Inbox Placement

What is Inbox Placement?

Inbox placement is the percentage of emails that successfully reach the recipient's primary inbox, as opposed to being filtered into spam, promotions, or junk. Unlike delivery rate, which only measures server acceptance, inbox placement reflects where the message actually ends up once it is inside the recipient's mailbox.

Why it matters

A 99 percent delivery rate can still mean 40 percent of your mail is invisible if it is landing in spam. Inbox placement is the metric that actually correlates with opens, clicks, and revenue. Marketers, lifecycle teams, and deliverability engineers should watch it per provider, because Gmail, Outlook, and Yahoo each apply different filters.

How it works

Because mailbox providers do not publish placement data, it is measured indirectly using seed lists: controlled accounts at each provider that receive your campaigns and report back where the message was routed. A seed panel of a few hundred addresses gives statistical confidence about placement across Gmail, Outlook, Apple Mail, and others. The results are usually expressed as three percentages: inbox, spam, and missing.

Examples

• A newsletter achieving 97 percent inbox at Gmail but only 72 percent at Outlook
• A marketer noticing placement drop after a subject line A/B test with spam-trigger words
• A deliverability team tracking placement weekly to catch reputation drift early

Best practices

• Run seed tests before every major campaign, not just after problems
• Monitor placement per mailbox provider; averages hide provider-specific issues
• Correlate placement drops with sending volume, content changes, or list additions
• Fix authentication before tuning content; broken DKIM or DMARC tanks placement first

FAQs

Is inbox placement the same as delivery rate?

No. Delivery rate measures whether the receiving server accepted the message. Inbox placement measures whether that accepted message reached the primary inbox instead of the spam folder.

Why is my Gmail inbox placement lower than Outlook?

Gmail weighs recipient engagement heavily, so low opens drive mail to Promotions or spam. Outlook weighs IP and domain reputation more.

Can Sendkit report my inbox placement?

Sendkit surfaces reputation and engagement signals that strongly correlate with placement, and integrates with seed list providers for explicit measurement.