Guides
How to Set Up A/B Testing in Klaviyo for Better Deliverability
Author :
MailMend Team
January 6, 2026
Your Klaviyo dashboard shows a 32% open rate. Looks decent, right? But what if 60% of those emails are buried in Gmail's Promotions tab, while a variation with a 28% open rate landed 85% in the Primary inbox? You'd be choosing the wrong winner—and losing revenue. The problem: Klaviyo's A/B testing tracks engagement metrics but cannot measure inbox placement. For e-commerce brands serious about deliverability, combining Klaviyo's native testing with specialized tools like Mailmend transforms guesswork into measurable revenue growth.
Key Takeaways
Klaviyo enables A/B testing for up to 4 variations of campaigns and flows, but doesn't track WHERE emails land (Primary inbox vs. Promotions tab)
E-commerce brands using Mailmend's inbox placement technology achieve 50-100% email revenue increases with results visible on Day 1
Dr. Squatch achieved a 112% email revenue increase, 42% open rate improvement, and 67% CTR increase within 24 hours of implementation
For statistically significant results, Klaviyo requires a minimum of 50 recipients per variation, though larger sample sizes are recommended best practice for more reliable data
Apple Mail Privacy Protection pre-fetches emails, making click rates and revenue metrics more reliable than opens for measuring performance
Setup completes in under 5 minutes when integrating deliverability code with Klaviyo templates
Industry benchmarks show 41-44% average open rates for e-commerce according to 2024 Klaviyo benchmarks, though these figures are inflated by Apple's Mail Privacy Protection
Understanding the Power of Klaviyo for A/B Testing Email Deliverability
Klaviyo's platform provides e-commerce brands with powerful split testing capabilities designed to optimize email performance. The system automatically calculates statistical significance and selects winning variations based on open rate, click rate, or placed order rate.
Native Klaviyo A/B Testing Features
Klaviyo's built-in functionality includes:
Campaign and flow testing: Test subject lines, email content, or send times across up to 4 variations
AI-powered subject line generation: Automatically create and test alternative subject lines using machine learning
Winner auto-selection: Platform identifies best-performing variation and sends to remaining recipients
Real-time analytics: Track opens, clicks, conversions, and revenue attribution within campaign dashboard
Deliverability Hub: Monitor bounce rates, spam complaints, and engagement by provider
For basic engagement optimization, these features work well. Subject line tests improve open rates. Content tests boost click-through performance. Send time tests identify when subscribers are most responsive.
Why Deliverability Impacts Revenue in Klaviyo
Here's the critical gap: Klaviyo tracks what happens after emails are delivered, but not where they land. Gmail's algorithms categorize promotional emails into the Promotions tab, dramatically reducing visibility. Emails in Primary inbox appear at the top of recipients' screens. Promotions tab emails require extra clicks to view.
The financial impact is substantial:
Primary inbox emails receive significantly higher engagement than Promotions tab placement
Brands with poor inbox placement see declining open rates despite quality content
Spam folder placement means zero visibility and zero revenue
E-commerce brands miss Black Friday/Cyber Monday revenue targets due to deliverability issues
Without inbox placement tracking, you're optimizing blind. Your "winning" variation might actually be losing if it lands in spam.
The Critical Role of Email Deliverability in E-commerce Performance
Email deliverability determines whether your carefully crafted campaigns reach subscribers at all. For e-commerce brands, the difference between Primary inbox and Promotions tab placement directly impacts revenue.
Consequences of Poor Deliverability
When Gmail's algorithms categorize your emails as promotional:
Reduced visibility: Subscribers must actively navigate to the Promotions tab to see your message
Lower engagement rates: Fewer opens mean fewer clicks, conversions, and revenue
Sender reputation damage: Poor engagement signals inbox providers to filter future emails more aggressively
Wasted marketing spend: You're paying for email sends that generate minimal return
Competitive disadvantage: Brands achieving Primary inbox placement capture attention while your emails go unseen
Traditional deliverability solutions require comprehensive content overhauls, technical infrastructure changes, or domain warming processes spanning weeks or months. These approaches address symptoms but often fail to solve the core problem: Gmail's promotional categorization algorithms.
