If DMARC passes but SPF fails, what are the concerns and impacts on email deliverability?

Summary

The consensus is that while DMARC can pass if DKIM aligns, thereby ensuring immediate deliverability despite SPF failing, you still shouldn't ignore SPF failures. Experts and official documentation emphasize that SPF failures can point to underlying problems such as unauthorized sending sources, incorrect configurations, or mail forwarding issues. Addressing these failures is key for overall security, preventing potential domain spoofing, maintaining your sender reputation, and averting future delivery problems. It's recommended to investigate SPF records, ensure SPF and DKIM alignment for enhanced security, and monitor failure reports to identify threats.

Key findings

  • DMARC & DKIM Rescue: DMARC can validate email based on DKIM alignment even when SPF fails, maintaining immediate deliverability.
  • SPF Failure Warning: SPF failures can indicate unauthorized sending sources, misconfigurations, or mail forwarding issues.
  • Investigate the 'Why': Understanding the *reason* for SPF failure (alignment vs. unauthorized source) is critical for remediation.
  • Long-term Security: Ignoring SPF failures can expose systems to potential domain spoofing and unauthorized email activity, affecting long-term reputation.
  • Alignment Benefits: Aligning both SPF and DKIM is the best practice for an extra layer of email security and improved deliverability.

Key considerations

  • Audit SPF Records: Ensure SPF records accurately reflect all authorized sending sources to prevent legitimate mail from failing SPF checks.
  • Monitor SPF Reports: Regularly monitor SPF failure reports to identify and address potential security threats or misconfigurations promptly.
  • Align SPF and DKIM: Work towards aligning both SPF and DKIM to provide comprehensive email authentication and improve overall deliverability.
  • Remediate SPF Issues: Actively fix any underlying issues causing SPF failures to enhance email security and protect against spoofing attempts.
  • Prioritize Email Security: Implement a proactive approach to email security, addressing SPF failures not just for immediate delivery but for long-term protection.

What email marketers say
11Marketer opinions

While a passing DMARC, especially due to DKIM alignment, often ensures immediate email deliverability, persistent SPF failures should not be ignored. Experts and marketers agree that SPF failures, even with passing DMARC, can indicate underlying issues like unauthorized sending sources, misconfigurations, or email forwarding problems. Addressing SPF failures is crucial for bolstering email security, preventing potential spoofing, maintaining sender reputation, and mitigating future deliverability problems. Best practices suggest investigating and rectifying SPF configurations for optimal email authentication.

Key opinions

  • Immediate Deliverability: Passing DMARC (due to DKIM) often ensures immediate deliverability despite SPF failures.
  • Underlying Issues: SPF failures can point to unauthorized sending sources, misconfigurations, or email forwarding issues.
  • DKIM Alignment: DKIM alignment is crucial when SPF fails; DMARC relies on either SPF or DKIM for authentication.
  • Security Risks: Unaddressed SPF failures can lead to potential email spoofing and domain exploitation.
  • Best Practice: Rectifying SPF configurations enhances overall email security and reduces vulnerabilities.

Key considerations

  • Investigate SPF Failures: Determine the cause of SPF failures (e.g., unauthorized sources, incorrect records).
  • Monitor Reports: Regularly monitor SPF failure reports to identify and prevent potential issues.
  • Configure SPF Correctly: Ensure SPF records accurately reflect authorized sending sources.
  • Maintain DKIM: Verify DKIM is properly set up and aligned to pass DMARC when SPF fails.
  • Balance Security & Deliverability: Address SPF issues not only for immediate deliverability but also for long-term security and reputation.
Marketer view

Email marketer from EasyDMARC Knowledge Base responds that although DMARC might pass via DKIM, SPF failures can still indicate underlying issues like unauthorized sending sources. They advise investigating and correcting SPF records to prevent potential spoofing.

April 2024 - EasyDMARC Knowledge Base
Marketer view

Email marketer from DNS Records explains that if DMARC passes via DKIM, the SPF failure is less critical for immediate deliverability. However, addressing SPF failures enhances overall email security and prevents potential exploitation of your domain.

