Summary
Many email senders experience a puzzling situation: their DKIM (DomainKeys Identified Mail) records correctly pass authentication tests, yet Gmail's interface (or other tools like Google Postmaster Tools) reports a DKIM failure. This discrepancy often stems from misunderstandings of DMARC alignment policies, Gmail's specific interpretation of these policies, or even temporary display bugs within Gmail's user interface. The core issue is typically not a true DKIM authentication failure, but rather a misrepresentation of alignment status.
Key findings
- Authentication vs. Alignment: DKIM can technically pass verification (meaning the signature is valid), but still be reported as a failure by Gmail if the DKIM signing domain does not align with the From header domain as per DMARC requirements. For more on this, consult our guide on DMARC, SPF, and DKIM basics.
- DMARC Alignment Modes: DMARC policies use strict (s) or relaxed (r) alignment for both SPF and DKIM. Relaxed alignment allows subdomains to align with the organizational domain. Gmail's display might sometimes strictly enforce alignment even if your DMARC record specifies relaxed alignment (adkim=r).Gmail Interface Bug: There are instances where Gmail's internal summary table, visible to users, inaccurately reports DKIM failures even when the technical email headers show a DKIM pass and DMARC alignment. This appears to be a bug in their display mechanism, not an actual deliverability issue. Some users reported it curing itself over time.Impact on Deliverability: In many reported cases, despite the 'DKIM FAIL' message in the UI, emails are still successfully delivered to the inbox, indicating the underlying authentication passed. The issue is primarily one of misleading user feedback rather than actual mail rejection. This is similar to why Gmail shows 'via' even when DMARC passes.
- Troubleshooting Difficulty: Redacted or incomplete email headers make it nearly impossible for experts to diagnose the precise cause of such discrepancies. Full, unredacted headers are essential for accurate analysis.
Key considerations
- Verify Full Headers: Always examine the full email headers (e.g., in Gmail by clicking 'Show original') to see the actual Authentication-Results line. This provides the most accurate status of DKIM, SPF, and DMARC. This is crucial when DKIM fails for one ISP but passes for another.
- Understand DMARC Alignment: Ensure your DMARC record's adkim tag correctly reflects your intended alignment (strict or relaxed). If you are using relaxed alignment, and Gmail is misreporting, there may be little to do but wait for a Google fix or switch to strict alignment if your setup allows. More details on Gmail's security requirements are available.
- Monitor Deliverability Beyond UI: If emails are reaching the inbox and you're not seeing bounces, the UI display issue might be cosmetic. However, continued monitoring of your Google Postmaster Tools and DMARC aggregate reports (RUAs) is recommended to catch any actual authentication failures that might impact deliverability.
What email marketers say
Email marketers often find themselves confused and concerned when Gmail (or other mailboxes) reports a DKIM failure, despite their own checks indicating a pass. This disparity often leads to troubleshooting efforts that are unnecessary or misdirected, as the real issue might lie in how Gmail's user interface presents authentication results versus the actual technical validation. The primary concern for marketers is typically if this perceived failure impacts their email deliverability or sender reputation.
Key opinions
- Confusion Reigns: Many marketers are bewildered when they see a 'DKIM FAIL' message, especially if their DMARC reports or other tools show DKIM is passing. This causes unnecessary concern and troubleshooting.
- Impact on Perception: The visible 'fail' message, even if not affecting delivery, can create a perception of issues for recipients or internal stakeholders, leading to questions about email security and professionalism.
- Intermittent Nature: Some marketers observe that the issue appears and disappears without clear action on their part, suggesting an external factor like a bug or gradual rollout of changes by Gmail. This aligns with findings when DKIM fails at some ISPs but not others.
- Focus on Delivery: When emails are still reaching the inbox, marketers often conclude that the displayed 'fail' is a cosmetic issue. However, they remain vigilant, consulting email deliverability tests to ensure underlying issues are not present.
Key considerations
- Educate Stakeholders: Marketers should be prepared to explain to clients or internal teams that a 'DKIM FAIL' displayed in Gmail's summary can be a visual bug and not necessarily an indicator of poor sender reputation or deliverability issues. Understanding the full header is key.
- Rely on DMARC Reports: Instead of Gmail's UI, marketers should regularly check their DMARC aggregate reports (RUAs) for a true picture of authentication success rates across all receiving mailboxes. This is where actual failures or anomalies would be consistently reported. Review your DMARC data carefully.
- Test Thoroughly: Send test emails to various Gmail addresses and other email providers to see consistent authentication results. This helps confirm whether the issue is isolated to a specific Gmail account or a broader problem. For related issues, see why DKIM and DMARC might be failing in Gmail.
Marketer view
An Email Geeks marketer observed their email configuration showing 'DKIM: 'FAIL' with domain ibm.domain.com' due to unaligned From and DKIM domains in the Gmail 'Original Message' area. This occurred despite their headers indicating that DKIM, SPF, and DMARC were passing, creating significant confusion about the actual authentication status.
Marketer view
A Marketer from Spiceworks Community indicated that they frequently encounter situations where SPF and DKIM appear to fail in DMARC aggregate reports, particularly for Microsoft 365 users. They noted that the underlying configuration might seem correct, but the reports suggest otherwise, necessitating deeper investigation into alignment and reporting mechanisms.