Measuring Deliverability's Financial Impact
The revenue difference between inbox placements is measurable:
Brands achieving Primary inbox placement see engagement rates 2-3x higher than Promotions tab
Ministry of Supply recorded 27% open rate increase and 30% CTR increase within one business day
Larsson & Jennings experienced 82% open rate increase and 51% CTR increase, with the solution "saving their Black Friday"
For seven-to-eight-figure e-commerce brands, these improvements translate to hundreds of thousands in additional email revenue annually.
Introducing Mailmend: A Unique Approach to Primary Inbox Placement
Mailmend provides algorithmic inbox placement technology that moves promotional emails from Gmail's Promotions tab to the Primary inbox—without changing email content, copy, or design.
How Mailmend's Technology Works
The platform operates through a three-step process:
Inbox placement analysis: Sends client emails to rotating test inboxes to determine current categorization
Promotional threshold identification: Uses proprietary AI to analyze combined factors Gmail uses for tab categorization
Custom code generation: Creates account-specific code that counteracts promotional signals
Unlike traditional deliverability consulting requiring content modifications, Mailmend operates at the technical header level. The custom code embeds into Klaviyo templates through simple drag-and-drop integration.
Key Differentiators and Benefits
What sets Mailmend apart:
Zero content changes: Keep your existing email designs, copy, and promotional messaging
Immediate results: Revenue impact visible on Day 1
Simple setup: Integration completes in under 5 minutes
Klaviyo-specific: Purpose-built for e-commerce brands using Klaviyo's infrastructure
A/B testable: Measure exact performance lift through Klaviyo's native testing features
Revenue guarantee: Partnership model aligns Mailmend's success with client outcomes
For e-commerce brands experiencing declining open rates or Promotions tab issues, Mailmend addresses the root cause rather than requiring comprehensive strategy overhauls. Check out Mailmend's case studies to see documented results from recognized consumer brands.
Setting Up Mailmend for A/B Testing in Your Klaviyo Account
Integrating Mailmend with Klaviyo enables precise measurement of inbox placement impact through controlled split testing.
The 3-Step Mailmend Implementation
Step 1: Book Demo and Receive Custom Code
Schedule demo call with decision-makers present (required for trial access)
Mailmend's team analyzes your current deliverability performance
Proprietary AI generates account-specific custom code calibrated for your Klaviyo account
Timeline: 1 business day after demo
Step 2: Insert Code into Klaviyo Templates
Access your Klaviyo email template editor
Drag and drop the custom code snippet into template HTML
No technical expertise required—simple copy-paste process
Code works across all campaigns using that template
Setup time: Under 5 minutes
Step 3: Enable A/B Testing Within Klaviyo
Create campaign in Klaviyo as normal
Use Klaviyo's A/B test feature to create two variations
Variation A: Standard email (control group)
Variation B: Email with Mailmend code (experimental group)
Keep subject line, content, and send time identical—isolate only the deliverability code variable
Integrating Mailmend with Klaviyo Templates
The integration leverages Klaviyo's template system for seamless deployment:
Template-level implementation: Add code once, applies to all future campaigns using that template
No workflow disruption: Your existing email creation process remains unchanged
Compatible with all Klaviyo features: Works with personalization, segmentation, and automation
Dedicated support: 1-to-1 client representatives manage implementation and ongoing optimization
Unlike deliverability tools requiring complex ESP integrations, Mailmend's approach maintains full control within your Klaviyo account.
Designing Effective A/B Tests for Primary Inbox Placement
Strategic test design determines whether results provide actionable insights or misleading data.
Variant 'A' (Control) vs. Variant 'B' (Mailmend)
For deliverability-focused A/B testing:
Control Group Setup (Variant A):
Standard email template without deliverability code
Represents current inbox placement performance
Serves as baseline for comparison
Experimental Group Setup (Variant B):
Identical email with Mailmend code integrated
Tests impact of improved inbox placement
Isolates deliverability as the only variable
Critical rule: Change only the deliverability code between variations. If you modify subject line, content, images, or send time simultaneously, you cannot attribute performance differences to inbox placement.
