Summary
It can be perplexing when Google Postmaster Tools (GPT) reports DKIM and DMARC authentication failures, yet other tools, like Hubspot, indicate that your DNS records are correctly configured. This common discrepancy often arises because GPT analyzes the actual email traffic it receives, not just your published DNS records. While your records might be perfectly set up, issues can occur during the email sending process, leading to authentication failures in the eyes of major receivers like Google. Understanding this distinction is key to diagnosing and resolving the problem, often requiring a deep dive into your DMARC aggregate reports (RUAs) to pinpoint the exact cause.
Key findings
- GPT vs. DNS Checkers: Google Postmaster Tools evaluates email authentication based on the emails it actually receives, not solely on whether DNS records exist. Other tools primarily check for the presence and syntax of your DNS records.
- Real-world Authentication: Even with correct DNS records, issues like email forwarding, modifications to email content during transit, or incorrect configurations on the sending platform can lead to authentication failures (such as DKIM signature breaks).
- DMARC Reports are Critical: DMARC reports (RUA records) provide detailed insights into where and why your emails are failing authentication. These reports are generally not human-readable and require a DMARC monitoring service for proper analysis. For more on this, consider our guide on understanding and troubleshooting DMARC reports.
- Spoofing or Unknown Mailstreams: Authentication failures in GPT might indicate that your domain is being spoofed by unauthorized senders, or that there are legitimate email streams using your domain that you are not aware of.
- Specific Platform Behavior: Some email service providers (ESPs) may have specific ways of handling SPF and DKIM that can impact how GPT reports authentication. For instance, an ESP might not use custom SPF records directly from your domain, affecting how SPF alignment is perceived by GPT.
Key considerations
- Review DMARC Aggregate Reports: These reports offer the most comprehensive view of your email authentication status, including sources of failure. They are essential for debugging DMARC alignment and authentication issues.
- Check Sending Configurations: Verify that your sending platform is correctly signing emails with DKIM and that SPF is aligned. Small misconfigurations can lead to authentication failures at the receiving end, even if DNS records are fine. Kinsta provides guidance on how to fix DMARC fail errors.
- Investigate Unknown IP Addresses: Utilize GPT's IP reputation section to see if unfamiliar IP addresses are sending mail using your domain. If so, this could indicate spoofing or an unmanaged sending service. You can learn more about this in our ultimate guide to Google Postmaster Tools V2.
- Address DMARC RUA Access: Ensure the email address designated to receive DMARC reports is accessible and properly configured to handle XML data (preferably through a DMARC aggregator). Incorrect settings (e.g., internal-only Google Groups) will prevent you from accessing crucial data.
- Consider Google Support: If all other troubleshooting steps fail and you're certain about your setup, contacting Google support may be necessary to understand the nuances of their reporting for your domain.
What email marketers say
Email marketers often face a bewildering situation when their Google Postmaster Tools (GPT) dashboard shows authentication failures for DKIM and DMARC, even when DNS checkers report no errors. This discrepancy highlights a common challenge: the difference between a static DNS record check and the dynamic, real-time evaluation of email authentication by mail receivers like Google. Marketers frequently find themselves questioning the source of truth, emphasizing the need for robust DMARC reporting to gain clarity and debug these complex issues. The community often discusses the need to look beyond mere DNS setup and delve into the actual email delivery process and potential external factors.
Key opinions
- Conflicting Information is Common: Many marketers express confusion when GPT reports failures while other reputable tools confirm correct DNS setup. This implies a disconnect between theoretical DNS configuration and practical email authentication outcomes.
- DMARC Reports are the Definitive Source: There's a strong consensus that DMARC aggregate reports are essential. They provide the most granular data on authentication failures, including the source IPs, which is information that GPT may not fully reveal or make easily accessible.
- Potential for Spoofing: Marketers recognize that authentication failures could be due to malicious actors spoofing their domain, even if their legitimate sending is pristine. The DMARC reports help confirm or rule out this possibility.
- Hubspot Specifics: When sending via Hubspot, marketers note that Hubspot's SPF implementation doesn't use custom SPF directly. This means SPF success rates in GPT might only reflect 1:1 mail, not bulk sends, which can complicate understanding. Our article on DKIM and DMARC failures in ConvertKit provides context for ESP-specific issues.
