Bounces, spam traps, and disengaged recipients are the three fastest ways to damage reputation, and all three are prevented by hygiene.
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#
- Verify new signups in real time with an API and use double opt-in for marketing lists.
- Suppress hard bounces immediately and soft bounces after 3 consecutive failures.
- Run a re-engagement campaign at 90 days of inactivity and sunset at 180.
- Remove role accounts (info@, sales@) and disposable domains from marketing lists.
- Audit the list quarterly with a bulk verification service.
Frequently asked questions#
What is a spam trap?
An address that never opted in, maintained by providers and blocklists to catch senders with poor acquisition practices. Hitting one can blocklist your IP or domain.
What bounce rate is acceptable?
Under 2% hard bounces. Above 5% typically triggers ESP account reviews.