Consent is the legal basis for marketing mail in most jurisdictions and the practical basis for good deliverability: people who asked for mail rarely complain.
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#
- Use an unchecked checkbox or a dedicated signup form; never pre-tick.
- Record timestamp, IP, source, and the exact wording shown at consent.
- Use double opt-in for marketing lists where feasible.
- Separate consent for different purposes (newsletter vs partner offers).
- Refresh consent for contacts older than two years with no engagement.
Frequently asked questions#
Is double opt-in required by law?
Not explicitly in most jurisdictions, but it is the easiest way to prove consent under GDPR and CASL and it improves list quality.