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DMARC failures can leave your organization vulnerable to phishing and spoofing attacks. Understanding why these failures happen is the first step toward a robust email security posture.
The most common cause is misaligned DKIM signatures. When a service like G Suite signs mail with its own domain (e.g., d=example.gappssmtp.com) instead of your domain, DMARC sees the signature as unauthenticated and flags the message.
SPF checks the envelope sender IP against authorized hosts. If the SPF record does not include the sending service, DMARC treats the message as unauthenticated, even if DKIM passes. Ensure all legitimate outbound IPs are listed in your SPF record.
Platforms like SendGrid or MailChimp send mail on your behalf but use their own DKIM domains. Without adding the provider’s SPF include and DKIM public key to your DNS, the messages fail alignment and DMARC reports them as failures.
Yes. Forwarding services often modify the message header, breaking the DKIM signature. If the forwarder does not preserve SPF alignment, DMARC will also fail. Use ARC (Authenticated Received Chain) or avoid forwarding when possible.
Start by enabling DMARC monitoring (p=none) to collect data without affecting delivery. Review the aggregate reports to identify which sources are failing, then add or correct SPF/DKIM records for those sources. Once alignment is achieved, gradually move to a stricter policy (p=quarantine, then p=reject).
Use Palisade’s DKIM signing tool to test your selector and public key. The tool will confirm that the DNS record is reachable and that the signature matches the expected value.
BIMI builds on DMARC to display your brand logo in supporting inboxes. It requires a DMARC policy of at least quarantine. Verify your BIMI setup with Palisade’s BIMI verification tool.
Run Palisade’s SPF record checker. It will highlight missing mechanisms, too many DNS lookups, or syntax mistakes that could cause DMARC failures.
Yes. Palisade provides an email security score dashboard that aggregates DMARC, SPF, DKIM, and BIMI data in one place, making troubleshooting faster.
After you have identified and whitelisted all legitimate sources, and your aggregate reports show < 5% failure rate, you can shift to p=quarantine. Monitor the impact for a week, then consider p=reject for maximum protection.
By following these steps and using Palisade’s suite of email authentication tools, you can turn DMARC failures into a proactive security advantage.
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