Reputation dominates, but content still tips borderline decisions and drives the complaints that build reputation in the first place.
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#
- Keep a healthy text-to-image ratio and always include a plain-text part.
- Link to your own domain; avoid shorteners and tracking domains with poor reputation.
- Make link text match the destination.
- Test rendering and spam scores before sending.
Frequently asked questions#
Are spam trigger words still a thing?
Much less than a decade ago. Modern filters are statistical and reputation-weighted. Deceptive intent matters more than any single word.