Testing email deliverability is critical for any B2B sales team or startup reaching out to potential customers. When your emails don’t reach the inbox, your entire outreach strategy fails—no matter how compelling your message or how qualified your leads are.
Email deliverability determines whether your messages land in the primary inbox, get filtered to spam, or disappear entirely. For startups and small sales teams conducting outreach campaigns, maintaining high deliverability rates directly impacts revenue and growth. This comprehensive guide shows you exactly how to test email deliverability and which tools deliver the most reliable results.
📌 Quick Takeaways:
- Both free and paid tools are available depending on your testing needs and budget
- Email deliverability measures whether emails reach the primary inbox, not just the recipient’s server
- Regular testing prevents deliverability issues before they damage your sender reputation
- The average email deliverability rate is 88.9%—consistently scoring below 85% indicates problems
- Authentication protocols (SPF, DKIM, DMARC) are essential before any deliverability testing
Table of Contents
What Is Email Deliverability?
Email deliverability measures your success rate in getting emails to land in recipients’ primary inboxes, not spam or promotional folders. This metric is essential for B2B sales teams and startups using email outreach to generate leads and drive revenue.
When you test email deliverability, you’re measuring whether your emails pass through spam filters, authentication checks, and reputation screenings to reach your intended audience. High deliverability means your carefully crafted messages actually get seen—low deliverability means wasted effort and missed opportunities.
The Difference Between Delivery and Deliverability
Many people confuse email delivery with deliverability, but they measure different things:
Email Delivery refers to whether an email successfully reaches the recipient’s mail server. If you get no bounce notification, the email was delivered.
Email Deliverability goes further by measuring whether that email landed in the primary inbox versus spam, promotions, or other folders. An email can be “delivered” but still fail to reach the inbox where recipients will actually see it.
For cold email campaigns targeting startup founders or B2B decision-makers, deliverability is what matters. Your message needs to appear in the primary inbox to generate responses and meetings.
Key Factors Affecting Email Deliverability
Several elements determine whether your emails reach the inbox when you test email deliverability:
Sender Reputation: Email providers assign reputation scores based on your sending history, recipient engagement, spam complaints, and bounce rates. Poor reputation means emails go straight to spam.
Authentication Protocols: SPF, DKIM, and DMARC records verify that you’re authorized to send from your domain. Missing or misconfigured authentication kills deliverability.
Email Content Quality: Spam filters analyze subject lines, body text, links, and images. Content that triggers spam signals—excessive capitalization, misleading claims, suspicious links—reduces deliverability.
Recipient Engagement: How recipients interact with your emails influences future deliverability. High open rates, replies, and forwards signal valuable content. Deletes, spam reports, and ignores damage your reputation.
Bounce Rates: High bounce rates from invalid email addresses tell providers you’re not maintaining a clean list, which hurts deliverability across all recipients.
ISP Policies: Each email provider (Gmail, Outlook, Yahoo) has unique filtering systems and spam prevention rules that affect whether your emails reach the inbox.
How to Measure Email Deliverability
Email deliverability is expressed as a percentage: the number of emails that successfully land in primary inboxes divided by total emails sent (excluding bounces).
Deliverability Rate = (Emails in Primary Inbox / Total Sent) × 100
The industry average deliverability rate is approximately 88.9%. If you’re consistently testing below 85%, your sender reputation and email practices need immediate attention.
Key metrics to track when you test email deliverability:
- Inbox Placement Rate: Percentage reaching primary inbox
- Spam Folder Rate: Percentage filtered to spam
- Promotions Tab Rate: Percentage landing in Gmail’s Promotions tab
- Missing Rate: Percentage that disappears entirely (typically blocked)
Why Deliverability Matters for Startups
For startups and small B2B sales teams, email deliverability directly impacts your ability to generate pipeline and revenue. When you’re reaching out to recently funded startups or potential customers with limited marketing budgets, email is often your primary channel.
Poor deliverability means:
- Your cold email campaigns produce no responses
- Potential customers never see your value proposition
- You waste time crafting messages that go unseen
- Your sales team struggles to book meetings
- Revenue growth stalls despite solid outreach effort
Testing and maintaining high deliverability ensures your startup’s growth engine keeps running.
How to Test Email Deliverability
Regular deliverability testing helps you catch issues before they damage your sender reputation and tank your campaign performance. Here’s when and how to test effectively.
When You Should Test Deliverability
Before Launching New Campaigns: Always test deliverability before sending to your full list. A deliverability check on a small sample (50-100 emails) reveals potential issues before they affect thousands of recipients.
After Major Email Changes: Made updates to your email template, changed sending domains, or modified your email infrastructure? Test immediately. Even small changes can impact how email providers filter your messages.
