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
11 marketer 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.
8 Oct 2021 - 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.
4 Aug 2022 - DNS Records
What the experts say
5 expert 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.
6 Feb 2025 - 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.
13 Oct 2023 - Email Geeks
What the documentation says
4 technical 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.
13 Apr 2022 - 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.
23 Jan 2022 - DMARC.org
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