The one-sentence version#
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 you should care#
Delivery rate (accepted by the server) hides the real problem: mail accepted into the spam folder. Placement is the metric that predicts revenue.
The mental model#
Think of inbox placement as a contract between you and the mailbox providers receiving your mail. You publish or configure something they can check; they check it on every message; the result feeds their decision about where your message lands. Everything below is about making that check pass consistently.
Your first setup, step by step#
- 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.
Words you will see#
- Mailbox provider: Gmail, Microsoft, Yahoo, Apple, and the corporate gateways that decide where mail lands.
- Authentication: proof that a message is from who it says it is (SPF, DKIM, DMARC).
- Reputation: the provider's running score of your domain and IP.
- Placement: whether a message reaches the inbox, spam, or is rejected.
Common mistakes#
- Trusting a single seed mailbox per provider; use several with different engagement histories.
- Optimizing for the seed test and not real recipient engagement.
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.