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An Easy Guide to A/B Testing Email Marketing Campaigns

Email marketing is a great way to connect with your audience and promote your product or service. However, it can be difficult to know which approach will work best for your business. That’s where A/B testing your email marketing campaigns comes in!

Thorough A/B testing allows you to learn your subscribers’ preferences and deliver the best email campaigns optimized for results. Plus, you can use the results to guide your marketing team, eliminate opinion-based decisions, and grow your brand more effectively.

In this guide, we’ll explore how to improve your A/B testing strategy and catch the eyes (and dollars 💸) of your target audience.

Are you new to email marketing? Learn more by reading our guide on “How to Get Started in Email Marketing.”

What is A/B Testing, and How Does it Work?

Email A/B testing, sometimes called split testing, refers to experimenting with different email variations to determine what your subscribers respond to the best.

When you run A/B tests, you send two versions of one email to similarly-sized sample groups from your email subscribers list.

Then, you measure which version sees the most opens, click-throughs, and sales in your test batch. The winning version goes out to the rest of your subscriber list, where it hopefully collects eyeballs and drives conversions.

The goal of A/B split testing is to evaluate and compare changes to a single variable to drive more clicks and conversions. 

Over time, you can test almost every element, from subject lines to “From” names to call-to-action (CTA) buttons. As you perform more tests and compile your subscriber’s preferences, you can build an effective email campaign and drive more growth. Best of all, most modern email marketing tools offer at least basic A/B capabilities, which makes the testing process much more efficient!

Why is AB Testing Email Marketing Campaigns Important?

Nowadays, many marketers skip email A/B testing in their email campaigns. This happens for several reasons, such as not knowing what to test or relying on information generated by other marketers.

Unfortunately for those people, email marketing, like all marketing, requires knowing your audience – not another industry’s audience. 

Ultimately, your brand, products, and subscribers vary even from your competitors, which makes doing your own research vitally important.

A/B split testing allows you to find and capitalize on those differences. It’s one of the fastest, most efficient ways to connect with your audience and deliver them the content they want to engage with.

For most marketers, the results outweigh the cost and effort. For instance, Campaign Monitor found that improving their templates through A/B testing spiked click-throughs by 127% almost overnight. That’s just one metric – imagine how well you’d perform if you were optimized top to bottom!

7 Factors That You Should A/B Test

One benefit – and drawback – of A/B testing is that you can explore how dozens of variables impact your email marketing performance.

On one hand, that allows for unprecedented personalization, on the other, it requires a lot of testing to get right.

Here are seven factors to consider in email split testing.

1. “From” Name

Some marketers swear that what goes in the “From” field is the most important component of email marketing efforts. (Take your friends, for example. No matter what’s in the subject line, your open rates on their emails are probably 100%!)

As an email marketer, you can use your “From” name to build rapport. Tons of factors can impact your open rates based on your business and audience, such as:

  • Altering the level of formality (Mrs. Jones vs. Cecilia)
  • Whether you present as a person or company name (Fantastic Company A vs. Jenny)
  • And even including a greeting (Yo, it’s Jake!)

The key to success with your From field is selecting and sticking with the best version after you tested it.

Using one name, be it yours or your company name, consistently – allows your subscribers to recognize your emails in the future.  

2. Subject Lines

Your subject line is one of your readers’ first points of contact – it shows up right in the inbox. A compelling subject line makes all the difference in your campaign’s open rates.

Subject lines remain one of the most popular focus areas for A/B testing. They are right there “on the surface.” making the most critical impact. If nobody opens your emails, what is in them won’t matter.

Below, we’ll explore a few ways to maximize your email subject line potential.


According to this study, the subscriber’s name is the single most impactful word in a subject line. Dynamically inserting your audiences’ names can add a feeling of connection and boost the open rate by 14%, leading to higher conversions.

For example, instead of saying “15% off sale!” you could say, “Janet, we’re giving you 15% off today!” This personalizes the subject line and gives the gift of savings simultaneously.