March 2022 - DNS Records
Marketer view

Email marketer from Email Geeks responds it should not affect your deliverability and that everything is ok with that set up.

December 2021 - Email Geeks
Marketer view

Email marketer from SparkPost Blog responds that a passing DMARC with a failing SPF means the message is still authenticated, but it's crucial to monitor and address the SPF failure to prevent future deliverability problems and potential spoofing attempts.

June 2023 - SparkPost Blog
Marketer view

Email marketer from Email Deliverability Blog responds that although DMARC passing with DKIM mitigates immediate deliverability issues from SPF failures, it's best practice to rectify SPF configurations. It helps ensure broader email security and reduces vulnerabilities.

October 2024 - Email Deliverability Blog
Marketer view

Email marketer from EmailGeeks Forum shares that even with DMARC passing due to DKIM, ongoing SPF failures can indicate that unauthorized sources are attempting to send emails using your domain. This could lead to future reputation damage.

February 2023 - EmailGeeks Forum
Marketer view

Email marketer from Email Marketing Forum shares that SPF failures, despite DMARC passing via DKIM, can stem from various issues such as email forwarding or incorrect SPF records. Investigating these causes is crucial for maintaining sender reputation.

February 2024 - Email Marketing Forum
Marketer view

Email marketer from StackOverflow answers that although DMARC prioritizes DKIM, its still important to check why the SPF fails. If its because a third party provider is sending the emails, ensure they have DKIM setup and configured to pass DMARC. You can configure DMARC to reject unauthorized emails.

October 2024 - StackOverflow
Marketer view

Email marketer from Postmark Blog shares that while a passing DMARC can provide a degree of protection, relying solely on it without fixing SPF issues is not ideal. They recommend ensuring both SPF and DKIM are correctly configured for optimal deliverability and security.

December 2021 - Postmark Blog
Marketer view

Email marketer from Mailhardener Blog explains that if DMARC passes with DKIM alignment, a failing SPF is not necessarily an immediate concern. They emphasize the importance of DKIM alignment in such scenarios for maintaining deliverability.

October 2023 - Mailhardener Blog
Marketer view

Email marketer from Reddit explains that if DMARC passes due to DKIM, the immediate impact on deliverability might be minimal. However, SPF failures should still be investigated as they could indicate unauthorized use of your domain.

October 2023 - Reddit

What the experts say
5Expert opinions

Experts agree that while DMARC can pass if either SPF or DKIM authenticates an email, with DKIM often serving as the fallback when SPF fails, ignoring SPF failures is unwise. Understanding the *reason* for SPF failure is critical; it might be due to a lack of alignment with the 5322.from address or because the sending IP is unauthorized. Experts recommend fixing SPF issues by publishing DNS records, aligning SPF and DKIM for optimal deliverability, and regularly monitoring SPF failure reports to detect and prevent potential email spoofing and unauthorized email activity.

Key opinions

  • DMARC Flexibility: DMARC authenticates emails if either SPF or DKIM passes; DKIM can compensate for SPF failures.
  • SPF Failure Causes: SPF failures can stem from alignment issues (5322.from) or unauthorized sending IPs.
  • DKIM Importance: Proper DKIM setup is essential, especially when SPF fails, to maintain deliverability.
  • Security Risks: Ignoring SPF failures can expose email systems to spoofing and unauthorized sending.
  • Alignment Matters: Aligning both SPF and DKIM offers an extra layer of security and improved deliverability.

Key considerations

  • Diagnose SPF: Determine *why* SPF is failing (alignment vs. unauthorized source) to guide remediation.
  • Fix SPF Records: Publish or correct SPF DNS records to authorize legitimate sending sources.
  • Monitor Failure Reports: Regularly review SPF failure reports to identify potential security threats.
  • Optimize Alignment: Align SPF and DKIM for improved authentication and deliverability.
  • Prioritize Security: Address SPF failures proactively to prevent spoofing and maintain a secure email environment.
Expert view

Expert from Email Geeks explains that DMARC looks at either SPF or DKIM passing, with both being preferable, but one is enough. They share that many ESPs control the SPF domain but allow for custom DKIM keys, while others allow full alignment of both. They also note that if you see things from IPs that are not yours it could be mail forwarding - SPF will fail, but DKIM should survive and continue to be validated.

