Free Seed List Tester

Overview

Seed list testing is the most accurate method to measure email deliverability. Unlike content-based spam checkers that only analyze your message, seed testing sends actual emails to real accounts at Gmail, Yahoo, Outlook, and other major providers to see exactly where they land: inbox, spam folder, promotions tab, or blocked entirely.

How Seed List Testing Works

1. Setup: We maintain 20+ real email accounts across all major ISPs
2. Send: Your test email is sent to all seed accounts using your exact configuration
3. Wait: We monitor for delivery (typically 2-5 minutes)
4. Check: IMAP connections verify placement in each account
5. Report: Results show inbox rate, spam rate, and provider breakdown
6. Screenshot (Pro): Capture actual inbox appearance and placement

What Seed Testing Reveals

Seed testing catches issues that content analysis cannot detect:

Sender Reputation Issues

• IP address reputation at each provider
• Domain reputation and historical sending behavior
• Feedback loop complaints affecting filtering
• Engagement rates influencing inbox placement

Authentication Failures

• SPF alignment issues causing failures
• DKIM signature problems or missing signatures
• DMARC policy failures and alignment
• ARC chain validation for forwarded emails

Blocklist Impacts

• Real-time blocklist rejections
• Silent spam folder placement due to listings
• Provider-specific filtering rules
• URL/domain reputation in content

Provider-Specific Filtering

• Gmail Promotions vs Primary tab placement
• Yahoo Bulk folder routing
• Outlook Clutter/Focused inbox sorting
• Apple Mail intelligence filtering

Seed List Coverage by Provider

Gmail / Google Workspace

Our Gmail seeds include consumer accounts (@gmail.com) and business accounts (@googleworkspace). We test across US, EU, and Canadian regions to catch geographic filtering differences. Gmail uses machine learning that varies by region and account age.

Yahoo / AOL (Verizon Media)

Yahoo and AOL share infrastructure under Verizon Media. Our seeds cover both @yahoo.com and @aol.com addresses. Yahoo is particularly strict about sender reputation and authentication - failed tests here often indicate auth problems.

Outlook / Hotmail / Office 365

Microsoft email includes consumer accounts (@outlook.com, @hotmail.com, @live.com) and business Office 365 accounts. Their SmartScreen filter is aggressive about blocklists and sender reputation. We test both personal and business account types.

Apple Mail / iCloud

Apple Mail Protection (Mail Privacy Protection) impacts tracking and engagement. Our iCloud seeds (@icloud.com, @me.com) reveal how Apple's privacy features affect your emails. Critical for understanding iOS/macOS user experience.

ProtonMail & Privacy-Focused Providers

Privacy-focused providers like ProtonMail have unique filtering. Our seeds help identify if encrypted/privacy-conscious users see different placement.

Interpreting Seed Test Results

Inbox Placement Rate

• 95-100%: Excellent - maintain current practices
• 85-95%: Good - minor optimization possible
• 70-85%: Fair - review authentication and content
• 50-70%: Poor - serious deliverability issues
• <50%: Critical - likely blocklisted or auth failing

Spam Placement Rate

• 0-5%: Normal - some spam folder placement is expected
• 5-15%: Warning - check content and authentication
• 15-30%: Problem - review sender reputation
• >30%: Critical - investigate blocklists immediately

Provider-Specific Issues

If one provider shows much worse results than others:

• Gmail low: Check engagement history, may be in promotions legitimately
• Yahoo low: Verify SPF/DKIM alignment, check feedback loops
• Outlook low: Check SmartScreen reputation, scan for blocklists
• All low: Authentication failure or major blocklist issue

Common Seed Testing Use Cases

Pre-Campaign Testing

Test every major campaign before sending to your full list. Catch subject line issues, content problems, or configuration errors before they impact deliverability and sender reputation.

New IP Warmup Validation

When warming up a new sending IP, seed tests confirm you are achieving inbox placement at each stage. Monitor placement improving as you build reputation.

Authentication Verification

After implementing or changing SPF, DKIM, or DMARC, seed testing confirms authentication is working correctly at each provider.

Content Optimization

A/B test subject lines, content layouts, and sending patterns. See which versions achieve better inbox placement across providers.

Deliverability Troubleshooting

When users report emails going to spam, seed tests identify which providers are filtering and help isolate the root cause.

Seed Testing Best Practices

Test Production Content

• Use actual email HTML, not simplified versions
• Include all tracking pixels and links
• Test from production sending infrastructure
• Use real subject lines and preview text

Test Regularly

• Before every major campaign launch
• Weekly during IP warmup periods
• After any authentication changes
• When deliverability metrics decline

Act on Results

• Fix authentication before sending to production
• Adjust content if spam placement is high
• Warm up IPs more gradually if needed
• Monitor and delist from blocklists immediately

Seed Testing Tiers

Free Tier (5 Seed Accounts)

• 2 Gmail accounts (US region)
• 1 Yahoo account
• 1 Outlook account
• 1 Apple Mail account
• 2 tests per day limit
• Basic placement reporting

Pro Tier (20 Seed Accounts) - $49/month

• 8 Gmail accounts (US, EU, CA regions)
• 4 Yahoo/AOL accounts
• 4 Outlook/Hotmail accounts
• 2 Apple Mail accounts
• 1 ProtonMail account
• 1 regional provider account
• Unlimited tests per day
• Screenshot capture of placement
• Historical tracking and trends

Enterprise Tier (50+ Seed Accounts) - Custom Pricing

• 20+ Gmail accounts (all regions)
• 10+ Microsoft accounts (Outlook, Office 365)
• 10+ Yahoo/AOL/Verizon accounts
• 5+ Apple Mail accounts
• Custom regional seeds (Asia, Australia, etc.)
• Business email accounts (Google Workspace, Office 365)
• Industry-specific providers
• White-label reporting
• API access for automation

Limitations of Seed Testing

While seed testing is highly accurate, understand these limitations:

• Sample size: Testing 5-50 accounts cannot predict every recipient's experience
• Engagement: Seed accounts have no engagement history with your emails
• Personal filters: Cannot test user-created rules and filters
• Regional variation: Filtering may vary by country/language
• Time sensitivity: Placement can change throughout the day

Use seed testing alongside other metrics (bounce rate, spam complaints, engagement) for complete deliverability monitoring.