How can I use seed lists to test deliverability variations?

Seed list testing directly measures deliverability by observing where emails land across different providers:

How it works: Include seed addresses (test accounts at Gmail, Outlook, Yahoo, etc.) in your sends. Check those accounts to see if mail landed in inbox, spam, or was missing.

Combining with A/B testing: Send both A/B variants with seeds in each group. Compare not just engagement but actual placement rates between variants.

What seed testing reveals:

Inbox placement rate by provider. Which variant has better deliverability. Whether content changes affect filtering decisions.

Limitations: Seed behavior may not perfectly match real recipients. Sample sizes are small. Placement can vary by recipient history.

Tools: Services like GlockApps, Mail Tester, and enterprise platforms provide seed testing infrastructure.

Seed testing makes deliverability visible. Combine it with A/B testing to understand both delivery and engagement.