Getting people to reply to your emails is hard enough. If you’re sending outreach, cold emails, or even simple nurture sequences, you know the pain of dead inboxes and zero engagement. But are your messages actually bad… or is it just the template? That’s where A/B testing comes in.
This guide is for anyone who wants to make their email templates suck less—specifically, folks using Warmuphero. I’ll show you how to set up real A/B tests, avoid the common traps, and actually get useful answers about what works.
Let’s make your emails less ignorable.
Why A/B Test Email Templates Anyway?
Look, guessing what’ll work is a waste of time. People’s inboxes are packed, so small changes can mean the difference between “delete” and reply. But if you’re just swapping out lines without tracking results, you’re flying blind.
A/B testing lets you:
- Find out what actually gets replies, instead of what you think sounds good.
- Stop wasting time on “best practices” that don’t move the needle.
- Build a repeatable way to improve, template by template.
Warmuphero isn’t magic, but it gives you tools to test and measure—so you can stop hoping and start knowing.
Step 1: Get Set Up for A/B Testing
Before you dive into writing variants, make sure you’re set up for a fair test.
What You’ll Need
- A Warmuphero account: (obviously)
- An email list that’s big enough to test: Tiny lists = random results. You’ll want at least a few hundred people.
- Two or more email templates: Keep it simple. Start with A vs B. Don’t test six versions at once.
Pro Tip
Don’t bother testing if you’re sending fewer than 100 emails per version. Randomness will drown out any real difference. If your list is small, test over a longer period or combine similar campaigns.
Step 2: Write Your Email Variants
This is where most people screw up. A/B testing is only useful if your variants are meaningfully different—but not so different that you don’t know what made the difference.
How to Do It Right
- Change one thing at a time. Just the subject line, or just the opening sentence. Not both.
- Make the change obvious. Tiny tweaks like swapping “Hi” for “Hello” won’t move the needle. Try changing the offer, the call to action, or the tone.
- Keep everything else the same. That means sending at the same time, to similar audiences.
Example
-
Template A: Subject: “Quick question about your website”
Body: Friendly, short, asks for a reply. -
Template B: Subject: “Can I help your team with X?”
Body: Slightly more formal, different call to action.
What Not To Do
- Don’t test 10 things at once. If B wins, you won’t know why.
- Don’t obsess over perfect grammar or “best practices.” Test what feels human.
Step 3: Set Up the A/B Test in Warmuphero
Here’s the nuts and bolts. Warmuphero makes this fairly painless, but you’ve got to get the basics right.
Creating Your Campaign
- Log in to Warmuphero.
- Go to “Campaigns” and hit “Create New.”
- Upload your email list. Make sure your CSV is clean—no weird characters, missing emails, or duplicates.
- Choose the “A/B Test” option. If it’s not obvious, look for something like “Split test” or “Template variants.”
Adding Your Variants
- Add Template A and Template B.
- Assign what percentage of your list should get each variant (usually 50/50 to start).
- Double-check the preview—sometimes formatting gets mangled on upload.
Scheduling
- Send at the same time of day for both variants. Weird timing differences can skew results.
- Enable tracking for opens, clicks, and—most importantly—replies. If you only care about replies, ignore the rest.
Pro Tip
If you have multiple sender accounts, rotate them evenly across variants. Otherwise, deliverability quirks can mess with your test.
Step 4: Let the Test Run—And Don’t Touch It
The hardest part: don’t fiddle. Once your test is running, step back and let it do its job.
- Don’t “peek” at early results and call a winner. You need enough data for a real signal.
- Don’t resend to people who didn’t open. That just muddies the waters.
- Ignore open and click rates, unless replies are your goal. Opens are unreliable these days (thanks, Apple Mail Privacy, etc.).
How long should you wait? At least a week, or until you hit 100+ emails per variant. Impatient? Sorry, that’s how you get false positives.
Step 5: Analyze Your Results Honestly
This is where you cut through the B.S. and see what actually worked.
What to Look For
- Reply rate: This is your north star. If Template B got more replies, it’s the winner. Ignore the rest.
- Statistical significance: Don’t get fancy with math, but be skeptical if the difference is tiny (e.g., 5 replies vs 4).
- Patterns in replies: Are you getting better replies, or just more? Quality counts.
What to Ignore
- Open rates: These are unreliable due to email privacy changes.
- Click rates: Only care if your goal is clicks. For outreach, replies matter more.
- Vanity metrics: Don’t get excited about tiny bumps.
If the Results Are Inconclusive
- That happens. Sometimes A/B tests are a draw. That’s still useful—you’ve learned what doesn’t matter.
- Move on to your next idea. Don’t overthink it.
Step 6: Roll Out the Winner (and Keep Testing)
Found a clear winner? Great, but don’t stop there.
- Switch your main template to the winner.
- Plan your next test. Maybe now you test the call to action, the value prop, or even the sign-off.
- Keep a log. Seriously, write down what you’ve tried and what worked. Otherwise, you’ll forget and repeat yourself.
Pro Tip
Iterate, don’t overhaul. Small, steady improvements beat big, risky changes.
A Few Honest Takes
Let’s get real about what works and what’s a waste of time.
What Works
- Testing bold, clear differences. Don’t be shy.
- Short, personal emails. People reply to humans, not robots.
- Following up. One test at a time, but follow-ups matter more than perfect copy.
What Doesn’t
- Obsessing over design. Plain text works best for outreach.
- Chasing open rates. As mentioned, these are a mirage now.
- Overcomplicating the process. If it feels like a science project, you’ll burn out.
What to Ignore
- “Best time to send” hacks. Unless your audience is wildly global, this matters less than people claim.
- AI-generated templates. They sound generic. If you use them, always rewrite in your own voice.
Wrap Up: Keep It Simple, Keep Iterating
A/B testing in Warmuphero isn’t rocket science. You don’t need fancy tools or a stats degree. Just change one thing, test it, see if replies go up, and repeat. Don’t get sucked into endless optimization or trendy hacks—just focus on sending more human emails and learning as you go.
In email, the simplest answer is usually the right one. Test, learn, and move on. That’s how you actually get more replies.