What is a inbox placement?
Also called: inbox placement rate, seed testing
Inbox placement is the share of delivered mail that lands in the inbox rather than spam or a promotions tab. It cannot be measured from your own sending logs, because a provider that files a message as spam still reports it as delivered — it is measured with seed lists or provider feedback.
This is the metric that matters and the one your sending platform cannot show you. Delivery rate counts messages the receiving server accepted. Placement asks where they went afterwards, and the receiving server does not tell you.
Seed testing is the usual approach: send to a set of monitored addresses across the major providers and observe where each copy lands. It is a sample rather than a census, so treat it as directional. Google Postmaster Tools and Microsoft SNDS give provider-side data for their own users, which is narrower but more authoritative.
A collapse in placement with no change in delivery rate almost always points at reputation or authentication rather than content — which is why it is worth ruling out bounces and a blocklist listing before rewriting the copy.
Last reviewed 2026-09-11