Split Testing in Email Marketing: What to Test First

Split testing in email marketing is one of the fastest ways to improve campaign results—without sending more emails or spending extra budget. For UK SMEs using purchased B2B data, it’s often the key to smarter outreach and better engagement.

Here’s the hard truth: many emails are sent on a hunch, not on evidence. With simple A/B tests, you can find what actually resonates with your audience—and make every email count.

In this post, we’ll explain what to test first, how to do it properly, and what to avoid. Whether you’re an owner, sales director, or marketer, you’ll get practical, tested insight to sharpen your approach and maximise ROI. Let’s turn guessing into growth—one split test at a time.

Why Split Testing Matters

In B2B outreach, each email is a chance—either to spark engagement or to be ignored. That’s why split testing in email marketing pays off:

• Data beats guesswork. Instead of hoping your subject line works, you’ll know it does.

• Small tweaks, big gains. Changing one line or button can lift opens and clicks significantly.

• Better ROI from your data. Testing ensures you don’t waste purchased contacts—you learn from them.

• Crucial in longer B2B cycles. Testing helps refine messaging across multiple touchpoints.

In short: testing isn’t optional—it’s your strategic edge.

Which Elements to Split Test First

Start simple. Test one thing at a time to clearly see what works:

Subject Lines

First impressions matter—test clarity vs curiosity, short vs long, question vs statement.

Sender Name & Preview Text

Does “Iain from Results Driven” pull more opens than the company name? Does the first line tease help?

Email Copy & CTA

Experiment with tone (friendly vs formal), length (brief vs chunky), or CTA phrasing and placement.

Design & Layout

Plain-text emails vs structured formats—does simplicity or visual design win?

Send Time

Test mornings against afternoons, and week-starts vs midweek. Timing affects attention.

Even picking one element to test will give direction for your next send.

How to Run Effective Split Tests

To get meaningful insights, follow a clear process:

Define One Goal

Decide if you’re measuring opens, clicks, or replies—don’t mix objectives.

Test One Variable

Keep one element different per version. If you’re testing the CTA button, keep timing, copy, design constant.

Use a Decent Sample

Test with at least 20–30% of your audience—too small, and results aren’t reliable.

Give It Time

Let your test run for 24–48 hours (or longer if your volume is small) before declaring a winner.

Analyse and Iterate

Log what wins, understand why, and roll that version out. Repeat regularly.

Building this testing habit pays off in sharper campaigns.

Common Pitfalls to Avoid

Even experienced marketers stumble. Watch for these mistakes:

Changing Too Much at Once

You won’t know what worked if you tweak multiple elements simultaneously.

Rushing to Results

Stop early, and your data might mislead. Let tests mature.

Small Samples, Big Assumptions

Tiny groups give tricky results. Ensure your sample size is fair.

Personal Bias

If one version feels “better,” still go with the numbers. Let your audience decide.

Avoid these traps to make testing a reliable part of your strategy.

Why Choose Results Driven Marketing

We do more than supply data—we help you make it work smarter.

• Grounded experience: We draw from real-world UK SME campaigns—not theory.

• Actionable insight: Our guidance focuses on measurable outcomes, not vanity.

• Straightforward support: Practical advice, no jargon.

• Partnership, not form-filling: From messaging to timing, we tailor your approach.

Want help running split tests or tightening your strategy? Contact us—we’d love to help.

Ready to Start Split Testing?

You don’t need fancy tools to begin split testing in email marketing. Just pick one element and learn fast:

1. Choose your test focus—subject line, CTA, or timing.

2. Test it on a meaningful segment.

3. Apply what you learn. Iterate.

Looking for compliant targets to test with? Check out our GDPR‑compliant email lists for smart UK outreach.

Want help designing your next test or reviewing results? Contact us—we’re here to help you turn data into dialogue, and emails into engagements.

Results Driven Marketing
Helping businesses go from bad data to more customers and profits.
Highly targeted B2B marketing lists for direct mail, email, and telemarketing.
📞 0191 406 6399 | 📍 Cobalt Business Exchange, Newcastle
rdmarketing.co.uk