When It Comes To Email Marketing, What Do We Mean By The Term A/B Testing?

July 24


When It Comes To Email Marketing, What Do We Mean By The Term A/B Testing?

By Hanson Cheng

July 24, 2023

  • minute read
  • Last Updated on July 24, 2023 by Hanson Cheng

    A/B testing is a common term used in email marketing that refers to the process of comparing two versions of a marketing message. This method involves sending two different versions of an email to a small segment of subscribers in order to determine which version performs better in terms of engagement or conversion rates. By analyzing the results from the test, marketers can gain insight into what works and what doesn’t, allowing them to optimize their email campaigns for maximum impact. In this article, we will dive deeper into the meaning of A/B testing in email marketing and explore its benefits and best practices.



    Email marketing is a digital marketing strategy that utilizes email to deliver a marketing message to a group of individuals. In order to effectively use email marketing, businesses must employ various tactics to improve the performance of their email campaigns. One such tactic is A/B testing, also known as split testing or bucket testing. A/B testing can be defined as the process of comparing two different versions of an email to determine which one performs better.

    This is done by randomly dividing the email list into two groups, with each group receiving a different version of the email. By measuring the performance of each version, businesses can gain insights into what works and what doesn’t. A/B testing can help optimize various aspects of an email campaign, including the subject line, body content, calls-to-action, images, font, layout, and more. Essentially, A/B testing allows businesses to make data-driven decisions and constantly improve the effectiveness of their email marketing campaigns.


    Email marketing plays a vital role in modern-day online business by connecting brands to their customers through carefully crafted email campaigns. With the increasing number of emails that consumers receive in their inboxes on a daily basis, it’s essential that businesses create campaigns that are not only engaging but also effective. This is where A/B testing comes in. A/B testing is an experimental approach to email marketing that involves sending two different versions of an email to a subset of subscribers to determine which version performs better.


    Email marketing is a powerful tool in a marketer’s arsenal, but to truly unlock its potential, savvy marketers turn to A/B testing. A/B testing, also known as split testing, is a process where two versions of a marketing campaign are sent to a subset of a company’s email list, with the goal of determining which version performs better. The winning version is then sent to the remaining portion of the email list. The benefits of A/B testing are numerous.

    First and foremost, it allows marketers to fine-tune their campaigns, ensuring that the message resonates with the audience and drives the desired action. It also helps marketers understand which subject lines, calls-to-action, and other elements of a campaign are most effective, which in turn can inform future campaigns. A/B testing also takes the guesswork out of marketing, allowing marketers to make data-driven decisions based on real-world results.

    This leads to increased ROI and a better overall understanding of the audience’s preferences and behaviors. Lastly, A/B testing allows marketers to innovate and try new things, without risking the entire campaign or alienating the audience. By continually testing and refining campaigns, marketers can stay ahead of the competition and stay relevant in a rapidly changing digital landscape.

    Types Of A/B Testing

    Subject Line

    A/B testing, also known as split testing, is an essential process in email marketing that can help businesses to identify the best email campaign design, content, and subject lines that would resonate well with their target audience. One of the most vital components of any email campaign is the subject line, as it is the first impression that readers have of an email, and it can significantly impact email open rates.

    The subject line is a concise summary of an email’s content that aims to capture the attention of the reader and entice them to open the email. To determine what type of subject line works best, A/B testing can be used to test different variations of subject lines, such as using emojis, posing questions, or using numbers to create urgency, among others.

    The types of A/B testing that businesses can use when testing subject lines include:

    • Length Testing: This type of testing involves experimenting with the length of subject lines to determine the optimal length that would increase email open rates. Length testing can involve testing subject lines with a few words, up to longer subject lines that include more descriptive text.
    • Personalization Testing: This type of testing involves creating personalized subject lines that address the reader by name or interests to increase engagement. Personalization testing can include testing different variations of personalized subject lines to determine the most effective approach to use.
    • Emojis Testing: This type of testing involves adding emojis to the subject line to create excitement and increase email open rates. Emojis testing can involve testing different emojis and the placement of the emojis in the subject line to identify the most appealing combination.
    • Question Testing: This type of testing involves posing questions in the subject line to create curiosity and encourage readers to open the email. Question testing can involve testing different types of questions, such as open-ended, multiple choice, or yes/no questions, to find the most effective approach.
    • Urgency Testing: This type of testing involves creating subject lines that create a sense of urgency, such as limited time offers or deadlines, to encourage readers to take immediate action. Urgency testing can involve testing different variations of subject lines that include phrases like “hurry,” “last chance,” or “expiring soon.”

