Delivery rate (accepted by the server) hides the real problem: mail accepted into the spam folder. Placement is the metric that predicts revenue.
The metrics that matter#
- Authentication pass rate: share of mail passing SPF, DKIM, and DMARC alignment. Healthy: 99% or higher.
- Spam complaint rate: Gmail enforces at 0.3%; stay under 0.1%.
- Hard bounce rate: under 2%; above 5% triggers platform reviews.
- Inbox placement: above 90% across major providers via seed tests.
- Engagement: click and reply rates by segment; opens are unreliable after Mail Privacy Protection.
Where to read them#
- Google Postmaster Tools for Gmail domain reputation, spam rate, and authentication.
- Microsoft SNDS and JMRP for Outlook.com IP reputation and complaints.
- Your ESP's delivery and bounce reports.
- DMARC aggregate reports for authentication by source.
Improving the numbers#
- 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.