Marketing

The $25,000 Subject Line: Why A/B Testing Isn’t Optional Anymore

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We tested two subject lines.

One had a question mark. One didn’t.

That tiny punctuation mark drove a 37% higher open rate and helped generate over $25,000 more in revenue.

And no—this isn’t one of those marketing tall tales. It happened. All because we were curious enough to test.

A/B Testing Isn’t About Being Clever. It’s About Being Curious.

Let’s be honest: email marketing advice is everywhere. Subject line hacks, emoji rules, send-time magic… you’ve heard it all.

But the real secret? Testing. And not just once. Constantly.

Because the difference between a good campaign and a great one often comes down to a single, small choice. The kind of thing you’d never notice unless you were looking for it. Like whether you used a period or a question mark.

What Can You Test? Honestly, Everything.

Here are just a few of the things we test regularly:

  • Subject lines (yes, even the punctuation)
  • Preview text
  • Call-to-action copy
  • Image vs. no image
  • Short vs. long body content
  • Button color and placement
  • Time of day and day of week

The goal isn’t to test for testing’s sake. It’s to learn what your audience actually responds to. Because every time you test something, you’re collecting intel. And that intel makes your next email better.

Small Change. Big Impact.

We once tested an email with a single sentence removed from the opening paragraph. That’s it. No redesign. No new copy. Just a cleaner intro.

Clickthroughs jumped by 19%.

That’s the power of iteration. You don’t have to overhaul your content. You just have to start asking questions.

Be Smart About It

Testing isn’t guessing. It’s measured and intentional. Here’s how we keep our tests clean:

  • Test one variable at a time. Change too much, and you’ll never know what actually made the difference.
  • Use a big enough sample. You need enough volume to trust the results.
  • Let it run. Don’t stop the test early just because one version is in the lead.
  • Look for trends. One test is good. A pattern is better.

Testing Is a Mindset

The best-performing brands aren’t always the flashiest. They’re the ones that are always improving. Always tweaking. Always curious.

They test because they want to learn. They learn because they want to connect. And they connect because they know what works—because they found out firsthand.

TLDR: Don’t Guess. Test.

Your gut might be good, but your data is better.

If you want better results from your emails, start testing the little things. That one sentence. That one image. That one subject line.

Because sometimes, a single character can change the outcome of a campaign.

And if you’re not sure where to start? You know where to find us.