    By testing different types of subject lines, businesses can gain valuable insights into what types of subject lines will resonate best with their audience, thereby increasing email open rates, engagement, and ultimately, driving conversions.


    When conducting A/B testing in email marketing, it’s important to consider the type of content being tested. This can include everything from the subject line to the body copy, images, call-to-action buttons, and even the sender’s name. Testing content can reveal what type of messaging resonates most effectively with your audience.

    Subject line testing can help determine which language and tone grabs the most attention and generates the highest open rates. Testing body copy and images can reveal the optimal balance between informative and promotional content, and what visual elements are most appealing to your audience. Call-to-action button testing can determine what language and placement encourages the most clicks, while sender name testing can help you identify the most trustworthy and recognizable sender.

    However, it’s important to remember that content testing should be conducted in incremental changes, rather than complete overhauls. Testing too many variables at once can lead to inconclusive results and make it difficult to determine the specific element that had the biggest impact on results.


    One of the most critical elements of any email marketing campaign is the call-to-action (CTA). This is the point where the recipient of the email decides whether to take the desired action, such as making a purchase or signing up for a newsletter. However, crafting an effective CTA can be challenging. This is where A/B testing comes into play. By creating multiple versions of the call-to-action and testing them against each other, marketers can determine which version is most effective at driving conversions.

    There are several key factors to consider when creating and testing CTAs. First, the language used in the CTA should be clear and concise. The recipient should immediately understand what action is being asked of them. Additionally, the CTA should be visually appealing and standout within the email. This can be achieved through the use of contrasting colors or bold fonts.

    The placement of the CTA within the email is also important. Testing different locations, such as at the beginning or end of the email, can help determine which placement drives the most conversions. Furthermore, the number of CTAs within an email can impact conversion rates. Testing different amounts of CTAs within an email can help determine the optimal number for driving conversions.

    The design of the CTA button can also impact conversion rates. For example, testing different button colors and shapes can help determine which design is most effective at catching the recipient’s attention and encouraging them to click. Additionally, the text used on the button should be specific and action-oriented. For example, “Buy Now” is more effective than “Learn More.”

    Testing the CTA on different devices is also important. With the increasing use of mobile devices for email, ensuring that the CTA is optimized for mobile viewing is crucial. Additionally, testing the CTA on different email clients, such as Gmail or Outlook, can help ensure that the CTA is displayed correctly regardless of the client being used.

    Sender Name

    One important aspect of A/B testing in email marketing is testing different sender names. The sender name is the first thing recipients see when receiving an email, and it can significantly impact whether or not they open and engage with the email. A effective sender name can increase the open rate, click-through rate, and ultimately drive conversions. There are various types of sender name A/B testing that email marketers can try to optimize their sender name performance.

    The first type of sender name A/B testing is to test using a person’s name versus a company name. Some marketers choose to use a person’s name as the sender name to make the email appear more personal and authentic. On the other hand, using a company name can help establish credibility and authority.

    An additional type of sender name A/B testing is to try including a specific product or service in the sender name versus using a more general name. For example, instead of using the company name, “XYZ Inc.”, a marketer could test using “XYZ Sales Team” or “XYZ Customer Support” to see if it improves open rates and engagement.

    Another consideration for sender name A/B testing is the length of the sender name. Some studies suggest that using shorter names can result in higher open rates, while longer sender names may appear more formal and authoritative. Marketers can try using abbreviations or nicknames as well to see if this impacts results.


    One critical aspect of A/B testing in email marketing is finding the optimal sending time for an email. The timing of sending an email can impact open rates, click-through rates, and ultimately, conversions. Timing tests involve sending the same email to different segments of a subscriber list at varying times to pinpoint when recipients are most likely to engage with the content. Testing at different intervals throughout the day, week, or month can reveal patterns in audience behavior.