Word Order

The word order in email subject lines serves to frontload or backload information. For example, you could tell your audience:

Use this discount code for 15% off today! vs. Get 15% off today with this discount code!

In the second example, you immediately emphasize the reader’s benefit, potentially increasing open rates.

Question vs. Statement

For many people, leaving a question unanswered drives them crazy – use that to your advantage!

Throwing your audience a question inspires them to open your emails and find the answers your email campaign offers. Formats that catch your audience’s attention to keep them reading (and clicking) may start with:

  • Did you know…?
  • Do you want…?
  • Have you heard…?
  • Where can you…?

You can use A/B testing to see which type of questions work best – if at all.

Symbols or Numbers

Using characters like symbols, numbers, and emojis can capture your readers’ attention as they scroll through their inboxes. The key is to use characters that are catchy and relevant to your email.

You also want to avoid using emojis in every email; otherwise, the bright colors and faces lose their novelty.


A recent study found that subject lines perform best around 41 characters or 7 words.

A shorter subject line length offers just enough information to draw readers in. In comparison, long subject lines may remove the “mystery” that draws your email recipients to click.

3. Email Template Layout

The best-performing email layout varies based on your industry, brand, audience, and the email’s purpose. You’ll also want to consider how much content you cram into each email.

Try switching between one- and two-column layouts or adding text over or through images. Use the responses to gauge whether your audience prefers their information quick and condensed or sprawling and easier to read.

Note: When you test layout, keep your content, subject line, and images the same. The goal is to test how your readers respond to rearranging, not changing, information.

4. Copy

The human attention span fell from 12 seconds to 8 seconds between 2000 and 2015. (You can thank smartphones for that!) Reduced attention spans mean that emphasizing great copy in your email body is more important than ever. 

If you can’t concisely and simply explain your point, product, or offer, you’ll struggle to build a successful conversion process and generate revenue.

Fortunately, you can use A/B testing to ascertain which facets of your copywriting work for your audience.


One way to cater to shorter attention spans is by using fewer words. Minimizing language and maximizing value with short-form copy means sharing your story and offers while keeping subscribers’ attention.

However, this varies by demographic. For instance, older generations or industry professionals may prefer long-form copy that details your offer more thoroughly.


Using your subscribers’ names, referencing their location, or even mentioning their company can improve the relevance and lead to more click-throughs.


Your copy’s tone makes a huge difference in how your audience perceives information. 

Incorporating positivity into your email has been found to engage readers’ brains more powerfully, encouraging them to understand – and act on – key messages.

5. Visuals and Images

Research suggests that human brains process imagery 60,000x faster than text. You can capitalize on this information by using images, graphics, and charts to:

  • Drive home your key message;
  • Encourage information absorption;
  • Increase engagement rates.

During the testing phase, you can examine how the type, color, placement, and quality of images drive conversions.  Adding text, moving GIFs, and even the activity level of subjects within the images can all impact engagement.

That said, images aren’t always successful.

Some marketers have reported that images actually decreased engagement rates because images detracted from their content. (Which is why A/B testing is so darn important!)

6. Your Call-to-Action (CTA)

CTAs are one of the most important parts of any email marketing campaign, especially when it comes to your click-through rate.

You can use your CTA to clarify your audience’s next step, such as:

  • Signing up for a webinar;
  • Purchasing a product;
  • Receiving a discount by acting now;
  • Learning more on your blog.

Of course, the tone and type of CTA matter to your audience. And optimizing your design for maximum clicks ensures that you drive as many conversions as possible.

Buttons vs. Hyperlinks

You can generally choose from two basic CTA designs: adding colorful buttons or using hyperlinked texts. For some marketers, “loud” buttons improve click-through rates by catching readers’ attention.

For others, inserting simple text links right into the conversation better caters to a particular audience or product.


We mentioned loud, right?

Colors can affect human mood and reactions. You can use this to influence your audience’s perception, emotion, and action. Then, apply it to your CTA (both buttons and hyperlinks) or build it into your established color palette.


