Guides
How to Set Up A/B Testing in Klaviyo to Measure Inbox Placement Improvements
Author :
MailMend Team
December 19, 2025
Your Klaviyo A/B test shows Variation A won with a 32% open rate. But what if 60% of those emails landed in the Promotions tab, while Variation B's 28% open rate came from 85% Primary inbox placement? You just chose the wrong winner. The truth is, Klaviyo cannot track whether your emails land in the Primary inbox, Promotions tab, or spam folder after delivery. For e-commerce brands serious about maximizing email revenue, measuring true inbox placement requires combining Klaviyo's native A/B testing with specialized deliverability technology like Mailmend.
Key Takeaways
Klaviyo's native A/B testing measures engagement metrics (opens, clicks, conversions) but cannot track placement—you need additional tools to know if emails land in Primary vs. Promotions
Paid Klaviyo accounts include 100 monthly inbox tests for email rendering previews, but this shows HOW emails display, not WHERE they land
A/B tests should use a 40% test size (20% per variation) with a minimum 6-hour duration for statistical significance
E-commerce brands using Mailmend's inbox placement technology report 50-100% increases in email revenue through Primary inbox delivery
Understanding Klaviyo's A/B Testing Capabilities for Email Performance
Klaviyo provides native A/B testing for both campaigns and flows, allowing marketers to test subject lines, email content, and send times. The platform automatically sends winning variations based on engagement metrics you select.
Leveraging Klaviyo's Native A/B Testing Features
Setting up an A/B test in Klaviyo involves:
Creating campaign variations: Navigate to Campaigns, create your email, then click "Create A/B test" above the subject line field
Selecting winning metrics: Choose from open rate, click rate, or placed order rate as your success indicator
Configuring test parameters: Set your test size percentage and duration before the winner is automatically sent
AI-powered optimization: Klaviyo offers AI subject line testing that generates variations and tracks statistical significance
The platform tracks statistical significance in real-time, showing confidence levels as results accumulate. This helps prevent premature winner selection based on insufficient data.
Key Metrics for Measuring Email Success
Klaviyo's dashboard displays several performance indicators:
Open rate: Percentage of delivered emails opened by recipients
Click-through rate: Percentage of recipients who clicked links within the email
Placed order rate: Conversion metric showing revenue attribution
Bounce rate: Hard and soft bounces affecting deliverability
Spam complaint rate: Recipients marking your email as spam
However, these metrics only tell you what happened AFTER delivery—not WHERE your emails actually landed within recipients' inboxes.
The Impact of Inbox Placement: Primary vs. Promotions Tab
Gmail's tab system fundamentally changed email marketing. When promotional emails land in the Promotions tab instead of Primary, visibility drops dramatically, and many recipients never see them at all.
Why Primary Tab Placement Matters for E-commerce
The difference between Primary and Promotions tab placement creates measurable business impact:
Visibility: Primary inbox emails appear alongside personal correspondence, receiving immediate attention
Engagement timing: Recipients check Primary tabs constantly throughout the day; Promotions gets periodic batch reviews
Revenue correlation: Higher visibility directly translates to more opens, clicks, and purchases
For e-commerce brands sending promotional campaigns, Black Friday emails, or product launches, Promotions tab placement can mean significantly lower engagement despite successful delivery.
Analyzing the Business Impact of Promotions Tab Delivery
Gmail uses multiple signals to categorize incoming emails:
Promotional language: Words like "sale," "discount," and "limited time" trigger categorization
Image-to-text ratio: Heavy image content signals promotional intent
Sender behavior patterns: High-volume sending and low engagement history
Technical headers: Certain email formatting signals marketing automation
The challenge? Delivery does not equal deliverability. Your emails can successfully "deliver" to Gmail servers while consistently landing in lower-visibility folders—and Klaviyo's standard metrics won't reveal this problem.
Introducing Mailmend: Algorithmic Inbox Placement Technology for Klaviyo
Mailmend provides proprietary algorithmic inbox placement technology designed exclusively for e-commerce brands using Klaviyo. Unlike traditional deliverability solutions requiring content changes or technical overhauls, Mailmend works through custom code that integrates directly with your existing email templates.
How Mailmend Overcomes Gmail's Promotional Threshold
Mailmend's technology operates through a three-step process:
Analysis: Sending client emails to rotating test inboxes to determine current placement patterns
AI Processing: Proprietary algorithms analyze the "promotional threshold"—the combined factors Gmail uses to categorize emails
Custom Code Generation: Account-specific code counteracts promotional categorization signals
This approach addresses inbox placement at the technical level rather than requiring copywriting changes or design modifications.