    For example, testing might find that a B2B audience is more likely to engage with emails sent on weekdays, while a B2C audience is more likely to engage with emails sent on weekends. Additionally, testing can reveal optimal sending frequency intervals. It’s important to strike a balance between regularly contacting subscribers and bombarding them with too much content, which could lead to them unsubscribing.

    How To Conduct A/B Testing

    Step 1

    A/B testing is a fundamental process of email marketing that allows marketers to evaluate the effectiveness of their email marketing campaigns. This process involves creating two versions of an email with distinctions in attributes such as text, images, call-to-action (CTA) placements, and subject lines. The purpose of A/B testing is to determine which version of the email is more successful in achieving the desired objective, whether that be a higher click-through rate or increased open rates.

    Step 2

    The second stage of conducting A/B tests in email marketing entails identifying the metrics to test impact. This is a crucial step that requires marketers to pilot test variables against the performance of their existing campaigns, determine what works and what doesn’t, and refine their hypotheses. Marketers should begin by determining the goals and key performance indicators of the test, the variables to test, and the elements to compare against the control group.

    Next, select the size of the sample population and determine the frequency and length of the test to ensure the statistical significance of the results. In this stage, it’s essential to begin with a hypothesis and use data-driven insights to modify and refine it. Testing should focus on discrete messages, including subject lines, headlines, call-to-action, layout, visuals, content length, copy, offers, and sending schedule, among other elements.

    Step 3

    In email marketing, A/B testing is the process of comparing two versions of an email campaign to identify which one performs better. To conduct an A/B test, you must first identify the variable you want to test and create two versions of the email: one with the variable present and one without it. The variable can be anything from the subject line, the call to action, the tone of the email, or the layout. The email list is then split randomly into two groups and each group receives a different version of the email.

    The performance of each version is then measured to determine which one achieved the desired outcome, which could be higher open rates, click-through rates, conversions, or revenue. A/B testing is a powerful tool for optimizing your email marketing campaigns, as it allows you to test different variables and make data-driven decisions based on the results.

    By continuously testing and optimizing your emails, you can improve the effectiveness of your campaigns, increase engagement with your subscribers, and ultimately achieve better results for your business. However, it’s important to ensure that you only test one variable at a time to obtain accurate results, and that you have a sufficient sample size to make statistically significant conclusions.

    Step 4

    The fourth and essential step in A/B testing is the implementation of the test. Once you have identified your goal and chosen your testing variable, you will need to determine the sample size, select your audience, and create two versions of your email. It is important to only test one variable at a time for accurate data. This could include changes to the subject line, call-to-action, images, or even the layout of the email.

    Once you have created your two versions, it is important to send them to a random sample of your email list. You may want to segment your audience based on demographics or previous purchasing behavior, as this could yield more insightful data. When sending the emails, include a tracking link to collect metrics on open rates, click-through rates, and conversion rates.

    Step 5

    One of the most critical parts of email marketing is conducting A/B testing. This process involves sending two different variations of an email to a small subset of the mailing list and monitoring their response rates to determine which version performs better. By using A/B testing, marketers can make data-driven decisions about how to optimize campaigns and ultimately increase the ROI of email marketing efforts.

    Before conducting A/B testing, it is crucial to establish the key performance indicators (KPIs) that are most important to measuring email success. These metrics may include open rates, click-through rates, conversion rates, unsubscribe rates, and revenue generated from email campaigns. By determining which metrics to track before conducting A/B testing, you can ensure that the results will be meaningful and actionable.

    When conducting A/B testing, it is also essential to ensure that the test is statistically significant. This means that the sample size of recipients being tested is large enough to produce results that are representative of the entire mailing list. Most email marketing platforms offer built-in A/B testing capabilities that will automatically calculate the statistical significance of results based on the size of the test group, but it is still important to be aware of this factor when interpreting the results.

    Once the testing is complete, it is important to analyze the results and use them to inform future email marketing efforts. If one variation performed significantly better than the other, try to determine why and apply those learnings to future campaigns. If there was no clear winner, test another variable or try a new approach altogether. The goal of A/B testing is to continuously improve the effectiveness of email marketing campaigns and ultimately drive more revenue for the business.

