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What is A/B Testing in Email Marketing?

by Christine Williams
Read Time: 7 minutes
A/B Testing in Email Marketing

If you are like me, you really want a green thumb but have trouble keeping plants alive. Recently, I bought two of the same plant and placed them in different areas of my home. I wanted to find the best spot in my house for this type of plant to grow and thrive. Both plants received the same water and care but are subject to different amounts of sunlight.

This rather silly experiment I performed in my home is an A/B test. I am only changing one variable – sunlight – to see which plant responds better.

Now, you may not be testing your plants at home, but you are most likely doing some form of A/B testing in your everyday life.

"A/B testing is a marketing experiment where two variations of a landing page, ad, email or other piece of online content are pitted against each other to determine which produces the highest conversion rate. - Unbounce Conversion Marketing Glossary

While you can (and should) A/B test marketing assets like ads, landing pages, and other digital content, in this article we are going to dive into A/B testing specifically for email marketing.

How A/B Testing Works for Email Marketing

A/B testing is rather simple. You select a group of contacts, create 2 different versions of an email, select what percent of the contacts you would like to test, determine what qualifies a winner over a period of time, hit send and wait for your results.

Let’s break that down...

You want to send an email to a group of 500 contacts. You select 30% as your test group, your variable is the subject line, and the winner is based on clicks over a two-day time period. Your A/B test would look something like this:  

  • Your test group of 150 will be selected at random from your group of 500. 
  • You will write two different subject lines, but the rest of your email will remain the same.
  • Email A with your first subject line will be sent to 75 people.
  • Email B with your second subject line will be sent to the other 75 people.
  • After 2-days, the remaining 350 will receive the email (A or B) that received the most opens over that two-day time period.  
  • Your report will have statistics on both tests and your final email. 

Most email marketing platforms walk you through these choices step by step. Take DirectLync for example below. This makes it easier on the user as they walk through the first part of the process.

1. Setup:  DirectLync walks you through how to correctly set up your A/B test. 

2. Select your variables: This is where you select what you would like to test. Most platforms make it easy for you to see the changes to your test groups.

3. Create your options: Since I selected subject line as my variable above, it gives me two subject lines to create.

4. Build your email: This is the same email editor you always use to build your emails. 

5. Confirm: Schedule or send your email and wait for the results to roll in!


Why Should I A/B Test my Emails? 

The better question is why would you not want to A/B test your emails? To me, it’s a no brainer. For a minimal amount of additional work, you get way more in rewards. By incorporating A/B tests into your email marketing strategy, you can better understand your subscribers’ preferences in order to send them more personalized content. That will ultimately lead to better results and a more engaged audience.

After a few A/B tests, you will start to see patterns and be able to identify the factors that lead to more opens, clicks, and conversions. That means you will be getting more views of your brand, more visits to your website, and (hopefully) more purchases.

Starting my A/B Test Email 

Now that you are convinced you need to use A/B testing, you are ready to start building your emails. But first, you need to have a plan. It’s important to know your audience and what you are trying to influence. 


When you are selecting the segment from your database that you would like to send an email, think about their characteristics and interests. What do they have in common? How have they interacted with previous emails? Are they very engaged or is it a dormant list you are trying to reactivate?  

Based on these questions, you can better tailor the content in your email to match their preferences and begin to think about how you want to influence them in the email. 


Influence is referring to your goal. How are you judging the success of your email?  Are you trying to increase click rate, conversions, subscribers, or understand the best time to send to your audience? The answer of this question determines the variable you choose for your A/B test.  

Most email A/B tests let you choose from multiple variables such as:

  • Subject Line
  • Content & Design
  • Sender Name

We recommend that you only choose one variable to test at a time. Otherwise, you will not be able to identify the exact variable that caused high-performance rates. 

Building Your Emails

Depending on the variable you choose, there will be different ways to change and customize your A and B email options. 

Subject Line

Fairly self-explanatory, but the subject line tests the effectiveness of two different subject lines.  For example, you may want to test two different subject lines to see which gets more opens.  

Check out these 5 digital marketing tips vs. 5 Digital Marketing Hacks to Increase Lead Generation

Or telling more about what you will find inside by adding a whitepaper or video to the front of your subject line. 

[Whitepaper] Digital Marketing Tips to Grow Your Business vs. Check out these digital marketing tips

By testing different subject lines, you can identify what makes this audience open your emails. For subject lines, we recommend that success is based on open rates. 

Content & design:

The options are endless when you are testing the content or design of your email in an A/B test. You can test different tones, personal email vs. a marketing email with imagery, or the location of your CTA button on the page. 

Here is an example of how we tested a case study. The first is an email from a salesperson and the second is a marketing email with a visual story. 

Sender name

Similar to testing subject line, you may also want to test the sender name. Are you getting more clicks when you send from or from By keeping your subject line, content, and design the same but just changing sender name you will be able to identify the right email address for future emails. 

Send date and time

Every audience is online at different times in the day. 


There have been many studies done on the best times to send emails (like the one above by Propeller). These are fantastic benchmarks to use, but your audience may be different. It doesn’t hurt to test different send times to see how your audience responds.

The more you test, the more you will know about your audience!

Give it a Try

The only way to know if A/B testing is right for you is to try it! Start with your next email campaign. AB Testguide gives you this nifty calculator to help figure out the right number to test based on your group size. 

Determine what you want to test and watch the results come in. Test regularly to get a feel if your results were a one-time reaction by your group or if they stand true over time. You can use these insights to tailor future communications to this group and start having more engaged subscribers!


Go forth and start testing!