Recently, a client came to me frustrated. They were sending emails consistently, but something wasn’t clicking. Open rates were flat. Click-throughs were low. They couldn’t figure out what was going wrong or what to do differently.
It’s one of the most common conversations I have with small business owners about email marketing. And the answer is almost always the same: stop guessing and start testing.
That’s where A/B testing comes in. And if you’re not using it, you’re likely leaving a significant amount of results on the table.
What Is A/B Testing and Why Does It Matter?
A/B testing, sometimes called split testing, is a method of comparing two versions of an email to see which one performs better. You take one element of your email, create two versions of it, send each version to a portion of your audience, and use the results to make smarter decisions going forward.
It sounds simple because it is. But the impact can be substantial.
Email marketing already delivers one of the strongest returns of any marketing channel, generating an average of $36 for every $1 spent. But here’s what makes A/B testing so powerful: marketers who regularly A/B test their emails increase their email ROI by 86% compared to those who never test at all, according to research from Litmus. That’s the difference between a good email marketing strategy and a great one.
Despite this, testing remains one of the biggest gaps in most small business email strategies. Many business owners send the same type of email the same way every time and wonder why results have plateaued. The answer isn’t to send more emails. It’s to send smarter ones.
What Can You Actually Test?
Almost every element of your email is testable. Here’s a breakdown of where to focus:
Subject lines. Your subject line is the single most important factor in whether your email gets opened. A/B testing subject lines is the most common starting point for good reason. Try testing a question versus a statement, a short subject line versus a longer one, a straightforward approach versus one that leads with curiosity, or the inclusion of an emoji versus plain text. Research shows that subject lines with an emoji can improve open rates by up to 56%, but this varies by audience, which is exactly why testing matters. What works for one business’s audience may not work for another.
Send times and days. Timing matters more than most people realize. Industry data consistently shows that emails sent between Tuesday and Thursday tend to perform best for B2B audiences, and that the morning window between 9 and 11 AM delivers strong open rates. But your audience may behave differently. A/B testing send times lets your subscribers, not the industry averages, tell you when they’re most receptive.
Email content and layout. Does your audience respond better to short, conversational emails or longer, more detailed ones? Do they engage more with a single focused message or a format with multiple sections? Do they click on buttons or text links? Adding a call to action button instead of a text link alone can increase clicks by up to 28%. Test it and find out what your audience actually prefers.
Calls to action. The words you use in your call to action matter. “Book a free call” versus “Schedule your consultation.” “Learn more” versus “See how it works.” Small wording differences can produce meaningfully different click-through rates. Test phrasing, placement, and format to see what motivates your specific audience to take the next step.
Word choices and tone. Sometimes the difference between an email that resonates and one that falls flat comes down to a single word or phrase. Testing variations in tone, from more casual to more professional, or testing personalized sender names versus a brand name, can reveal a lot. One A/B test by MailerLite found that using a personal sender name resulted in 3.81% more opens. That’s a meaningful lift from one small change.
Personalization. Brands that use personalization in their emails increase email ROI by nearly 260% compared to those who rarely or never personalize, according to Litmus. Even simple personalization, like using the recipient’s first name or tailoring content based on past behavior, can have a significant impact on engagement.
How to Put A/B Testing Into Practice
The good news is that you don’t need a large list or a complicated setup to start A/B testing. Most major email marketing platforms, including Constant Contact, Mailchimp, and Klaviyo, have built-in A/B testing tools that handle the logistics for you. They split your list, send each version, track the results, and show you a clear comparison of open rates, click-through rates, and conversions.
Here’s the approach that works best:
Test one element at a time. If you change the subject line and the send time and the call to action all at once, you won’t know which change made the difference. Isolate one variable per test so your results are clear and actionable.
Give your test enough time and audience to be meaningful. A test sent to 50 people may not produce reliable results. A larger sample size and a sufficient time window will give you data you can actually trust.
Track everything and apply what you learn. A/B testing isn’t a one-time experiment. It’s an ongoing process of getting to know your audience better with every send. The insights stack up over time. Your emails get sharper, more relevant, and more effective the more consistently you test and apply what you learn.
Start small. You don’t need to overhaul your entire email strategy overnight. Pick one element, run your first test, see what you learn, and build from there.
The Bigger Picture
Email marketing remains one of the most powerful tools available to small business owners. As of 2025, nearly 4.5 billion people use email worldwide, and 60% of consumers prefer to be contacted by brands through email. The audience is there. The question is whether your emails are compelling enough to cut through the noise.
A/B testing is how you find out. It’s how you move from sending emails and hoping for the best to sending emails backed by real data about what your audience actually responds to. It’s how you stop guessing and start growing.
Your audience is already telling you what they want. A/B testing is how you learn to listen.