Metrics to Track in Your A/B Tests
Klaviyo's analytics dashboard tracks multiple performance indicators:
Primary metrics:
Open rate difference: Direct measure of visibility improvement (note: Apple MPP inflates this metric)
Click-through rate variance: More reliable than opens due to privacy protection features
Revenue attribution: Ultimate measure of business impact—track revenue per recipient for each variation
Placed order rate: Conversion metric showing purchase behavior differences
Supporting metrics:
Engagement over time: Monitor whether Primary inbox placement improves sustained engagement
Unsubscribe rates: Ensure inbox placement doesn't increase opt-outs
Spam complaint rates: Maintain under 0.3% for Gmail deliverability
Test parameters for statistically significant results:
Test size: 40% recommended (20% per variation, 60% receives winner)
Sample size: For statistically significant results, Klaviyo requires a minimum of 50 recipients per variation, though larger sample sizes are recommended best practice for more reliable data
Test duration: 6 hours minimum for opens/clicks, 3-5 days for revenue-based optimization
Statistical significance: Wait for Klaviyo's confidence indicator before declaring winners
Analyzing Your Klaviyo A/B Test Results for Revenue Impact
Raw data requires interpretation to extract actionable insights and measure true business impact.
Interpreting Open and Click Rate Differences
When analyzing test results:
Open rate analysis:
Primary inbox placement typically improves open rates by 21-82% based on documented case studies
Account for Apple MPP inflation—click rates provide more accuracy
Compare against industry benchmarks (41-44% average for e-commerce)
Click-through rate insights:
CTR improvements of 30-67% indicate genuine engagement increases
StickerYou reported 43% CTR increase with Day 1 boost growing to 100% by month one
Higher CTR confirms subscribers are actually seeing and engaging with emails
Statistical significance requirements:
Klaviyo displays confidence levels in real-time
Don't declare winners without "Statistically Significant" indicator
Small lists may show "Inconclusive"—increase sample size or extend test duration
Attributing Revenue to Primary Inbox Placement
Revenue metrics provide the ultimate performance validation:
Revenue per recipient: Divide total revenue by number of emails sent for each variation
Revenue lift calculation: Calculate percentage increase from control to experimental group
Customer lifetime value impact: Track whether improved placement affects repeat purchase rates
ROI measurement: Compare revenue increase against Mailmend investment
Real-world outcomes demonstrate substantial financial impact:
Dr. Squatch achieved 112% email revenue increase within 24 hours
Clevr Blends recorded 21% open rate increase and 63% CTR increase
Amberjack experienced 54% open rate increase and 51% CTR increase
These results exceed typical A/B test improvements, confirming inbox placement as a high-impact optimization lever.
Beyond A/B Testing: Sustaining Deliverability with Mailmend and Klaviyo
Initial test results prove concept, but long-term success requires ongoing optimization and strategic integration.
Ongoing Monitoring and Optimization
Sustainable deliverability requires continuous attention:
Weekly performance reviews: Monitor deliverability metrics in Klaviyo's Benchmarks dashboard
Segment-specific testing: Different customer cohorts may respond differently to inbox placement
Seasonal adjustments: Test performance during peak periods vs. normal volume
Content variation testing: Even with Primary inbox placement, subject lines and content impact performance
Klaviyo's Deliverability Hub provides essential monitoring tools:
Bounce rate tracking: Maintain under 1% for healthy sender reputation
Spam complaint monitoring: Stay below 0.3% threshold
Engagement by provider: Identify if specific inbox providers require attention
Authentication status: Ensure SPF, DKIM, and DMARC remain properly configured
The Mailmend Partnership Model
Unlike transactional software vendors, Mailmend operates on a partnership approach:
Dedicated 1-to-1 representatives: Personal account management for each client
Revenue satisfaction guarantees: Success metrics tied to actual business outcomes
Compliance review: Team examines authentication and regulations before implementation
Continuous optimization: Ongoing code adjustments as Gmail's algorithms evolve
This model ensures your deliverability solution adapts to changing inbox provider requirements rather than becoming obsolete. For brands interested in white-glove deliverability support, explore Mailmend's partnership program.
