Choosing wrong either exposes you to neighbors' behavior or leaves an IP too cold to build reputation.
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#
- Estimate steady daily volume; below roughly 50,000 per day, shared pools usually perform better.
- If dedicated, warm up over 4 to 6 weeks and keep volume consistent.
- Separate transactional and marketing onto different IPs or pools.
- Monitor SNDS and Postmaster Tools per IP.
Frequently asked questions#
Do I need a dedicated IP for good deliverability?
No. Domain reputation dominates. Dedicated IPs are for high-volume senders who want isolation.