Overview
A DMARC failure bounce means the receiving server could not confirm your email genuinely came from your domain. DMARC relies on SPF and DKIM alignment. This guide explains how to set them up correctly so your mail passes.
Key Takeaways
- DMARC builds on SPF and DKIM to verify the sending domain.
- Both SPF and DKIM must align with your From domain.
- A published DMARC record tells receivers how to handle failures.
- Correct DNS records fix most DMARC bounces.
Set Up SPF and DKIM
1. Publish an SPF record listing every server allowed to send for your domain.
2. Enable DKIM signing on your mail service and publish its public key in DNS.
3. Confirm the domains used by SPF and DKIM align with your visible From address.
4. Send a test and check that both SPF and DKIM pass.
Publish a DMARC Record
1. Create a DMARC TXT record at _dmarc.yourdomain.
2. Start with a policy of p=none to monitor without blocking.
3. Add a reporting address to receive aggregate reports.
4. Tighten to quarantine or reject once alignment is confirmed.
Tip: Begin with p=none and monitor reports before enforcing quarantine or reject, so you do not accidentally block your own legitimate mail.
Troubleshooting
Problem: Mail still fails DMARC after adding records.
Solution: Confirm SPF and DKIM both align with the From domain, not just a subdomain or relay.
Problem: A third-party sender fails DMARC.
Solution: Add that sender to your SPF and configure DKIM for it, or use a subdomain for that traffic.
Problem: DNS changes seem to have no effect.
Solution: DNS can take time to propagate; wait and re-test, and check for typos in the TXT records.
Problem: You are unsure what is failing.
Solution: Read the DMARC aggregate reports, which show which sources pass or fail alignment.
Conclusion
DMARC bounces come down to SPF and DKIM alignment. Publish correct records, start monitoring with p=none, and tighten the policy once your legitimate mail consistently passes.
About TechHub
This guide is part of the TechHub Knowledge Base. For more step-by-step IT guides and support, visit techhub.com.lk.
