--- title: "Why DMARC Fails: Complete Troubleshooting Guide (2026) | DMARC Report" description: "DMARC fails when both SPF and DKIM fail to align with the From header. The 5 most common causes: unauthorized third-party senders, SPF alignment mismatch, missing DKIM signatures, email forwarding, and misconfigured DNS records. Here" image: "https://dmarcreport.com/og/blog/why-dmarc-fails-troubleshooting-guide-2026.png" canonical: "https://dmarcreport.com/blog/why-dmarc-fails-troubleshooting-guide-2026/" --- Quick Answer DMARC fails when both SPF alignment and DKIM alignment fail against the From header. The 5 most common causes are: (1) unauthorized third-party senders not in your SPF record, (2) SPF alignment mismatch (Return-Path domain differs from From domain), Related: [Free DMARC Checker](/tools/dmarc-checker/) Share [ ](https://www.linkedin.com/sharing/share-offsite/?url=undefined%2Fblog%2Fwhy-dmarc-fails-troubleshooting-guide-2026%2F "Share on LinkedIn") [ ](https://twitter.com/intent/tweet?text=Why%20DMARC%20Fails%3A%20Complete%20Troubleshooting%20Guide%20%282026%29&url=undefined%2Fblog%2Fwhy-dmarc-fails-troubleshooting-guide-2026%2F "Share on X/Twitter") [ ](https://www.facebook.com/sharer/sharer.php?u=undefined%2Fblog%2Fwhy-dmarc-fails-troubleshooting-guide-2026%2F "Share on Facebook") [ ](https://reddit.com/submit?url=undefined%2Fblog%2Fwhy-dmarc-fails-troubleshooting-guide-2026%2F&title=Why%20DMARC%20Fails%3A%20Complete%20Troubleshooting%20Guide%20%282026%29 "Share on Reddit") [ ](mailto:?subject=Why%20DMARC%20Fails%3A%20Complete%20Troubleshooting%20Guide%20%282026%29&body=Check out this article: undefined%2Fblog%2Fwhy-dmarc-fails-troubleshooting-guide-2026%2F "Share via Email") ![Why DMARC Fails: Complete Troubleshooting Guide (2026)](https://media.mailhop.org/dmarcreport/images/2022/04/dmarc-report-4236.jpg) ## Try Our Free DMARC Checker Validate your DMARC policy, check alignment settings, and verify reporting configuration. [ Check DMARC Record → ](/tools/dmarc-checker/) \*\*DMARC fails when an email from your domain fails BOTH SPF alignment and DKIM alignment with the `From` header. If either one passes and aligns, DMARC passes - the failure means neither authentication method could verify the sender as authorized. This is either a legitimate sender that’s misconfigured, or an actual spoofing attempt. Per [RFC 7489](https://datatracker.ietf.org/doc/html/rfc7489), DMARC evaluates alignment, not just authentication. SPF can PASS while DMARC still FAILS because the SPF-verified domain doesn’t match the From header. This is the most common source of confusion. > Email authentication isn’t just about preventing spoofing - it’s about trust, says Vasile Diaconu, Operations Lead at DuoCircle. Every email your organization sends either builds trust or erodes it. SPF, DKIM, and DMARC are the foundation of that trust. Without them, receivers have no way to distinguish your legitimate email from an attacker’s. ## The 5 Most Common Causes of DMARC Failure ## 1\. Unauthorized Third-Party Senders **Symptoms:** DMARC reports show failures from IPs you don’t recognize, or from services you use but haven’t authorized. **Cause:** You added a new CRM (Salesforce, HubSpot), newsletter tool (Mailchimp, SendGrid), or support desk (Zendesk, Freshdesk) that sends email from your domain, but didn’t add its `include:` to your SPF record or enable DKIM signing. **Fix:** Identify the sending service from the IP in your DMARC report, then: - Add their `include:` mechanism to your SPF record - Enable DKIM signing in their admin console - Verify with [DMARC Report](/) that the source now passes ## 2\. SPF Alignment Mismatch **Symptoms:** SPF shows `pass` in your report, but DMARC disposition is `fail`. **Cause:** The domain in the `Return-Path` (envelope sender) passed SPF, but it doesn’t match the domain in the visible `From` header. Example: your CRM sends with Return-Path `bounce@crm-vendor.com` but From `you@yourdomain.com` \- SPF passes for crm-vendor.com, not for