September 2021 - Email Geeks
Expert view

Expert from Email Geeks explains the importance of understanding *why* SPF is failing: if it's failing in a DMARC context due to lack of alignment with the 5322.from address, or if it's a hard fail because the IP is not authorized. She states that mail failing SPF needs to be fixed by publishing the DNS record.

October 2024 - Email Geeks
Expert view

Expert from Spam Resource explains that even if DMARC passes due to DKIM alignment, SPF failures should not be ignored. Linford shares that SPF failures could be a sign of unauthorized email activity and recommends regular monitoring of SPF failure reports to identify and prevent potential email spoofing.

April 2023 - Spam Resource
Expert view

Expert from Email Geeks suggests if DMARC is failing because the SPF doesn’t align with the 5322.from, it should be fixed for tidiness rather than delivery impact.

July 2021 - Email Geeks
Expert view

Expert from Word to the Wise answers that While DMARC can pass through DKIM even when SPF fails, it's important to align both SPF and DKIM for optimal deliverability. Betterly emphasizes that a correctly configured SPF record can provide an additional layer of security and help reduce the risk of email spoofing.

August 2024 - Word to the Wise

What the documentation says
4Technical articles

Official documentation uniformly emphasizes that while DMARC can validate emails even when SPF fails—primarily through DKIM alignment—resolving SPF failures remains crucial. Though SPF results are less critical when DMARC passes via DKIM, both Google and Microsoft recommend correctly configuring both SPF and DKIM for comprehensive security. Monitoring SPF failures is advised as they may signal underlying security issues, misconfigurations, or potential vulnerabilities.

Key findings

  • DMARC Reliance: DMARC uses SPF and DKIM to authorize email; DKIM alignment allows DMARC to pass despite SPF failures.
  • Ongoing Vulnerability: SPF failures can indicate underlying security risks or misconfigurations.
  • Google Recommendation: Google recommends configuring both SPF and DKIM for complete email authentication coverage.
  • Microsoft Guidance: Microsoft highlights that DMARC policies apply even when SPF fails and DKIM passes, advising monitoring.
  • Security Concern: The RFC documentation outlines that failing SPF checks is not an optimal setup.

Key considerations

  • Address SPF: Resolve SPF failures even when DMARC passes via DKIM to enhance overall security posture.
  • Monitor SPF: Regularly monitor SPF failure reports to detect and address potential issues promptly.
  • Configure Both: Properly configure both SPF and DKIM to cover different email authentication scenarios.
  • Comprehensive Security: Prioritize a comprehensive security approach encompassing both SPF and DKIM alignment.
  • Implement DMARC: Implementing DMARC helps determine if a message is authorized to use a domain.
Technical article

Documentation from Microsoft explains that messages that fail SPF checks but pass DMARC due to DKIM are still subject to DMARC policies. It is recommended to monitor SPF failures as they may indicate potential security issues or misconfigurations.

October 2021 - Microsoft Documentation
Technical article

Documentation from DMARC.org explains that DMARC uses the results of SPF and DKIM to determine if a message is authorized to use a domain. If DMARC passes due to DKIM, the SPF result is less critical, but resolving SPF failures is still recommended for comprehensive security.

July 2023 - DMARC.org
Technical article

Documentation from Google Workspace Admin Help explains that while DMARC can pass with a DKIM alignment even when SPF fails, Google still recommends configuring both SPF and DKIM correctly. SPF helps in scenarios where DKIM might not be applicable.

July 2022 - Google Workspace Admin Help
Technical article

Documentation from RFC explains the Sender Policy Framework. The RFC defines SPF's mechanisms for verifying sender identity. It also describes that if a system fails SPF, while DMARC passes because of DKIM, messages will still pass DMARC. However it will not be an optimal configuration.

November 2023 - RFC 4408