The 'Zero Changes' Advantage of Mailmend's Technology
What makes Mailmend distinct from traditional deliverability consulting:
No content modifications: Your email copy, offers, and messaging remain unchanged
No design overhauls: Keep your branded templates and visual identity intact
No complex technical setup: Drag-and-drop implementation in under 5 minutes
Immediate testing capability: A/B test Mailmend-enabled emails against standard sends within Klaviyo
This enables brands to maintain aggressive promotional email strategies while avoiding the deliverability penalties typically associated with high-frequency promotional content.
Step-by-Step: Integrating Mailmend Code into Klaviyo Campaigns
Implementation follows a straightforward process designed for marketing teams without technical expertise.
Preparing Your Klaviyo Account for Mailmend Integration
Before integration, ensure your Klaviyo setup meets baseline requirements:
Branded sending domain: Recommended for accounts with 5,000+ profiles
Email authentication: SPF, DKIM, and DMARC records properly configured
Active campaign history: Existing send data helps Mailmend analyze current placement patterns
Decision-maker access: Book a demo with stakeholders present for trial access
Best Practices for Inserting Custom Deliverability Code
The integration process involves:
Demo and analysis: Mailmend's team reviews your current deliverability situation
Custom code generation: AI generates account-specific code calibrated for your Klaviyo setup
Template insertion: Add the code snippet to your Klaviyo email templates via drag-and-drop
Testing setup: Configure A/B tests comparing emails with and without Mailmend code
Results monitoring: Track performance differences through Klaviyo's native analytics
Setup typically completes in less than 5 minutes for the actual code insertion, with dedicated representatives managing optimization.
Designing Effective A/B Tests for Inbox Placement with Mailmend
Proper test design ensures you're measuring real inbox placement impact rather than confounding variables.
Strategic Segmentation for Valid A/B Test Results
When testing inbox placement improvements:
Isolate the variable: Test ONLY the Mailmend code—keep subject lines, content, and send times identical between variations
Use adequate sample sizes: Klaviyo recommends 40% test size (20% per variation) for reliable results
Set appropriate duration: Minimum 6-hour test periods allow Gmail and Outlook to fully process emails
Segment strategically: Consider testing on Gmail-heavy segments first, as Primary vs. Promotions categorization is Gmail-specific
Setting Up Control and Test Variants for Inbox Placement
Create your A/B test structure:
Control Group (Variation A):
Standard email template without Mailmend code
Represents your current inbox placement baseline
Test Group (Variation B):
Identical email with Mailmend code integrated
Measures the lift from improved inbox placement
Document your hypothesis before each test. Example: "Emails with Mailmend code will achieve higher open rates due to improved Primary inbox placement among Gmail recipients."
Measuring Key Performance Indicators (KPIs) for Inbox Placement Success
Beyond standard email metrics, inbox placement testing requires specific KPI focus.
Beyond Open Rates: Tracking Revenue Impact
The metrics that matter most for inbox placement tests:
Open rate differential: Compare variations to quantify visibility improvement
Click-through rate: More reliable than opens due to privacy protection features
Revenue per recipient: Directly ties inbox placement to business outcomes
Conversion rate: Measures purchase behavior, not just engagement
Long-term engagement trends: Track whether improvements sustain over multiple campaigns
Attributing Success: How Mailmend Boosts Your Bottom Line
Mailmend enables precise attribution through Klaviyo's native analytics:
Side-by-side comparison: View exact performance differences between variants
Revenue attribution: See dollar amounts generated by each variation
Engagement segmentation: Identify which subscriber segments respond most strongly
Campaign-level tracking: Monitor performance across multiple sends over time
This data provides concrete ROI evidence for inbox placement investment decisions.
Analyzing A/B Test Results and Optimizing for Continuous Improvement
Test analysis should inform ongoing optimization, not just single-campaign decisions.
Interpreting Your Klaviyo A/B Test Data
When reviewing results:
Check statistical confidence: Klaviyo shows significance levels—wait for adequate confidence before declaring winners
Compare multiple metrics: An open rate winner with lower revenue isn't truly winning
Account for privacy protection: Weight click rates more heavily than open rates when analyzing results
Document findings: Maintain a testing log tracking hypotheses, results, and learnings
From Insights to Action: Optimizing Your Email Deliverability
Apply test learnings systematically:
Roll out winners: Apply successful Mailmend code across all campaigns
Retest periodically: ISP algorithms change—retest winning variations every 90 days
Segment application: Consider whether certain subscriber segments benefit more from inbox placement optimization
Monitor trends: Track month-over-month performance to catch deliverability changes early
Real-World Impact: Success Stories with Mailmend and Klaviyo A/B Testing
E-commerce brands across categories have achieved measurable results through Mailmend's inbox placement technology.