Regardless of your CTA format, you should choose your copy carefully. Specific, action-oriented copy that drives a sense of urgency can increase your click-through rates more than generic text.

For example, switching from “Shop Here” to “Buy Now” probably won’t make a huge difference.

But moving from “Buy Now” to “I’m in, let’s do this!” or “Discover the secret to eternal youth here!” is almost guaranteed to increase your CTR. Don’t be afraid to speak directly to your readers’ desires and experiences!


Placing your CTA  helps direct your readers to take the actions you desire. If you hide a tiny CTA between images, randomly within the copy, or at the bottom of your email, your subscribers will struggle to find out.

However, if you make your CTA loud and place it strategically, you can guide your readers. 

Try embedding your CTA at the beginning of your copy, at the top of your email, or in product text.


Why choose between the top and bottom of your email when you can put in two CTAs? 

For that matter, why limit yourself to buttons or hyperlinks when you can reap the increased click-through rates of both?

7. Delivery Times

While tons of data exists, it’s best to test this metric to see what works for your industry, brand, and subscribers. While you may never achieve 100% open rates, you’ll see more success some days and times than others.

 For example, people may be more likely to buy after lunch when they’re full than before lunch when they’re “hangry”.

This topic could be a separate post, so we wrote one! Check it out if you would like to learn more about the best times to send marketing emails.

Psst... did you know it's easier than ever to build the perfect email campaign with Tailwind? Sign up for a forever-free plan today to begin discovering the power of email and social media combined!

Types of A/B Testing

You can run four basic types of A/B tests. 

Single-Factor A/B Testing

Single-factor A/B testing involves testing just one factor across two variations of your email. (Such as only changing your CTA or subject line.) 

This type of A/B test requires a 50/50 split of your testing group. Using single-factor testing allows you to explore new ideas and gather intel one change at a time. 

As you test more factors, you can build on your database to make more informed decisions in future campaigns.

Multivariate Testing

Multivariable testing refers to testing multiple variables in a single A/B campaign

Generally, you move to multivariable testing once you’ve performed single-factor A/B tests on everything from your subject lines to your CTA. At this point, the goal is to determine the best combination of different elements rather than how a single factor performs. 

These more complicated tests allow you to build on winning elements from simpler prior tests.

The downside is that you can’t be sure if a single factor or multiple factors encouraged which reader behaviors.

Champion vs. Challenger Testing

Champion vs. challenger testing requires a long-term approach to improving the success of your email campaigns.

In this method, you use your winning variations as control groups against new ideas. (In other words, once you’ve found what works, you come back to test new ideas so you don’t fall into a marketing rut.)

Hold-Out Testing

Hold-out testing involves not sending some of your subscribers a particular email at all. Then, you can measure purchase rates to see if your marketing has any impact whatsoever.

Because this method involves a lack of promotion, it’s best performed rarely and in small groups.

8 Tips for Efficient A/B Testing Campaigns

Modern-day email marketing tools make A/B testing simple and quick. But before you dive in on your own, consider these strategic tips to increase your success.

1. Don’t Rely on Someone Else’s Results

Looking at where and how other marketers can provide valuable insights into your own potential. For instance, dozens of studies exist on the “right” way to write your email subject lines.

But ultimately, you’re running your own business and email campaigns with your own subscribers. Not to mention, marketing success varies widely between industries, brands, and demographics.

Running your own tests is crucial to avoid drawing incorrect conclusions from valid but irrelevant results.

2. Prioritize Which Factors to Test First

Picking between testing subject lines, button colors, and email template format isn’t always easy when you have lots of ideas. 

However, especially at first, you’ll want to prioritize the ideas most likely to drive better results with less effort.

To do so, ask yourself how:

  • …big of an impact each change could make;
  • …confident you are the impact will be positive;
  • …easily you can implement each test.

You can use the answers to these questions to rank your ideas in order of priority and improvement potential.  