yourdomain.com. **Fix:** Configure a custom Return-Path subdomain in your sending service (e.g., `mail.yourdomain.com`) so SPF aligns with your From domain. ## 3\. Missing or Expired DKIM Signatures **Symptoms:** DKIM shows `fail` or `none` in reports. SPF alignment also fails. **Cause:** The sending service isn’t signing messages with DKIM, or the DKIM key has expired/been rotated without updating DNS. **Fix:** \- Check your DKIM selectors with the [DKIM Inspector](/tools/dkim-lookup/) - Enable DKIM in the sending service’s admin console - Publish the new public key TXT record if prompted ## 4\. Email Forwarding **Symptoms:** Legitimate recipients report your email going to spam. DMARC reports show failures from forwarding server IPs. **Cause:** When email is forwarded, the forwarding server’s IP is not in your SPF record. SPF fails. If DKIM isn’t configured or the forwarder modifies the message (adding a footer, etc.), DKIM also fails. Both fail = DMARC fails. **Fix:** DKIM is the primary defense against forwarding failures (signatures survive forwarding if the content isn’t modified). Ensure DKIM is enabled for all your sending services. For mailing lists, ARC ([RFC 8617](https://datatracker.ietf.org/doc/html/rfc8617)) preserves authentication across forwarding chains. ## 5\. DNS Misconfigurations **Symptoms:** Intermittent DMARC failures, or DMARC passes for some receivers but fails for others. **Cause:** Typos in SPF/DKIM/DMARC records, multiple SPF records on the same domain (PermError), expired DKIM keys, or DNS propagation delays after changes. **Fix:** Run a [full domain authentication check](/tools/domain-auth-checker/) to verify all records are published correctly. ## How to Diagnose DMARC Failures 1. \*\*Check your DMARC reports in [DMARC Report](/) \- identify which source IPs are failing 2. **Reverse-DNS the failing IP** \- identify the sender (DMARC Report does this automatically via source classification) 3. **Check SPF for that sender** \- is their IP or include in your SPF record? 4. **Check DKIM for that sender** \- is DKIM signing enabled? 5. \*\*Fix the root cause and verify the next day’s reports show the source passing [Check your DMARC record →](/tools/dmarc-checker/) [Start monitoring failures →](https://app.dmarcreport.com/) ## Topics [ DMARC ](/tags/dmarc/)[ email security ](/tags/email-security/) ![Brad Slavin](https://media.mailhop.org/dmarcreport/images/team/brad-slavin.jpg) [ Brad Slavin ](/authors/brad-slavin/) General Manager Founder and General Manager of DuoCircle. Product strategy and commercial lead for DMARC Report's 2,000+ customer base. [LinkedIn Profile →](https://www.linkedin.com/in/bradslavin) ## Take control of your DMARC reports Turn raw XML into actionable dashboards. Start free - no credit card required. [Start Free Trial](https://app.dmarcreport.com/) [Check Your DMARC Record](/tools/dmarc-checker/) ## Related Articles [ Foundational 8m 10 Critical Learnings From Verizon’s 2021 DBIR - A DMARCReport Perspective Nov 25, 2025 ](/blog/10-critical-learnings-from-verizons-2021-dbir-a-dmarcreport-perspective/)[ Foundational 12m 10 DNS Blacklist Insights That Improve Email Security And Deliverability Fast Nov 14, 2025 ](/blog/10-dns-blacklist-insights-to-improve-email-security-and-deliverability/)[ Foundational 12m 10 Email Spoofing Detection Tools That Dramatically Improve Brand Protection Nov 11, 2025 ](/blog/10-email-spoofing-detection-tools-that-dramatically-improve-brand-protection/)[ Foundational 12m 10 Reasons SPF Filtering Is Critical For Email Security Nov 19, 2025 ](/blog/10-reasons-spf-filtering-is-critical-for-email-security/) ```json {"@context":"https://schema.org","@type":"Organization","@id":"https://www.wikidata.org/wiki/Q138898167","name":"DMARC Report","url":"https://dmarcreport.com","logo":{"@type":"ImageObject","url":"https://dmarcreport.com/images/dmarcreport-logo.png"},"description":"DMARC reporting and email authentication management. 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