When Engagement Drops: If you notice declining open rates, fewer responses, or increased bounces, test your deliverability. These symptoms often indicate your emails are being filtered or blocked.
Monthly for Active Campaigns: If you’re running ongoing outreach campaigns, test deliverability monthly. Email provider algorithms and filtering rules change regularly, and proactive testing helps you adapt.
Industry Benchmark Checks: Test quarterly to compare your deliverability against the industry average of 88.9%. Consistently scoring below 85% requires immediate action to improve your email domain reputation.
After Warming Up New Domains: When you warm up a new email account, test deliverability throughout the process to ensure you’re building positive sender reputation.
Email Deliverability Testing Best Practices
Follow these practices to get accurate, actionable results when you test email deliverability:
Create Dedicated Test Accounts: Set up new email accounts specifically for testing across multiple providers (Gmail, Outlook, Yahoo, etc.). Using fresh accounts prevents your existing sender reputation from skewing results.
Test Across Multiple Providers: Different email services use different filtering algorithms. Test your emails on Gmail, Outlook, Yahoo, Apple Mail, and any other platforms your target audience uses.
Use Real Email Content: Test with actual email templates and content you plan to send, not placeholder text. Spam filters analyze specific content elements, so realistic testing produces accurate results.
Check Authentication First: Before testing deliverability, verify your SPF, DKIM, and DMARC records are properly configured. Missing authentication will automatically fail most deliverability tests.
Audit Content for Spam Triggers: Review your email copy for common spam signals before testing:
- Excessive capitalization or exclamation marks
- Phrases like “Act now!” or “Limited time!”
- Suspicious or shortened URLs
- Large images with minimal text
- Misleading subject lines
Monitor Key Engagement Metrics: Track these metrics alongside deliverability testing:
- Open rate (aim for 30%+ for B2B cold email)
- Click-through rate
- Reply rate (5-10% is strong for cold outreach)
- Bounce rate (keep below 2%)
- Spam complaint rate (must stay under 0.1%)
Test from Clean Email Lists: Only test with verified, opted-in email addresses or properly sourced B2B lead lists. Testing with purchased or scraped lists produces misleading results and damages your reputation.
Space Out Your Tests: Don’t send hundreds of test emails at once. Space them out over several hours or days to simulate realistic sending patterns and avoid triggering rate limits.
Document Your Results: Keep records of your deliverability test results over time. Tracking trends helps you identify what’s working and quickly spot emerging issues.
Remember that open rates vary significantly by email type. Marketing emails averaging 30% open rates are performing well, while transactional emails (order confirmations, password resets) typically see 80-85% open rates because recipients expect them.
10 Best Email Deliverability Testing Tools
The right testing tool provides insights into inbox placement, spam scoring, authentication status, and actionable recommendations for improvement. Here are the best options for startups and B2B sales teams in 2025.
1. MailerCheck
MailerCheck offers comprehensive deliverability testing with bulk email verification, real-time API access, and detailed analytical reports. The platform integrates directly with popular email service providers, making it easy to verify large lists before sending campaigns.
Key Features:
- Bulk and real-time email verification
- Detailed deliverability reports
- Blacklist monitoring
- DMARC reporting
- ESP integration
Best For: Marketing teams and startups sending high volumes who need both verification and deliverability testing in one platform.
Pricing: Free tier includes 200 email checks, 2 blacklist monitors, and 1 DMARC domain. Paid plans start at $10 for 1,000 credits, with reputation monitoring from $125/month.
Pros: Comprehensive feature set, strong ESP integrations, affordable entry point
Cons: DMARC reporting and advanced monitoring require paid subscription
2. Litmus
Litmus combines email design, testing, and deliverability into a single platform. Beyond testing inbox placement, Litmus provides a visual email builder, rendering previews across 100+ email clients, and a pre-send deliverability checklist.
Key Features:
- Spam filter testing
- Email rendering previews
- Deliverability checklist
- Visual email builder
- Collaborative workspace for teams
Best For: Teams that need design tools alongside deliverability testing, especially those creating visually complex emails.
Pricing: Plans start at $99/month
Pros: All-in-one platform for design and testing, excellent collaboration features, user-friendly interface
Cons: No email verification service, higher price point than testing-only tools
3. GlockApps
GlockApps specializes in automated inbox placement testing, blacklist monitoring, and DMARC analysis. The platform excels at testing transactional email campaigns and provides clear, actionable recommendations for improving deliverability.
Key Features:
- Automated inbox placement tests
- Blacklist monitoring
- DMARC analysis and reporting
- Detailed improvement recommendations
- Flexible pay-per-test pricing
Best For: Startups and developers sending transactional emails who need flexible, pay-as-you-go testing.