3. Don’t Test Too Many Factors at Once

The main goal of A/B testing is to figure out how your subscribers respond to various changes in your marketing strategy. Testing too many variables at once removes your ability to determine what changes – if any – your audience prefers.

Plus, it’s often easier to measure the impacts of small or simple changes over large changes. (Think subject line or call-to-action versus template design.)

It’s best to wait on multivariable testing until you’ve compiled a solid database on individual variables. Then, you can start testing combination changes to build the best long-term strategy for your brand.

4. Identify Your Goal

Once you’ve found a factor to test, you’ll need to decide how you’ll measure your success. Open, click-through, and sales rates are all common email metrics. Consider how you want one primary metric to perform during the test (such as increasing conversions by 50%).

5. Form a Constructive Hypothesis

After you have a metric in mind, you can set up a  hypothesis. A simple “If I change X, then Y could happen” will help you think through your strategy. You’ll also avoid wasting time by making changes that aren’t likely to have a major impact.

At the same time, a well-formed hypothesis can encourage you to think outside the box.

6. Pick the Right Sample Size

When you run A/B tests, you pull out a section of your subscribers as your “guinea pigs.” Once you analyze the data from this smaller group, you can send the winning email to your remaining subscribers.

But determining the right sample size can be tricky.

When you have a smaller mailing list, you’ll need to have larger test groups percentage-wise to see substantial results. For instance, if you have only 500 subscribers, you may A/B test your entire list at once. Then, you can use the information to improve future email campaigns.

For brands with lists over 1,000 subscribers, the 80/20 rule can help. In marketing, this rule suggests that focusing on 20% of subscribers will produce 80% of your results.

So, if you have 1,000 subscribers, you’d use 200 of them for testing or two groups of 100 people. Once the data rolls in, you’d send the winner to the other 800 to drive results.  

7. Set the Right Timing Window

Aside from choosing the right sending time, you should carefully manage your testing timing window. Many marketers prefer to conduct A/B testing the same day the winning email goes out.

However, waiting up to 24 hours gives people more time to engage with (or ignore) emails, producing more accurate results.

On the other hand, if you’re dealing with time-sensitive information in a particular email campaign, you may want to send emails sooner.  

8. Don’t Forget to Act on Your Results

The goal of A/B testing is to find out what email marketing habits work best for your subscribers.

If one version performs better than the other, you have a winner.

If neither test version performs better, you’ve learned that that variable – or what you did to it – doesn’t matter to your audience. In A/B testing, even failed or inconclusive data can be valuable for future email campaigns.

Once you’ve gathered enough data on a single variable, it’s time to act on your newfound knowledge. 

While you don’t only have to stick with “winning” combinations (sometimes it’s nice to switch things up), knowing what increases engagement comes in mighty handy.

Key Takeaways for A/B Email Testing

  • A/B testing your email marketing campaigns can make all the difference between failed and successful email marketing campaigns.
  • Start with single factor testing, and keep putting the winner against contenders!  
  • Test everything, and make sure to take note of all the tests performed.
  • Once you’ve found what works, that’s not time to stop A/B testing. The process should be constant and ongoing to keep up with changing behaviors. 


How Long Should A/B Testing Take?

The testing process can be nerve-wracking, but you need to allow for enough to gather clear data on what the most effective strategy was. Most experts say waiting at least a couple of hours to determine which is the winner for most opens, and it can take 12+ hours to determine which is the winner in terms of revenue.

What is the Goal of Email A/B Test Email Marketing?

The entire goal of email a/b testing is to determine which variation of your email campaign garners the best results. This can be a different definition of “best” based on your current business and marketing goals. Are you looking to increase revenue or grow your email list? These will help to determine the success of your a/b testing. 

Are there Tools to Help Automate A/B Email Campaigns?

There are many email marketing tools out there to help you create a successful a/b email campaign, including Tailwind’s Email Marketing!

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Split testing your email marketing sounds intimidating, but it doesn't have to be! This guide teaches you to A/B test every detail of your emails with ease!


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