What the experts say
Experts in email deliverability often shed light on the nuances behind DKIM reporting discrepancies, particularly with Gmail. They point out that what appears as a 'failure' in a user-facing summary might not be a true authentication failure but rather a misinterpretation of DMARC alignment rules or a glitch in the receiving mailbox provider's display logic. Their insights emphasize the importance of distinguishing between actual technical passes and how these are presented to end-users.
Key opinions
- Alignment Discrepancy: Experts agree that Gmail's reporting of DKIM failures often occurs when the DKIM domain doesn't align with the RFC5322.From domain, even if the DKIM signature itself is technically valid and passing. This is typically what Gmail means by 'unaligned From and DKIM domains'.
- Gmail's Reporting Bug: Several experts suggest that Gmail's little summary table in the email header display (seen by users) has a bug related to checking alignment. It sometimes incorrectly flags things as unaligned when they are, in fact, aligned according to DMARC's relaxed alignment rules. This bug is particularly frustrating for senders.
- Relaxed vs. Strict Alignment: The issue might stem from Gmail evaluating a strict alignment when the sender's DMARC record (via the adkim=r) should dictate relaxed alignment. If the DMARC record specifies strict alignment (adkim=s), then a non-exact match would correctly result in a failure.
- Underlying Pass: Despite the 'FAIL' in the UI, Google often correctly identifies the mail as aligned and passing during the SMTP session, as evidenced in the full Authentication-Results header. This reinforces the idea that the problem is a display error. For more, see decoding DKIM temperror.
Key considerations
- Diagnose with Full Headers: Experts strongly advise obtaining full, unredacted email headers for accurate diagnosis. Without this, it is difficult to determine if the issue is a genuine configuration error or a reporting anomaly. This is especially true when DKIM fails in Hotmail but passes in Gmail.
- Distinguish UI from Reality: It is critical for senders to understand that Gmail's simplified summary can be misleading. The actual deliverability and authentication status are better reflected in the detailed technical headers. This distinction is vital for improving email deliverability.
- Monitor for Gradual Fixes: If the issue is a Gmail bug, it may resolve itself over time or be rolled out gradually to various recipient accounts. Continuous monitoring and patience might be necessary. This situation is similar to Google's real-time DKIM system causing errors.
Expert view
An Expert from Email Geeks states that the problem often arises because a sender's domains are unaligned. They emphasize that without seeing the full, unredacted data, it is impossible to precisely determine why the domains are unaligned in the SPF and DKIM records, which prevents providing specific fixes.
Expert view
An Expert from Word to the Wise explains that Gmail appears to be reporting DKIM failures even when DKIM technically passes, particularly when the DKIM domain does not align with the RFC5322.From domain. They suggest that Gmail's reporting has changed to reflect this strict alignment interpretation.
What the documentation says
Official documentation from email authentication standards and major email providers clarifies how DKIM should function and what constitutes proper alignment. While these documents define the technical specifications, their interpretation and implementation by various mail services can lead to discrepancies, particularly in user-facing reports. Understanding the foundational definitions is crucial for diagnosing perceived authentication failures.
Key findings
- DKIM Authentication: DKIM verifies that an email's content has not been tampered with in transit and that it originates from a domain authorized by the sender. This involves cryptographic signing and public key lookups in DNS.
- DMARC Alignment Principle: For DMARC to pass, either SPF or DKIM must pass and align with the RFC5322.From (header From) domain. Alignment means the authenticated domain (from SPF's MailFrom or DKIM's d= tag) matches the organizational domain of the header From. Refer to the DKIM signature guide.
- Relaxed Alignment: Under relaxed alignment (specified by adkim=r in DMARC), a DKIM signing domain that is a subdomain of the RFC5322.From domain (e.g., sub.example.com and example.com) is considered aligned.
- Google's Stated Alignment: Google's documentation indicates that DKIM aligns when it passes for both the domain and its subdomain. This implies support for relaxed alignment in their core authentication logic.
Key considerations
- Adherence to RFCs: Email systems are expected to follow RFC standards for DKIM and DMARC. Any deviation in reporting, especially in user interfaces, can cause confusion for senders who have configured their domains according to these standards. For more, explore what RFC 5322 says versus what works.
- Source of Truth: The authoritative source for authentication results is the Authentication-Results header field, rather than simplified UI displays which may aggregate or misinterpret detailed results. Review RFC 7601 Section 2.7 for more.
Technical article
The RFC 6376, which defines DKIM, specifies the mechanisms for email signing and verification. It establishes how a DKIM signature should be generated and how a receiving mail server should use the DNS to retrieve the public key to validate the signature, ensuring message integrity and sender authentication.
Technical article
Google's documentation on AMP for Email security requirements states that DKIM aligns when it passes for both the domain and its subdomain. This implies that Google's systems are designed to support relaxed alignment, which makes discrepancies in the user interface particularly confusing for senders.
Related resources
6 resources
Related pages
Why is Microsoft DKIM failing when Gmail passes, and how to fix it?
Why is DKIM failing at some ISPs but not others, and how can I fix it?
Why are my DKIM and DMARC failing in Gmail, and how can I fix it?
A simple guide to DMARC, SPF, and DKIM
List of DMARC tags and their meanings
Ultimate Guide to Google Postmaster Tools V2
Why Your Emails Are Going to Spam in 2024 and How to Fix It
Decoding DKIM temperror: what it is and how to fix it
Why is Gmail showing a warning message despite passing DMARC?
Understanding and troubleshooting DMARC reports from Google and Yahoo