Key considerations
- Don't Just Trust DNS Checkers: While DNS checkers confirm record existence, they don't validate how actual email flows interact with those records. Focus on how Google (and other ISPs) are receiving your mail.
- Set Up DMARC Monitoring: If not already in place, marketers should prioritize setting up DMARC monitoring to convert raw XML reports into actionable data. Without this, diagnosing the root cause of failures becomes nearly impossible. Review our guide on debugging DMARC authentication and alignment issues.
- Verify All Sending IPs: Even if you believe you only send from specific IPs, check GPT's IP reputation section. Unexpected IPs could reveal unmanaged mail streams or spoofing attempts. Medium provides insights on testing DNS records for errors.
- Understand GPT's Scope: Recognize that GPT shows authentication for all mail using a given domain, whether authorized or unauthorized. This broader scope can lead to reported failures even when your controlled sending is compliant.
Marketer view
Email marketer from Email Geeks notes a discrepancy between Google Postmaster Tools and other DNS checkers, indicating uncertainty about which source to trust regarding DKIM and DMARC authentication failures despite correct DNS records. They are not sure who to believe.
Marketer view
Email marketer from Email Geeks states that while Google Postmaster Tools should display comprehensive data, their primary sending is limited to a single email address for mass campaigns. They are investigating DMARC reports to confirm the scope of the reported issues.
What the experts say
Email deliverability experts agree that discrepancies between DNS checkers and Google Postmaster Tools are a complex issue, primarily because GPT provides a view of email authentication from the recipient's perspective. Experts consistently highlight that merely having correct DNS records for SPF, DKIM, and DMARC does not guarantee successful authentication. The actual email flow, including potential spoofing, unintended mail streams, or subtle misconfigurations in the sending infrastructure, plays a much more significant role. The consensus is strong: DMARC aggregate reports are the indispensable tool for diagnosing these real-world authentication failures, as GPT's data can be generalized and less granular for specific troubleshooting.
Key opinions
- Google's Perspective: Experts emphasize that Google Postmaster Tools reports on the authentication status of emails as Google *receives* them, not just on the integrity of your DNS records. This means that a perfectly configured DNS record can still result in a failure if the email itself is altered or improperly sent.
- DKIM Signature Failures: If DKIM is failing in GPT, it strongly suggests an issue with the email's signature (e.g., body hash mismatch), which can occur if the email content or headers are modified in transit after the signature is applied.
- Beyond Authorized Sending: GPT's reports can encompass both authorized and unauthorized (spoofed) use of your domain. Therefore, failures might not be from your legitimate campaigns but from other actors. This is a common reason why Google Postmaster Tools shows authentication failures despite SPF being set up, a topic explored in our troubleshooting guide.
- The Need for DMARC Reports: Raw DMARC reports are unreadable, so using a DMARC aggregator service is critical for transforming them into actionable intelligence. These reports provide the necessary detail to identify the specific sending IPs and authentication outcomes for all mail streams.
- GPT Data Nuances: Experts acknowledge that Google Postmaster Tools can be a 'strange and mysterious beast' regarding the exact data it includes and excludes, making direct troubleshooting based solely on GPT challenging without DMARC reports.
Key considerations
- Prioritize DMARC Report Access: Ensure your DMARC record's RUA tag points to a functional mailbox or, ideally, a DMARC monitoring service. Without this, you're flying blind, as the raw reports are the single best diagnostic tool.
- Comprehensive IP Review: Actively check the IP address screen in GPT (if available for your domain) to identify all IPs sending mail on your behalf. Any unknown IPs should be investigated immediately as potential sources of failure or spoofing.
- Understand Alignment: DMARC requires either SPF or DKIM to align with the 'From' domain. Misalignment is a frequent cause of DMARC failures, even when SPF/DKIM pass independently. Our page on DMARC authentication failures details this.
- Segment Mailstreams: If you use multiple sending platforms (e.g., CRM, transactional email service), ensure each is properly configured for authentication and that all are accounted for in your SPF and DKIM records. This helps prevent unknown mail streams from causing failures.
