test one variable at the time

Testing only one variable is an unwritten rule of A/B email testing. If you want to draw accurate results, you can only test one variable at a time.

Example #1 -  The correct way of running the A/B test would be to create two variations with different subject lines and keep everything else similar. 

So, when you see that the second email has more open rates, you’d know that it’s because of the subject line.

Example #2 - So, you created two variations of your subject line, and along with that, you also changed the image placement in the email.

Now, when the results emerge, you wouldn’t be able to bifurcate between two variations and find out whether the subject line worked for your audience or the images.

  1. Measure your success

Now that you’re sending out different versions of emails, it’s essential to determine the factor for measuring the success of your campaign.

If your conversion rate from previous campaigns is 17%, you need to draw the stats of conversion rate from your current campaign with A/B testing. If the conversion rate is more than 25%. You can consider it a success.

Best practices for A/B testing email campaigns

By now, you must feel like you can easily set up an A/B test for your next email campaign, and trust me, you certainly can. 

To ensure that your A/B testing runs smooth, I’m listing down best practices that many marketers follow which can help you as well

  • Use the control version of your email, i.e., the email that you would’ve sent originally to your subscribers.
  • To capture every change in trend or your customer’s behavior, it’s important to test simultaneously.
  • Add testimonials in your email body and see how your readers react to it. Generally, positive feedback does help you in gaining the trust of your customer.
  • Localizing the content of the email is also a good technique to get more actions from customers.
  • Personalization goes a long way! It’s even better if you personalize the subject line of the email with the subscriber’s name.
  • Let go of the personal bias for a specific email copy that you favor and listen to the statistics.
  • For best results, test early and more frequently.
  • Keep experimenting and test different elements of your email.
  • Use certain tools that can help you in easier A/B testing.
  • Always test only one variable at one time. In case you want to test more than one email variable, you need to check out multivariate testing.

By following these simple practices, you can create and execute A/B testing without any hassle!

Well, A/B testing is not being used for email marketing only; marketers love to experiment with content, landing pages, CTAs, and every tiny thing that helps to engage more with their customers. 

Many brands use A/B testing with invoices also. You can use two different invoice templates and send that out to the two sets of clients. You can evaluate how your clients react to it.

Final thoughts

A/B testing of email can prove to be highly beneficial for your campaign, so if you haven’t implemented it yet, now’s the time to do it. 

By running a split test, you determine the best for your subscribers and honor their opinions, which in return may help you in building lasting relationships with your customers.

Moreover, even after you’ve successfully run your email campaign, I’d suggest you keep testing out the emails to get a better grip on your emails and understand the customer preferences.

Author Bio

Narayani Pandya

Narayani is an enthusiastic digital marketing professional, having work experience in sales and customer experience in the past. She enjoys having a cup of tea and walking on the grass when not working.

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