Summary
A missing DKIM DNS TXT record for a domain that is actively attempting to sign its emails with DKIM can severely impact email deliverability. While some might assume it's equivalent to not signing at all, the scenario of a deliberate signing attempt coupled with a missing public key can sometimes lead to more negative scrutiny from mailbox providers.
Key findings
- Authentication failure: When a DKIM signature is present on an email but the corresponding public key is not found in the DNS TXT record, the signature validation fails. This effectively renders the email unauthenticated by DKIM.
- Equal to no signing: From a technical authentication standpoint, a DKIM failure (due to a missing TXT record or any other reason) is often treated the same as if the email had no DKIM signature at all. Both scenarios result in a fail result for DKIM authentication.
- Reputation impact: Mailbox providers rely on authentication protocols like DKIM to establish sender legitimacy and prevent spoofing. A consistent failure to validate DKIM signatures can negatively affect your sender reputation.
- DMARC consequences: If you have a DMARC policy in place, a DKIM failure (even if SPF passes) will cause the email to fail DMARC alignment unless the SPF authentication also passes and aligns. This can lead to emails being quarantined or rejected based on your DMARC policy. More information on how DMARC failures affect deliverability is available.
Key considerations
- Intent vs. outcome: While you intend to sign your emails, the absence of the public key means the intent isn't fulfilled, and the outcome is an unauthenticated email.
- Spam filtering: Many mailbox providers, especially those with stringent authentication requirements like Google and Yahoo, heavily weigh authentication in their spam filtering decisions. A missing or misconfigured DKIM record can result in emails being sent to the spam folder or even being rejected outright. This is detailed in various sources, including Digital Showroom's article on DNS impact on deliverability.
- Machine learning: Advanced spam filters employ machine learning algorithms that might detect a discrepancy between an email claiming to be DKIM signed (having a DKIM header) and the failure to validate that signature. This inconsistency could potentially be flagged as suspicious behavior.
- Troubleshooting priority: If emails are being signed but the public key is missing, resolving the DNS TXT record issue should be a top priority to ensure proper email authentication and improve deliverability.
What email marketers say
Email marketers often face the immediate impact of deliverability issues when their emails fail authentication. While the technical nuances of DKIM failures might be complex, the practical outcome for marketers is clear: reduced inbox placement. They frequently observe a direct correlation between authentication status and whether their messages reach the primary inbox or are diverted to spam folders.
Key opinions
- Direct impact: Marketers frequently report that emails failing DKIM (or other authentication checks) are very likely to be sent to spam or outright rejected by major mailbox providers, such as Google and Yahoo.
- No discernible difference: Many marketers find that from a deliverability perspective, a DKIM failure due to a missing public key is practically indistinguishable from not having a DKIM signature at all.
- Beyond the technical: While technically a DKIM failure is a DKIM failure, some believe that advanced machine learning filters might interpret the attempt to sign (with a header present) followed by a verification failure more negatively than a complete absence of a DKIM signature, though concrete evidence is often anecdotal.
- Authentication is paramount: With recent updates from major providers emphasizing email authentication, ensuring all authentication protocols like SPF, DKIM, and DMARC are correctly configured is critical for maintaining email deliverability.
Key considerations
- Monitor performance: Marketers should diligently monitor their email deliverability metrics and DMARC reports to quickly identify and address any DKIM authentication failures.
- Prioritize fixes: A missing DKIM DNS TXT record is a critical issue that must be fixed promptly, as it undermines the entire purpose of implementing DKIM. Learn how to fix common DKIM errors.
- Verify configuration: Regularly verify that DKIM DNS TXT records are correctly published and accessible. Misconfigurations are a common cause of deliverability problems, as noted by Kickbox in their DNS deliverability guide.
- Holistic approach: Even with DKIM issues, SPF and DMARC can still influence deliverability. However, aiming for all three to pass is the best practice for optimal inbox placement.
Marketer view
Marketer from Email Geeks suggests that Google is highly likely to send messages to spam or start deferring/bouncing them if DKIM authentication fails. There isn't much evidence to suggest if it's worse than not signing at all.
Marketer view
Marketer from Email on Acid highlights that a DKIM signature helps mailbox providers verify the sender and prevent phishing attacks and email spoofing. A missing key renders this protection ineffective.
What the experts say
Experts in email deliverability emphasize that proper authentication is foundational to inbox placement in today's email ecosystem. While the technical specifics of a missing DKIM TXT record can be debated, the consensus points to a significant negative impact. The core message from experts is that any failure in a recognized authentication protocol diminishes sender trust and increases the likelihood of mail being treated as suspicious.