- Consult Official Documentation: For specific details on how Google handles authentication and reporting, always refer to their official documentation. This helps to clarify how their systems interpret and report on your email traffic. More resources on Google Postmaster Tools compliance issues are available.
Expert view
Email deliverability expert from Email Geeks highlights that Google evaluates email authentication based on the email it actually receives, not merely on the DNS records. This means that a domain's DNS records can be perfectly fine, yet its authentication status can still be broken due to other factors.
Expert view
Email deliverability expert from Email Geeks advises that if DKIM is failing, it strongly indicates a signature failure. Such failures can occur if the email content or headers are altered after the DKIM signature is applied, leading to invalidation by the receiving server.
What the documentation says
Official documentation for email authentication protocols like DMARC, DKIM, and SPF outlines how these mechanisms are designed to verify sender identity and ensure message integrity. While DNS records are the foundation for publishing these policies, the actual authentication process happens at the receiving mail server, which evaluates each incoming email against the published records and defined policies. Documentation highlights that issues beyond simple DNS configuration, such as message alteration in transit, improper signing by sending infrastructure, or misalignment of domains, can lead to authentication failures. Tools like Google Postmaster Tools aggregate these real-world results, providing a macroscopic view that may differ from a simple DNS lookup, underscoring the need for comprehensive DMARC reporting to pinpoint exact causes.
Key findings
- Protocol Operation: DKIM applies a digital signature to email headers and body, which is then verified against a public key in DNS. SPF authorizes sending IP addresses via a DNS record. DMARC builds upon these, requiring at least one to pass and align with the From: domain.
- Real-time Validation: Authentication validation is performed by the receiving Mail Transfer Agent (MTA) for each individual message, not by pre-checking DNS records. This live evaluation accounts for potential transit-time issues.
- Message Modification: Any alteration to the signed parts of an email (headers or body) after DKIM signing, such as by mailing lists or forwarding services, will cause a DKIM signature to fail validation.
- DMARC Alignment: For DMARC to pass, either the SPF-authenticated domain or the DKIM-signed domain must align (be the same or a subdomain of) the domain in the RFC5322.From header. Failure to align leads to DMARC failure regardless of individual SPF/DKIM pass statuses.
Key considerations
- Sender Implementation: Email senders must ensure their mail servers or ESPs correctly implement SPF (including all authorized sending IPs) and properly sign emails with DKIM. Mismatches or omissions here will result in authentication failures.
- DMARC Policy Impact: The DMARC policy (p=none, p=quarantine, p=reject) dictates how receiving servers should handle emails that fail DMARC authentication. A p=none policy allows monitoring without impacting delivery.
- DMARC Reporting Importance: The 'rua' (aggregate report URI) tag in a DMARC record is essential for receiving XML reports that detail authentication outcomes for all mail claiming to be from your domain. These reports are the primary mechanism for identifying and troubleshooting issues.
- DNS Propagation: Changes to DNS records (SPF, DKIM, DMARC) require time to propagate across the internet. Instantaneous checks might not reflect the global state, leading to temporary discrepancies.
Technical article
Documentation from DMARC.org explains that DMARC enables domain owners to protect their domain from unauthorized use by defining policies on how receiving mail servers should handle unauthenticated emails and providing reporting mechanisms. This framework relies on both SPF and DKIM for authentication.
Technical article
Documentation from RFC 6376, which defines DKIM, indicates that DKIM provides a method for an email sending domain to cryptographically sign outgoing messages. This signature allows the receiving server to verify the message's authenticity and integrity by comparing it against a public key published in the domain's DNS.
Related resources
2 resources
Related pages
Why is Google Postmaster Tools (GPT) showing incorrect SPF and DKIM authentication rates?
Understanding and troubleshooting DMARC reports from Google and Yahoo
Ultimate guide to Google Postmaster Tools V2
How to debug DMARC authentication failure and alignment issues?
A simple guide to DMARC, SPF, and DKIM
Why your emails are getting a 'DMARC verification failed' error
Why does DMARC authentication fail when SPF and DKIM pass, and how can it be fixed?
Why does Google Postmaster Tools show compliance issues when email authentication is properly set up?
Why are some emails failing DMARC checks even with correct SPF and DKIM alignment, and how can I troubleshoot it?