Why Mailmend Transforms Klaviyo A/B Testing for E-commerce Brands
While Klaviyo provides excellent engagement analytics, it lacks the critical capability to measure inbox placement—the primary factor determining whether subscribers ever see your campaigns.
Mailmend fills this gap by:
Revealing the hidden variable: Track Primary vs. Promotions tab placement that Klaviyo cannot measure
Enabling true deliverability testing: Isolate inbox placement as a testable variable within Klaviyo's A/B framework
Proving revenue impact: Measure exact financial lift from improved placement through Klaviyo's revenue attribution
Maintaining workflow simplicity: Under 5-minute setup with zero disruption to existing processes
Delivering immediate results: Day 1 revenue impact vs. months-long warming periods
The documented results speak clearly: brands achieving 50-100% email revenue increases, with 112% improvements in best cases, demonstrate the financial impact of solving inbox placement.
For e-commerce brands serious about email revenue, combining Klaviyo's powerful marketing automation with Mailmend's inbox placement technology creates competitive advantage. Your competitors using Klaviyo alone are optimizing blind. You'll be optimizing with complete visibility.
Visit Mailmend to learn how custom inbox placement code can transform your Klaviyo campaigns from Promotions tab obscurity to Primary inbox prominence—and turn your A/B testing from guesswork into revenue growth.
Frequently Asked Questions
What is the main benefit of using Mailmend alongside Klaviyo for A/B testing?
Mailmend enables you to measure and optimize the one factor Klaviyo cannot track: inbox placement. While Klaviyo shows engagement metrics (opens, clicks, revenue) after emails are delivered, it doesn't reveal whether emails landed in Primary inbox, Promotions tab, or spam folder. Mailmend's custom code moves emails from Promotions to Primary inbox, and Klaviyo's A/B testing feature lets you measure the exact revenue difference. Brands report 50-100% revenue increases by combining both platforms.
How quickly can e-commerce brands see results from Mailmend's deliverability solution?
Results appear on Day 1. Dr. Squatch achieved 112% revenue increase within 24 hours. Ministry of Supply saw 27% open rate improvement within one business day. Setup completes in under 5 minutes through simple code insertion into Klaviyo templates. Unlike traditional deliverability solutions requiring weeks of domain warming or content overhauls, Mailmend's algorithmic approach delivers immediate inbox placement improvements.
Does Mailmend require any changes to my existing email content or campaigns within Klaviyo?
No. Mailmend operates at the technical header level without modifying email content, copy, subject lines, designs, or images. You keep your existing promotional messaging, creative strategy, and brand voice exactly as-is. The custom code embeds into Klaviyo templates through drag-and-drop integration, and your normal email creation workflow remains unchanged. This differentiates from traditional deliverability consulting that requires comprehensive content strategy modifications.
What types of e-commerce brands are best suited for Mailmend?
Mailmend serves seven-to-eight-figure e-commerce brands across consumer product categories including personal care, apparel, home goods, food & beverage, and lifestyle accessories. The platform integrates exclusively with Klaviyo, so brands must use Klaviyo as their email service provider. Ideal candidates experience declining open rates, Promotions tab placement issues, or want to maximize revenue during critical periods like Black Friday/Cyber Monday. Mailmend serves 500+ businesses with documented results from brands like Dr. Squatch, Sand Cloud, and Caraway Home.
How does Mailmend guarantee revenue satisfaction?
Mailmend operates on a partnership model where customer success directly correlates with their business model. The company offers revenue satisfaction guarantees and assigns dedicated 1-to-1 client representatives to each account for hands-on optimization. Specific guarantee terms require demo consultation. The emphasis on "your success is our success" partnership language suggests alignment of business incentives with client revenue outcomes rather than fixed-fee service models. This approach ensures ongoing optimization as Gmail's algorithms evolve.
