What Is Seed List?
A seed list is a set of test email addresses across major providers — Gmail, Outlook, Yahoo, and others — used to measure inbox placement. You send a campaign to the seeds and record where each copy lands (inbox, spam, or promotions) to gauge deliverability before or during a real send.
Seed lists power inbox placement testing. Because the addresses are controlled, you can inspect exactly which folder each message reached on each provider, producing a per-ESP placement breakdown you cannot get from open rates alone.
Good seed lists are diverse and representative: they cover the providers your real audience uses, in roughly the right proportions, so the results predict real-world placement. A Gmail-heavy audience needs a Gmail-heavy seed list.
Seed testing has limits — it measures placement for the seed accounts, not personalized filtering for individual real recipients — but it remains the most direct way to see inbox versus spam placement across providers.
MailPilot runs placement tests across a representative set of provider mailboxes and reports inbox vs spam vs promotions per ESP, so you see real placement, not a blended guess.
See placement testing →