What inbox placement is#
Inbox placement is the percentage of sent mail that lands in the primary inbox rather than spam, promotions, or being blocked. It is measured with seed lists across major providers and panel data from real mailboxes.
Why it matters#
Delivery rate (accepted by the server) hides the real problem: mail accepted into the spam folder. Placement is the metric that predicts revenue.
How mailbox providers use it#
Gmail, Microsoft, and Yahoo combine authentication results, sender reputation, and recipient engagement into a placement decision made per message. Inbox placement feeds directly into that model, and weaknesses compound with other signals.
How to measure the impact#
- Baseline inbox placement with seed tests before any change.
- Make one change at a time and hold volume steady.
- Re-test after 48 to 72 hours; provider models need time to update.
- Track Postmaster Tools and SNDS alongside your seed results.
Improving it#
- Create seed accounts at Gmail, Outlook, Yahoo, iCloud, and key B2B gateways.
- Send each campaign to the seed list before the full send.
- Record inbox, spam, promotions, and missing counts per provider.
- Correlate drops with content, sending domain, or list segment changes.
- Fix authentication, reputation, or content issues before scaling.
Frequently asked questions#
Why does mail land in Gmail Promotions?
Gmail classifies by content and sender behavior. Promotions is not spam and often performs well; do not over-optimize to escape it.
What is a good inbox placement rate?
Above 90% is healthy. Below 80% indicates a reputation or authentication problem.