How to Perform A/B Testing with Email Marketing

Email marketing is one of the most effective digital marketing channels, but sending out emails without understanding what works best can lead to missed opportunities. A/B testing, also known as split testing, is a data-driven approach to optimising email marketing campaigns by comparing different variations to determine which one performs better. 

When done correctly, A/B testing helps improve open rates, click-through rates, and conversions by identifying what resonates most with your audience.

In this guide, we’ll explore the essentials of A/B testing in email marketing, including what to test, how to set up experiments, common mistakes to avoid, and the best A/B testing resources available for running successful tests.

What Is A/B Testing in Email Marketing?

A/B testing in email marketing involves sending two variations of an email to different segments of your audience to determine which version performs better. The goal is to make data-driven decisions instead of relying on guesswork. By changing a single element, such as the subject line, call-to-action (CTA), or design, marketers can measure what influences user engagement and conversions.

How A/B Testing Works

• Choose a single variable to test (e.g., subject line, CTA, images).
• Split your audience into two random, equal segments.
• Send Version A (control) to one group and Version B (variation) to another.
• Analyse key performance metrics, such as open rates, click-through rates, and conversions.
• Apply the insights to future email campaigns for better results.

A/B testing removes assumptions from your marketing strategy and helps create emails that are more likely to drive engagement and revenue.

What Can You A/B Test in Your Emails?

To get the most out of A/B testing, focus on elements that directly impact user engagement. Here are some key components to experiment with:

Subject Lines

Your subject line is the first thing recipients see and significantly affects open rates. Testing different styles can help determine what grabs attention.

• Question vs. statement (e.g., “Are You Missing Out on This Deal?” vs. “Exclusive Offer Inside!”)
• Short vs. long subject lines (e.g., “Flash Sale Today!” vs. “Don’t Miss Our Biggest Sale of the Season—Limited Time Only!”)
• Personalisation (e.g., “Hey [Name], Special Offer Just for You!” vs. a generic subject line)

Call-to-Action (CTA) Buttons

Your CTA is what encourages subscribers to take action. Testing different variations can improve click-through rates.

• Wording (e.g., “Get Your Deal” vs. “Claim Your Discount”)
• Placement (e.g., CTA at the top vs. CTA at the bottom of the email)
• Colour & design (e.g., red button vs. blue button, large vs. small buttons)

Email Content & Design

The overall look and feel of your email can impact engagement. Experiment with:

• Text-based vs. image-heavy emails
• Different layouts (e.g., single-column vs. multi-column)
• Long-form vs. short-form emails

Send Times & Frequency

Timing can play a big role in engagement. A/B testing can reveal when your audience is most active.

• Morning vs. evening emails
• Weekday vs. weekend emails
• Weekly vs. bi-weekly emails

How to Set Up an A/B Test for Email Marketing

Once you decide what to test, follow these steps to set up an effective A/B test:

Step 1: Choose Your Variable

To get meaningful insights, only test one element at a time. If you change multiple elements, it becomes difficult to determine what caused the results. For example, if you’re testing subject lines, both emails should have the same content, CTA, and design.

Step 2: Split Your Audience

Divide your email list into two equal, random segments. The sample size should be large enough to produce statistically significant results. If your list is too small, the findings may not be reliable.

Step 3: Create Two Versions of Your Email

• Version A (Control): The original email without any changes.
• Version B (Variation): The email with a single modified element (e.g., a different subject line or CTA).

Example:

• Version A: “Limited-Time Offer – 20% Off!”
• Version B: “Flash Sale: Save 20% Today Only!”

Step 4: Send & Monitor Performance

Use an email marketing platform such as Mailchimp, HubSpot, or Constant Contact to track key performance metrics, including:

• Open rates (for subject line tests)
• Click-through rates (CTR) (for CTA and content tests)
• Conversions (for sales-focused campaigns)

Step 5: Analyse Results & Apply Insights

Once the test has run for a sufficient period, review the data and determine whether the differences are statistically significant. If the variation performs better, apply the winning version to future campaigns.

Common A/B Testing Mistakes to Avoid

While A/B testing can be powerful, many marketers fall into common traps. Here’s how to avoid them:

Testing Too Many Variables at Once

Changing multiple elements (e.g., subject line, CTA, and design) in one test makes it impossible to determine which change impacted the results. Stick to one variable per test.

Ending the Test Too Early

Some marketers stop tests after a few hours, but trends can shift over time. Allow your test to run at least 24-72 hours to collect enough data for a reliable conclusion.

Not Considering Audience Segments

Different segments of your audience may respond differently. Consider running separate tests for new vs. returning customers or different demographics.

Tools to Help You Run A/B Tests in Email Marketing

Several email marketing platforms offer built-in A/B testing features to streamline the process:

• Mailchimp – A/B testing for subject lines, content, and send times.
• HubSpot – Advanced testing with real-time analytics.
• Constant Contact – User-friendly A/B testing for small businesses.
• Klaviyo – Ideal for e-commerce brands with deep analytics.

Try Constant Contact’s A/B Testing Tool for Better Email Performance

As a solution provider and authorized local expert, Constant Contact’s A/B testing tool is a valuable resource for optimizing email marketing campaigns. 

To see how it can improve your email marketing strategy, try it out by visiting constantcontact.com/igv.

Start A/B Testing Today

A/B testing is a critical strategy for optimising email marketing performance. By continuously testing subject lines, CTAs, email design, and send times, you can refine your campaigns to drive better engagement and conversions.

Start small, track your results, and apply insights to future campaigns. Ready to improve your email marketing results? Contact IGV and speak with the experts today to start strategizing!