You ever stare at your email draft, the one you spent hours on, and just… guess? You guess that this subject line is the one. You guess people will like that funny GIF. It’s a feeling lots of us who send emails for a living, or for our own business, know all too well. It’s like throwing spaghetti at a wall and hoping some of it is the kind that sticks.
For 2025, we need to stop throwing spaghetti. Your subscribers’ inboxes are crowded places, and getting their attention is a real competition. The good news is there’s a way to turn your guesswork into something a lot more like a science experiment, but without the lab coat. It’s called A/B testing. And it’s not nearly as scary as it sounds. It is basically a method to figure out what your audience actually wants, not what you think they want.
What Even is A/B Testing in Email? The Simple Version
Okay, let’s break this down super simple. A/B testing, sometimes called split testing, is a pretty straightforward idea.
You create two versions of the same email. Let’s call them Version A and Version B.
The trick is, you only change ONE thing between A and B. Just one. Maybe Version A has a blue button and Version B has a green button. Everything else is identical.
Then, you send Version A to a small part of your email list. And Version B goes to another small, similar part.
You wait a bit, see which email got more clicks, or opens, or whatever you’re measuring. The winner is the email you then send to the rest of your big list. That’s it. You let your audience vote with their clicks. It is a method considered to be very effective.
This whole thing, this A/B testing idea it’s basically just a way to stop guessing. It pits two versions of your email against each other in a mini-competition to see which one performs better.
The Big Stuff to Test in Your Emails for 2025
You could test almost anything, which is kind of the problem. If you try to test everything, you’ll get confused and give up. So don’t do that. Normally, it’s best to focus on the things that will give you the biggest bang for your buck.
Subject Lines: The First Thing Anyone Sees
Your subject line is the gatekeeper to your email. If it’s boring or doesn’t grab attention, nothing else inside your email matters because no one will see it.
Question vs. Statement: Try asking a question (“Feeling stuck with your marketing?”) versus making a statement (“A new way to think about marketing”).
Emojis vs. No Emojis: Does a little airplane emoji ✈️ get more people to open your travel email? Or does it look like spam? Only one way to find out.
Personalization: Using the subscriber’s first name is old news. For 2025 think about testing personalized subject lines based on their past buying behavior. Something like “A new pair of boots to go with your jacket, Sarah?”
Call-to-Action (CTA): Getting People to Click
The CTA is the whole point of many emails. You want someone to do something. So, the words and design you use here are really important. It is here that many people fail to get the click.
Button Wording: Test “Buy Now” against “Learn More.” One is aggressive, the other is softer. Which one does your audience prefer? It can tell you a lot about them.
Button vs. Linked Text: Does a big, colorful button get more action than a simple line of hyperlinked text? Generally yes but you should test it for your own people.
Color and Placement: A bright orange button might work for one brand, but a cool blue might be better for another. Also, try putting the CTA at the top versus the bottom of the email.
Content and Design: The Look and Feel
This is about the guts of your email. The words, the pictures, the whole vibe. This is where you can get really creative with your tests.
Tone of Voice: Send one email that’s super professional and another that’s more casual and funny. See which one gets a better response.
Image Use: Does an email with a big, pretty hero image work better than one that’s just plain text? A lot of people are surprised by the results of this test.
Length: Test a super short, get-to-the-point email against a longer one that tells more of a story. There’s no one right answer for all audiences.
How to Actually Run an A/B Test Without Messing It Up
The idea is easy. Doing it right takes a little bit of discipline. Most email service providers, like Mailchimp or ConvertKit, have A/B testing tools built right in, which makes the technical part pretty easy. The strategy is on you.
First, pick one thing. Just one. I’m saying it again because it’s the main rule. If you change the subject line and the main image, you’ll have no idea which change caused the results.
Next, you have to decide on your sample size. Generally you want to send the test to a small percentage of your list, maybe 10% or 20% total (so 5% or 10% for each version).
Then you run the test. Let it go for a few hours, or maybe a day, to give people a chance to open their emails. Your email tool will tell you when it has a “winner” based on opens or clicks.
After a winner is declared, the winning version automatically gets sent to the rest of your subscriber list. The best part is you now have a little piece of information about your audience you didn’t have before. You learned something.
Common Screw-Ups Everyone Makes with A/B Testing
It’s easy to get this wrong, especially when you’re starting out. Don’t worry. Here are some common mistakes to watch out for.
One is testing on too few people. If you only send your test to 50 people, the results won’t mean much. It could just be random chance. You need enough people to make the results trustworthy.
Another mistake is ending the test too soon. Some people check their email first thing in the morning, others check it in the evening. You need to give the test enough time to collect responses from different types of people.
And a really big one is not keeping track of what you learn. The point of A/B testing isn’t just to get a few more clicks on one email. It’s to slowly build a better picture of what your audience responds to over time. Keep a simple spreadsheet of your tests and what won.
Frequently Asked Questions About Email A/B Testing
1. How many people do I need on my list to A/B test?
There’s no magic number, but you need enough for the results to be dependable. If your test groups have fewer than a few hundred people each, the results might not be very reliable. More is always better.
2. How long should I let a test run before picking a winner?
This depends on your audience. A good starting point is 4-6 hours. But if you know your subscribers are slow to open emails, you might extend it to 24 hours. The main thing is to be consistent.
3. Can I test more than two versions at once?
Yes, that’s called multivariate testing. It’s more advanced because you’re testing multiple combinations at once (e.g., two subject lines and two different buttons). It’s best to stick with simple A/B tests until you get the hang of it.
4. What if my test results show no clear winner?
It happens! It might mean the change you made was too small to make a difference. Or it could just mean your audience doesn’t have a strong preference. Just pick one, send it, and test something completely different next time.
5. What is a “good” open rate or click rate to aim for?
This changes wildly by industry. A “good” number is anything that is better than what you got last time. The goal of A/B testing is continuous improvement, not hitting some imaginary number. Focus on beating your own records.
Key Takeaways
A/B testing is just a way to stop guessing and start using real data to make your emails better.
Always, always, always test only one thing at a time. This is the golden rule.
Start by testing the big things that have the most effect, like your subject line and your call-to-action.
Most modern email platforms have built-in tools that make running the actual test very simple.
Don’t just focus on winning a single test. The real goal is to learn about your audience over time. Keep a record of what works and what doesn’t.