Pricing: 3 free spam tests for trial, paid bundles start at $79/month
Pros: Flexible pricing model, excellent instructions for fixes, strong automation features
Cons: No email verification functionality
4. SpamCheck by Postmark
SpamCheck is a free tool that instantly analyzes your email content and assigns a spam score. While basic compared to paid alternatives, it’s excellent for quick checks and identifying obvious deliverability issues.
Key Features:
- Instant spam scoring
- Content analysis
- Identifies common spam triggers
- No account required
- Completely free
Best For: Quick spot checks, budget-conscious startups, identifying basic content issues before sending.
Pricing: Free
Pros: Simple to use, instant results, no registration needed, free
Cons: Basic functionality, limited insights, doesn’t test actual inbox placement
5. Validity Everset
Validity Everset is an enterprise-grade platform offering advanced features like send-time optimization, competitor intelligence, and access to deliverability consultants. Beyond testing, it provides strategic guidance for improving email program performance.
Key Features:
- Send-time optimization
- Competitive intelligence
- Subject line testing
- Engagement analytics
- Deliverability consultant access
Best For: Established companies with substantial email volumes and budgets who need strategic consulting alongside testing.
Pricing: Enterprise plans start at $525/month, with a basic plan at $20/month
Pros: Advanced features unavailable elsewhere, expert consultant access, comprehensive analytics
Cons: Expensive, some features have limited applicability for smaller teams
6. Netcore Email API
Netcore Email API (formerly Pepipost) is a cloud-based email delivery engine built for transactional and triggered emails. It emphasizes reliability and speed, ensuring high deliverability rates for time-sensitive messages like password resets and order confirmations.
Key Features:
- High-speed email delivery
- Real-time analytics
- API integration
- Automated deliverability optimization
- Dedicated IP addresses
Best For: SaaS startups and apps sending transactional emails at scale.
Pricing: Tiered based on volume, starting at $17.50 for 150,000 emails/month
Pros: Excellent for transactional email, reliable delivery engine, scales with growth
Cons: Less suited for marketing email campaigns
7. SMTP2GO
SMTP2GO provides SMTP relay services with built-in deliverability features. The platform handles email sending while providing detailed analytics, automated domain authentication, and spam prevention tools.
Key Features:
- SMTP relay service
- Automated SPF/DKIM setup
- Detailed interaction analytics
- Real-time delivery monitoring
- API and SMTP access
Best For: Teams needing a reliable SMTP service with deliverability monitoring for high-volume sending.
Pricing: Starter plan at $15/month for 40,000 emails, scales with volume
Pros: Reliable infrastructure, automated authentication, comprehensive analytics
Cons: More expensive at higher volumes compared to bulk email providers
8. Constant Contact
Constant Contact is primarily known as an email marketing platform, but includes robust deliverability features essential for small businesses. It offers real-time reputation monitoring, automated list cleaning, and feedback analysis.
Key Features:
- Real-time account reputation monitoring
- Automated list cleaning
- Spam complaint analysis
- Email templates
- Marketing automation
Best For: Small businesses and nonprofits needing an all-in-one email marketing platform with built-in deliverability protection.
Pricing: Lite plan starts at $12/month
Pros: Affordable, easy to use, includes marketing tools, automatic list maintenance
Cons: Limited advanced deliverability testing features compared to specialized tools
9. Folderly
Folderly uses AI to optimize email deliverability by analyzing inbox placement, domain health, and content scoring. It provides a domain score that gives a clear overview of your email performance and integrates with most major email service providers.
Key Features:
- AI-driven deliverability optimization
- Rapid domain health assessment
- Inbox placement testing
- Domain reputation scoring
- Claims 100% deliverability rate
Best For: Teams serious about maximizing deliverability who want AI-powered optimization.
Pricing: Plans start at $200 per mailbox per month
Pros: Advanced AI optimization, comprehensive solution, wide ESP compatibility
Cons: Premium pricing, may be overkill for small campaigns
10. MXToolbox
MXToolbox is a comprehensive suite covering multiple aspects of email infrastructure and deliverability. With tools for blacklist checking, DMARC lookup, spam analysis, and DNS monitoring, it’s ideal for technical teams managing their own email infrastructure.
Key Features:
- Blacklist monitoring across 100+ lists
- DMARC, SPF, DKIM lookup and validation
- Spam analyzer
- DNS monitoring
- Email header analysis
Best For: Technical teams and IT professionals who need deep infrastructure monitoring alongside deliverability testing.
Pricing: Free blacklist monitoring available, subscription plans start at $129/month for advanced features
Pros: Comprehensive toolset, strong technical depth, excellent for infrastructure monitoring
Cons: Can be complex for non-technical users, higher price for full features
💡 Pro Tip: Start with free tools like SpamCheck to catch obvious issues, then invest in paid platforms like MailerCheck or GlockApps as your email volume grows. For teams lacking technical expertise, consider Growth List’s DFY service, which handles deliverability testing and optimization as part of full campaign management.
