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14/07/2026 4:23 pm
TL;DR: DMARC failures usually trace back to SPF misalignment, broken DKIM signatures, forwarding changes, or new third-party senders added without DNS updates, according to Proofpoint. For identity and security teams, the real issue is governance drift: authentication controls fail when sender inventories, policy enforcement, and vendor onboarding are not kept in lockstep.
NHIMG editorial — based on content published by Proofpoint: How to troubleshoot common DMARC failures
By the numbers:
- Senders of more than 5,000 emails per day who do not pass SPF, DKIM, and DMARC checks may have their messages routed to Junk or rejected outright.
Questions worth separating out
Q: What breaks when DMARC is not aligned with SPF and DKIM?
A: DMARC fails when neither SPF nor DKIM both passes and aligns with the visible From domain.
Q: Why do third-party senders create DMARC governance risk?
A: Third-party senders create risk because every authorised marketing, CRM, or transactional platform must be reflected in DNS and signing policy.
Q: How do security teams know whether DMARC enforcement is actually working?
A: Look for fewer authentication failures from legitimate senders, stable alignment for critical mail flows, and reporting that clearly shows why a message passed or failed.
Practitioner guidance
- Reconcile all authorized senders Build a living inventory of every system that sends on behalf of each domain, including marketing, CRM, support, and transactional platforms.
- Move from monitoring to enforcement deliberately Start with p=none only long enough to capture legitimate traffic, then raise policy to quarantine and reject once all approved senders and forwarding paths are validated.
- Treat forwarding paths as a control dependency Test mailing lists, gateways, and external forwarders because they can break SPF or DKIM even when the source system is configured correctly.
What's in the full article
Proofpoint's full article covers the operational detail this post intentionally leaves for the source:
- Step-by-step SPF, DKIM, and DMARC troubleshooting for specific failure modes in live mail flow.
- Message-header inspection guidance for isolating alignment, signature, and forwarding breakpoints.
- Practical policy tuning from p=none to p=quarantine and p=reject with reporting checkpoints.
- Vendor onboarding checks for marketing, CRM, and transactional senders that need DNS updates.
👉 Read Proofpoint's guide to diagnosing and fixing DMARC failures →
DMARC failures and email authentication gaps: what teams miss?
Explore further
14/07/2026 5:06 pm
DMARC failures are often lifecycle failures, not protocol failures. The article’s root causes, missing authorized senders, broken signatures, forwarding changes, and third-party tools added without DNS updates, all point to ownership drift. In identity terms, the sending domain is behaving like an unmanaged asset with unclear change control. Teams should treat email authentication as a governed lifecycle problem, not a one-time DNS task.
A question worth separating out:
Q: Who is accountable when spoofed email gets through DMARC controls?
A: Accountability usually sits with the teams that own domain policy, mail infrastructure, and vendor onboarding together. DMARC is only effective when DNS changes, message signing, and sender approvals are managed as one process. Security, messaging, and procurement all need a clear role in approving and reviewing senders.
👉 Read our full editorial: DMARC failure modes show where email authentication still breaks
