Glossary
Term | Definition |
---|---|
A/B Testing | A method of comparing two versions of an email to see which performs better. |
Click-Through Rate (CTR) | The percentage of recipients who click a link in the email. |
Conversion Rate | The percentage of recipients who complete a desired action, such as making a purchase. |
HubSpot | A marketing and CRM platform used for email campaigns and automation. |
Open Rate | The percentage of email recipients who open a given email. |
Segmentation | Dividing your email list into smaller groups based on specific criteria. |
Statistical Significance | A measure that determines whether the result of a test is likely due to chance or a specific variable. |
Subject Line | The line of text displayed in an inbox that encourages the recipient to open the email. |
Call-to-Action (CTA) | A prompt in the email that encourages the user to take an action such as “Shop Now.” |
Email Variation | A different version of the same email used in an A/B test. |
Table of contents
Introduction: Why A/B Testing Still Dominates Email Strategy
Despite changing privacy rules, algorithm updates, and shifting customer behaviors, one tactic remains irreplaceable in email marketing: A/B testing. Done right, it doesn’t just improve metrics—it uncovers the psychology of your audience.

If you’re using HubSpot, you’re already equipped with one of the most powerful platforms for A/B testing. But tools don’t drive results—strategy does. This guide shows you how to make HubSpot work harder for your email marketing through targeted, statistically sound A/B testing.
The HubSpot Email A/B Testing Framework
1. Define Your Test Objective
Don’t start with a template. Start with a question:
- Do I want to improve open rates?
- Increase CTR?
- Boost revenue per email?
Common Goals & Matching Variables:
Goal | Test Variable |
---|---|
Improve Open Rate | Subject line, sender name |
Increase Click-Through | CTA text, image, button color |
Reduce Unsubscribes | Content tone, email frequency |
Raise Conversion Rate | Offer type, landing page URL |
Start with ONE goal. Make it measurable.
2. Choose One Variable to Test
A/B testing fails when you try to test everything at once. Here are high-impact variables to prioritize:
Element | Examples |
---|---|
Subject Line | Personalized vs. generic |
CTA Button | “Buy Now” vs. “View Offer” |
Email Layout | Image first vs. text first |
Send Time | Morning vs. evening |
Offer Type | Discount vs. free shipping |
Only test one of these at a time per campaign. Document your hypothesis: “If we use a first-person CTA, we expect a higher CTR.”
3. Segment & Randomize Your Audience
Split your audience into random but equal segments. HubSpot allows easy automation here:
- Version A: 50%
- Version B: 50%
- Optional: Send the winning version to the remaining list.
Pro Tip: Ensure both segments have similar list health (e.g., open history, engagement recency) for an accurate comparison.
4. Determine Sample Size & Significance Threshold
HubSpot’s built-in calculator helps, but here’s a quick rule:
- Under 10,000 recipients? Test with 50%, send the winner to the rest.
- Over 10,000? You can test with 10–30% and expand from there.
Aim for 95% confidence level in your results—meaning you’re 95% sure the winning variation didn’t win by chance.
5. Set the Right Duration
Timing can skew results. Let your test run long enough:
Campaign Type | Minimum Test Duration |
---|---|
Flash Sale | 24 hours |
Evergreen Campaign | 3–5 days |
Weekly Newsletter | 48–72 hours |
Use HubSpot’s duration settings to enforce consistency.
6. Track the Right Metrics in HubSpot
Here’s what to track based on your objective:
Metric | When to Use |
---|---|
Open Rate | Testing subject lines or sender names |
CTR | Testing CTAs or images |
Revenue Per Email | Direct sales-oriented emails |
Click-to-Open Rate | Validates email content quality |
HubSpot’s visual reporting helps you monitor trends, not just isolated wins.
7. Analyze Results with Context
Once your test ends, don’t just declare a winner. Ask:
- Was the margin of improvement statistically significant?
- Did this result match previous tests?
- What user behavior did this variation tap into?
Document your results. Add learnings to your email strategy database.
8. Apply and Retest
Winning subject line? Great—test a variant.
Better click-through with button A? Now test its placement or color.
Turn isolated wins into systemic improvements by folding them into your global strategy.
9. Use A/B Testing Across the Funnel
Beyond just marketing emails, test:
- Transactional Emails: Order confirmations, shipping alerts
- Re-engagement Campaigns: Win-back offers, surveys
- Lead Nurturing: Education series, trial extension promos
Every email is an opportunity to learn and optimize.
FAQs: A/B Email Testing in HubSpot
Q1: How long should I run an A/B test?
At least 24 hours for basic tests. For high-stakes campaigns or large segments, run for 3–5 days.
Q2: How do I choose what variable to test?
Start with what aligns to your main metric: subject lines for open rates, CTAs for click-through, and so on.
Q3: What’s the ideal sample size?
Use 10-50% depending on your total list. Larger lists allow smaller samples.
Q4: Can I A/B test multiple variables at once?
Not recommended unless you’re running a multivariate test. Stick to one variable per test for clarity.
Q5: What if my test shows no clear winner?
You may need a larger sample or a more pronounced difference in variables. Try again with sharper contrasts.
Q6: How often should I A/B test?
Continuously. Test something new in every campaign—email subject, design, CTA, or send time.
Final Thoughts
A/B testing isn’t just a technical feature—it’s a mindset. In a competitive email landscape, the brands that win are the ones who test, learn, and improve relentlessly.
HubSpot makes it easy to set up, execute, and analyze tests, but it’s your strategy that turns data into results.
Need help setting up a winning A/B strategy? Blossom Ecom specializes in data-driven email marketing for Shopify and DTC brands. Let’s build your next best campaign.
Need help implementing this?
Let us take the hassle of managing your email marketing channel off your hands. Book a strategy call with our team today and see how we can scale your revenue, customer retention, and lifetime value with tailored strategies. Click here to get started.
Curious about how your Klaviyo is performing?
We’ll audit your account for free. Discover hidden opportunities to boost your revenue, and find out what you’re doing right and what could be done better. Click here to claim your free Klaviyo audit.
Want to see how we’ve helped brands just like yours scale?
Check out our case studies and see the impact for yourself. Click here to explore.
Read Our Other Blogs

How to Craft Email Newsletters That Build Real Brand Loyalty



Top 3 Best eCommerce Content Management Systems of 2025



Email Marketing vs. Social Media: Which One Should Your Brand Focus On?




Not Sure Where to Start?
Let's find the biggest retention opportunities in your business. Get a free Klaviyo audit or retention consultation.