Key opinions
- Authentication parity: Many experts agree that a message with a DKIM signature that fails validation (e.g., due to a missing TXT record) is treated similarly to a message that never had a DKIM signature in the first place, from the perspective of simply passing authentication.
- No pass is a problem: For deliverability, only a 'pass' on authentication truly counts. Anything else, whether a failure or absence, contributes negatively to the email's legitimacy score. This is relevant to concepts such as DKIM's absence when SPF passes.
- Holistic view by receivers: While DKIM failure is technical, receiving systems consider many factors. A DKIM failure, especially when combined with other suspicious signals, contributes to a lower overall trust score.
- Evolving policies: Major mailbox providers (like Yahoo and Google) have recently increased their emphasis on strong email authentication, making it increasingly difficult for unauthenticated or improperly authenticated emails to reach the inbox. This includes the crucial role of authentication protocols.
Key considerations
- Configuration accuracy: Ensuring the DKIM DNS TXT record is precisely correct and published is paramount. Even minor errors can lead to validation failures, impacting deliverability. Incorrect configuration is often a cause for emails ending up on a blocklist.
- Proactive monitoring: Continuous monitoring of DKIM validation status through DMARC reports and deliverability tools is essential to catch and rectify missing or incorrect DNS records promptly.
- Negative signals: While a DKIM failure might not be worse than no signature in all cases, the presence of a signature that fails can be interpreted as a negative signal by sophisticated anti-spam systems.
- DMARC enforcement: For domains with DMARC policies set to quarantine (p=quarantine) or reject (p=reject), a DKIM failure due to a missing TXT record will directly lead to the specified policy action, severely impacting deliverability. This highlights the importance of turning on DKIM correctly.
Expert view
Expert from Email Geeks reiterates that from an authentication perspective, a DKIM failure, regardless of its specific cause, results in the email being considered 'unsigned,' similar to having no DKIM signature present at all.
Expert view
Expert from SpamResource states that consistent authentication failures, like a missing DKIM TXT record, degrade sender reputation over time, leading to poorer inbox placement and increased spam classification.
What the documentation says
Official documentation and industry standards consistently highlight DKIM as a crucial email authentication method. They emphasize that the core functionality relies on a publicly accessible DNS TXT record containing the public key. Without this record, the cryptographic verification process cannot occur, rendering the signature invalid and compromising the email's authenticity in the eyes of recipient servers.
Key findings
- Validation process: DKIM validation involves the recipient server querying the sender's DNS for a TXT record containing the public key associated with the DKIM signature in the email header. A missing record prevents this fundamental step.
- Cryptographic failure: The absence of the public key means the recipient server cannot decrypt and verify the email's cryptographic signature, leading to a definitive DKIM authentication failure.
- Standard compliance: For DKIM to function as intended per RFCs, the public key MUST be published in the DNS TXT record. Failure to do so means non-compliance with the standard.
- Trust and reputation: Email authentication protocols like DKIM are designed to build sender trust and improve domain reputation. A consistent failure breaks this trust and can lead to a degraded reputation.
Key considerations
- Mandatory element: The DKIM public key in DNS is not optional; it is a required component for successful DKIM authentication.
- Direct rejection risk: While some systems might still deliver emails without DKIM, many strict setups (especially those enforcing DMARC with a reject policy) will directly reject emails that fail DKIM due to a missing public key.
- Impact on DMARC: Documentation from organizations like Email Industries confirms that email authentication records like DKIM play a crucial role in preventing email spoofing and improving deliverability. DMARC relies on either SPF or DKIM to pass and align, so a DKIM failure means one less chance for DMARC to pass.
- Ease of fix: Correcting a missing DKIM DNS TXT record is a straightforward DNS configuration task, making it an easily fixable issue that can significantly improve deliverability.
Technical article
Documentation from Mailgun states that email authentication protocols like SPF, DKIM, and DMARC are crucial for protecting emails from spoofing and significantly improving deliverability rates, by allowing recipients to verify sender identity.
Technical article
Documentation from Freshdesk support outlines that DKIM plays a crucial role in enhancing email security, establishing sender legitimacy, and ensuring better email deliverability through the reduction of spam and phishing attacks.
Related resources
11 resources
Related pages
How does the absence of DKIM affect email deliverability when SPF is passing and DMARC is aligned?
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A simple guide to DMARC, SPF, and DKIM
How to troubleshoot DMARC failures and their impact on email deliverability?
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