    Best Practices For A/B Testing

    Test One Element At A Time

    One of the most crucial steps in A/B testing is the process of testing one element at a time. This best practice allows marketers to conclusively determine the impact of a single variable on their email marketing campaigns. By isolating one element, such as subject lines, call-to-action buttons, or content length, marketers can accurately analyze its effects without any confounding variables. It is essential to have a clear hypothesis and change only one element at a time to avoid skewing results.

    For instance, testing a subject line and altering the email content at the same time cannot provide an accurate measurement of the individual impact of each change. Testing one element at a time allows marketers to make data-driven decisions, leading to increased engagement and conversion rates. It is vital to ensure sample size and statistical significance to obtain accurate and actionable results.

    Test A Large Enough Sample Size

    When it comes to conducting an A/B test, one of the most significant factors is ensuring that the sample size is large enough. A/B testing involves comparing two versions (version A and version B) of a website or email to determine which one performs better. If the sample size is too small, the results may not be statistically significant, which means that there is a risk of making incorrect conclusions. To avoid this, it is essential to test a large enough sample size so that the results are reliable.

    There are different approaches to determining the sample size required for an A/B test. One commonly used method is to use a statistical significance calculator or a sample size calculator. These tools use statistical algorithms to help you calculate the minimum sample size required to detect a difference of a particular magnitude between version A and version B.

    Another important consideration when determining the sample size is the baseline conversion rate. The conversion rate is the rate at which users take the desired action, such as making a purchase or signing up for a newsletter. If the baseline conversion rate is low, a larger sample size may be required to detect a significant difference between version A and version B.

    It is important to note that there is always a trade-off between the sample size and the duration of the test. The larger the sample size, the longer the test may take to reach statistical significance. Therefore, it is important to choose a sample size that is large enough to ensure reliable results, but not too large that it will take an unnecessarily long time to complete the test.

    Set A Clear Goal

    Before embarking on any A/B testing campaign, it is essential to set a clear goal. The goal should be specific, measurable, achievable, relevant, and time-bound. Without a clear goal, it is impossible to measure the success of the test accurately. A clear goal ensures everyone in the team is pulling in the right direction and that everyone understands what success looks like. It is advisable to focus on the primary goal of the campaign and avoid secondary goals that may dilute the primary goal. Secondary goals are often challenging to track and may provide misleading results.

    Setting a clear goal requires an understanding of the company’s business objectives, target audience, and the stage in the sales funnel the audience is at. This knowledge is essential in ensuring that the A/B test is aligned with the company’s overall strategy and that the target audience’s needs are being met.

    The goal of the A/B testing campaign can differ depending on the objective the company is trying to achieve. For example, a company may want to test the effectiveness of a call-to-action button, or it may want to test the effectiveness of a subject line in an email campaign. In both cases, the goal should be clearly defined and measurable. It is advisable to use SMART (specific, measurable, achievable, relevant, and time-bound) goals when setting the testing objectives.

    When setting a clear goal, it is essential to identify the KPIs that will be used to measure the success of the test. The KPIs should be identified before the test begins and should be based on the goals of the test. KPIs may include open rates, click-through rates, conversion rates, and revenue generated. Setting clear KPIs ensures that there is a clear benchmark against which the test can be compared.

    Test Regularly

    One of the most important practices when it comes to A/B testing email marketing is to test regularly. It’s not enough to perform a single A/B test and then assume that the results will hold true in perpetuity. Instead, regular testing is necessary to ensure that your strategies are aligned with the current preferences of your target audience.

    Testing regularly also allows you to quickly identify changes in consumer behavior and adjust your marketing accordingly. By testing often, you can identify the impact of changes in marketing strategies and assess whether new approaches are likely to achieve the desired results. It also helps to avoid stagnation in your marketing approaches by continually providing clients with new, refreshed content and perspectives.

    It’s essential to establish an A/B testing schedule that provides input to your email marketing strategies consistently. A/B testing can be performed on various criteria, such as the time-of-day for email sends, email deliverability, and sender identification. New strategies continually present themselves, and it is essential to test regularly to make sure that adjustments adhere to consumer interests.