Transforming Deliverability: Documented Revenue Increases
Case studies from recognized consumer brands demonstrate the impact:
Dr. Squatch (personal care):
112% email revenue increase escaping the Promotions tab
42% open rate improvement
67% click-through rate increase
Results visible within 24 hours
Ministry of Supply (apparel):
27% open rate increase
30% CTR increase
Results appearing within one business day
Larsson & Jennings (watches):
82% open rate increase
51% CTR increase
Solution credited with "saving their Black Friday" after data failures caused deliverability problems
Black Friday & Beyond: Seasonal Success Stories
Additional documented outcomes include:
StickerYou: 64% open rate increase and 43% CTR increase, with initial Day 1 boost of 20% growing to 100% increase by month one
Clevr Blends (beverage): 21% open rate increase and 63% CTR increase
Amberjack (footwear): 54% open rate increase and 51% CTR increase
These results demonstrate consistent performance improvement across e-commerce verticals including personal care, apparel, home goods, food & beverage, and accessories.
Ensuring Compliance and Best Practices for Enhanced Inbox Placement
Sustainable inbox placement improvement requires attention to compliance and sender reputation fundamentals.
Mailmend's Approach to Compliance and Data Security
Mailmend operates within established email marketing regulations:
Compliance review: Teams review compliance documentation before implementation
Authentication integrity: Works alongside existing SPF, DKIM, and DMARC configurations
No data exposure: Code operates at the technical level without accessing customer PII
ESP-native operation: Integrates through Klaviyo's standard template system
Maintaining a Healthy Sender Reputation in Klaviyo
Best practices that complement inbox placement optimization:
Monitor key indicators: Track bounce rates, spam complaints, and engagement trends in Klaviyo's deliverability hub
Maintain list hygiene: Remove chronically unengaged subscribers
Use branded sending domains: Especially critical for accounts exceeding 5,000 profiles
Follow authentication protocols: Ensure SPF, DKIM, and DMARC records remain correctly configured
Why Mailmend Transforms Inbox Placement for Klaviyo Users
For e-commerce brands committed to maximizing email revenue, Mailmend offers a fundamentally different approach to deliverability improvement.
The Mailmend Advantage
Immediate results: Unlike gradual reputation-building strategies requiring months of effort, Mailmend delivers Day 1 performance improvements visible in your first A/B test.
Zero workflow disruption: No copywriting changes, design modifications, or complex technical configurations. Your existing email strategy remains intact—Mailmend simply ensures those emails reach Primary inboxes.
Klaviyo-native measurement: Test exact performance lift through Klaviyo's built-in A/B testing, providing concrete ROI data rather than theoretical deliverability promises.
Dedicated support: 1-to-1 client relationships with dedicated representatives managing implementation and ongoing optimization—not self-service tools with support tickets.
Revenue guarantee: Mailmend's partnership model aligns their success with your results, including revenue satisfaction guarantees.
Getting Started
Brands interested in testing inbox placement improvement can book a demo to qualify for trial access. The process involves:
Demo call with decision-makers present
Deliverability analysis of current email performance
Custom code implementation into your Klaviyo account
A/B testing to measure exact lift
For e-commerce brands where email drives significant revenue, the difference between Promotions tab and Primary inbox placement directly impacts the bottom line. Explore Mailmend's case studies to see documented results from brands across consumer product categories.
Frequently Asked Questions
What is the primary benefit of using Mailmend with Klaviyo for A/B testing?
Mailmend enables you to test true inbox placement impact within Klaviyo's native A/B testing framework. While Klaviyo tracks engagement metrics (opens, clicks, conversions), it cannot measure WHERE emails land—Primary inbox versus Promotions tab. By testing emails with and without Mailmend code, you can isolate the revenue impact of improved inbox placement using metrics you already trust.
How quickly can I expect to see results from A/B testing Mailmend's technology in Klaviyo?
Results are typically visible within 24 hours of your first A/B test. Case studies show brands like Dr. Squatch achieving 112% email revenue increases and Ministry of Supply seeing 27% open rate improvements within one business day. The minimum recommended test duration is 6 hours to allow email providers sufficient processing time.
Does Mailmend's solution require any changes to my email content or existing Klaviyo workflows?
No. Mailmend operates through custom code integrated into your email templates—your copywriting, design, offers, and messaging remain completely unchanged. Setup completes in under 5 minutes through drag-and-drop implementation, with no technical expertise required from your team.
What key metrics should I focus on when measuring inbox placement improvements in Klaviyo?
Focus on click-through rate and revenue per recipient as primary indicators. Click rates provide reliable engagement data, while revenue attribution provides the clearest picture of inbox placement impact on business outcomes.
Is Mailmend compatible with other Email Service Providers besides Klaviyo?
Currently, Mailmend's technology is built exclusively for Klaviyo integration. This focus enables deep technical integration with Klaviyo's template system, A/B testing infrastructure, and analytics dashboard. E-commerce brands using other ESPs would need to migrate to Klaviyo to utilize Mailmend's inbox placement technology.