Why Testing Email Deliverability Is Critical
Regular deliverability testing isn’t optional for startups and B2B sales teams—it’s fundamental to email success. Here’s why it matters so much:
Protect Your Sender Reputation
Your sender reputation functions like a credit score for email. Email providers track how recipients interact with your messages—opens, replies, spam reports, and deletes—to determine whether future emails reach the inbox or get filtered.
A single campaign to the wrong audience or with poorly configured authentication can damage reputation that took months to build. Regular testing helps you:
- Catch reputation issues before they spiral
- Identify which emails trigger spam filters
- Monitor your standing across different email providers
- Make adjustments before significant damage occurs
Think of deliverability testing as preventive maintenance for your email infrastructure. Small issues caught early are far easier to fix than catastrophic reputation damage that requires weeks or months to repair.
Maximize Campaign ROI
Email outreach, particularly for startups with limited budgets, offers exceptional ROI—but only when your messages reach the inbox. Every email that lands in spam represents wasted effort, lost opportunity, and reduced revenue potential.
Consider the math: If you’re sending 1,000 cold emails per week to qualified startup leads, and poor deliverability means only 70% reach the inbox instead of 90%, you’re losing 200 potential touchpoints every week. Over a year, that’s 10,400 missed opportunities.
Testing deliverability ensures you’re getting maximum return on the time and resources invested in email campaigns. When you identify and fix deliverability issues, you immediately improve the efficiency of your entire sales process.
Maintain List Health
Regular deliverability testing helps you maintain a clean, healthy email list by identifying problematic addresses and domains. High bounce rates from invalid addresses damage your sender reputation across all recipients.
Deliverability tools identify:
- Invalid or non-existent email addresses
- Spam traps planted by email providers
- Addresses with full inboxes
- Domains with strict filtering policies
Removing problematic addresses before sending keeps your bounce rate low, your reputation high, and your campaigns performing at their best. For B2B teams buying lead lists, deliverability testing is essential to verify list quality before committing to large purchases.
Adapt to Email Provider Changes
Email providers constantly update their spam filtering algorithms, authentication requirements, and deliverability policies. What worked perfectly six months ago might trigger spam filters today.
Gmail, Outlook, and other major providers regularly adjust:
- Machine learning algorithms that detect spam patterns
- Requirements for domain authentication
- Engagement thresholds for inbox placement
- Bulk sender policies
Regular testing helps you stay ahead of these changes. When a new Gmail update changes how they filter emails, you’ll catch the impact in your testing before it devastates your campaigns.
This adaptive approach is especially critical for startups in competitive spaces where email is your primary customer acquisition channel. Miss a major deliverability shift, and your pipeline can dry up in weeks.
Start Testing Your Email Deliverability Today
Email deliverability directly determines whether your outreach efforts generate pipeline or disappear into spam folders. For startups and small B2B sales teams, where every lead matters and budgets are tight, maintaining high deliverability is essential for sustainable growth.
Testing your email deliverability isn’t a one-time task—it’s an ongoing process that protects your sender reputation, maximizes campaign ROI, and ensures your carefully crafted messages actually reach your target audience. Whether you’re conducting cold outreach to recently funded startups or nurturing existing leads, deliverability testing should be a regular part of your email strategy.
Key steps to get started:
- Verify your domain authentication is properly configured (SPF, DKIM, DMARC)
- Choose a testing tool appropriate for your needs and budget
- Test before launching new campaigns or making major changes
- Monitor key metrics monthly and adjust based on results
- Clean your email lists regularly to maintain healthy bounce rates
Start with free tools like SpamCheck for basic content analysis, then graduate to comprehensive platforms like MailerCheck or GlockApps as your email volume grows. If managing deliverability testing feels overwhelming or you lack technical expertise, consider services that handle the entire process for you.
Want to skip the technical complexity? Growth List’s DFY service handles everything from domain authentication and deliverability testing to full campaign management, so you can focus on closing deals instead of troubleshooting email infrastructure.
The bottom line: Email deliverability testing is not optional. Your startup’s growth, your team’s efficiency, and your campaign success all depend on emails actually reaching the inbox. Start testing today and protect the most important channel in your sales and marketing stack.
References
B2B Lead Generation Toolsdeliverability/
https://www.sendpost.io/blog/transactional-emails
Email Deliverability Guide by Mailchimp
How to Test Email Deliverability
Test Email Deliverability Best Practices
Best Email Deliverability Tools
The Importance of Testing Email Address Deliverability
Transactional Email Best Practices
Email Authentication Protocols (SPF, DKIM, DMARC)
Why Emails Bounce and How to Fix It