Forwarding and mailing lists are the largest source of legitimate DMARC failures. ARC lets receivers accept mail that would otherwise be quarantined under p=reject.
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#
- Check whether your inbound gateway or mailing-list software supports ARC sealing.
- Enable ARC sealing on any system that modifies and re-sends mail.
- Verify ARC-Seal, ARC-Message-Signature, and ARC-Authentication-Results headers appear on forwarded mail.
- Confirm downstream receivers (Gmail, Microsoft) honor your seals by checking Authentication-Results for arc=pass.
Frequently asked questions#
Do I need ARC as a sender?
No. ARC is implemented by intermediaries and receivers. Senders benefit indirectly when their mail is forwarded.
Which providers honor ARC?
Gmail, Microsoft, and Yahoo all evaluate ARC when deciding whether to override a DMARC failure.