    Another important aspect to keep in mind is the volume of data you collect during each experiment. Regular testing ensures signal consistency by collecting sufficient data to make an informed decision. The sample size needs to be suitable to make sure the A/B test analysis is not subject to bias. Thus testing regularly can help amass large amounts of data, which can facilitate better and more reliable results.

    Additionally, regularly A/B testing Email marketing strategies will also allow you to build a strong baseline for future analysis. By frequently testing various approaches, you can identify a baseline of what works and what doesn’t in marketing campaigns. Over time, this process allows you to refine your marketing strategies to better cater to your target audience’s needs, which, in turn could, impact the outcome of the A/B tests.



    Email marketing remains one of the most effective means of brand promotion and customer engagement. However, with people receiving numerous emails every day, it takes strategic planning to make sure your emails get opened and read. One effective method is A/B testing, which involves comparing two versions of an email to see which one performs better.

    By subjecting different variables to trial and error, the marketer can refine their email content to meet the needs of their target audience. The variables could range from subject line, sender name, call-to-action message, colors, images, and layout, among others. Email marketing using A/B testing has significant benefits, including increased open rate, click-through rate, and conversion rate, among others. By implementing the best practices of A/B testing, companies can enhance their email marketing strategies, improve their customer experience, and achieve their business objectives.

    Future Outlook

    Despite being an essential marketing strategy for businesses of all sizes, email marketing continues to evolve rapidly. With the increasing popularity of smartphones and other mobile devices, many businesses must optimize their email marketing campaigns to reach their target audiences effectively. The application of AI in email marketing has led to the development of more advanced analytics systems that provide businesses with more accurate results than traditional A/B testing methods.

    Future developments are expected to further improve the effectiveness of email marketing campaigns, with AI systems becoming even more advanced at measuring customer behavior and identifying trends. Simultaneously, new and emerging technologies such as wearable technology and virtual reality are likely to transform email marketing in numerous ways, from creating more immersive content to offering new, more innovative ways to segment and target audiences. As with all forms of marketing, staying ahead of the competition and remaining flexible with your approach will be key to success in the rapidly evolving world of email marketing.

    A/B Testing In Email Marketing: FAQ

    1. What Is A/B Testing In Email Marketing?

    A/B testing is a process of experimenting with two different versions of an email campaign to determine which version performs better. This process allows marketers to optimize their campaigns by testing variations in subject lines, images, calls-to-action, and other elements.

    2. Why Is A/B Testing Important In Email Marketing?

    A/B testing helps marketers to identify the best-performing elements of an email campaign and make data-driven decisions about how to optimize future campaigns. It allows them to improve their email marketing strategy and increase the chances of reaching their target audience with the right message.

    3. What Are Some Common Elements To Test In A/B Testing?

    Common elements to test in A/B testing include subject lines, email content, images, calls-to-action, personalized content, and sending time. Testing these elements can help marketers understand which variables have the most significant impact on open rates, click-through rates, and conversion rates.

    4. How Do You Set Up An A/B Test In An Email Campaign?

    To set up an A/B test, marketers need to define the test’s objective, determine the elements to test, create the variations of the email, select the sample size and the test duration, and track the results. Marketers can use A/B testing tools that are available in most email marketing platforms to automate this process.

    5. How Long Should An A/B Test Last?

    The duration of an A/B test depends on the sample size and the test objective. Generally, the test should run long enough to collect sufficient data to make informed decisions. A rule of thumb is to test for at least one week but not longer than two weeks to avoid biases due to changes in the audience’s behavior.

    6. How Can You Use A/B Testing Results To Improve Future Email Campaigns?

    A/B testing results should be analyzed to identify the most effective email elements that contributed to the success of the test. Marketers should use these insights to optimize future campaigns and adjust their overall email marketing strategy. Continually testing email elements and measuring performance can help marketers improve their email engagement and ROI over time.

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    Hanson Cheng

    About the author

    Living in Portugal with my wife and puppies.
    Scaling online businesses and sharing lessons learned on this website and in our email newsletter.

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