Summary
DMARC operates on an 'OR' logic principle, meaning an email passes DMARC authentication if either SPF or DKIM successfully authenticates and aligns with the 'From' domain. This fundamental design prevents configuring DMARC to reject emails solely when DKIM fails but SPF passes and aligns, as the passing SPF status inherently satisfies DMARC's requirements. A DMARC policy of `p=reject` only takes effect when both SPF and DKIM fail their respective alignment checks.
Key findings
- DMARC's OR Logic: DMARC authentication passes if either SPF or DKIM successfully authenticates and aligns with the 'From' domain. This 'OR' logic is fundamental to how DMARC evaluates email authenticity.
- SPF Precedence: If SPF successfully authenticates the sending server and its domain aligns with the 'From' domain, DMARC will pass the email. This occurs regardless of whether DKIM fails or is absent, effectively overriding any DKIM authentication issues for the DMARC outcome.
- Dual Failure for Rejection: A DMARC policy of `p=reject` will only be enforced and lead to an email being rejected if both SPF and DKIM fail their respective authentication and alignment checks against the 'From' domain.
- Unaligned SPF as an Option: While it is technically possible to intentionally unalign SPF or remove the SPF record to force a DMARC failure when DKIM fails, this approach is generally impractical for bulk mailers. Major mailbox providers often require SPF for deliverability, making deliberate unalignment or removal unfeasible.
- No Specific DMARC Tag: There is no specific DMARC tag or configuration option that allows for the rejection of emails solely based on a DKIM failure when SPF passes and aligns. The `adkim` tag, for instance, focuses on DKIM alignment, not on overriding SPF's DMARC pass.
Key considerations
- Understand DMARC Mechanics: It is crucial to grasp that DMARC operates on an 'OR' logic principle, meaning its primary goal is to ensure at least one authentication method, either SPF or DKIM, successfully aligns with the 'From' domain. It is not designed to selectively reject based on an individual authentication failure if the other method succeeds.
- Focus on Overall Deliverability: Instead of attempting to configure DMARC for specific, nuanced failure scenarios, prioritize robust and correct SPF and DKIM configuration across all your sending sources. This foundational approach is essential for consistent and reliable email deliverability.
- SPF Alignment is Key: Ensure your SPF record is correctly configured and that its authenticated domain aligns with your 'From' domain. A properly aligned SPF record will lead to a DMARC pass, irrespective of DKIM's status, and is vital for your email's reputation.
- DMARC Policy Impact: Your DMARC policy, particularly a `p=reject` policy, will only be activated and enforced when both SPF and DKIM authentication and alignment checks fail. A passing SPF alignment will always lead to a DMARC pass, overriding any DKIM failure.
- Avoid Deliberate Unalignment: Intentionally causing SPF alignment failures to achieve a DMARC reject due to a DKIM failure is not a recommended or practical strategy for legitimate email sending, especially to major mailbox providers like Google and Yahoo, who highly value SPF.
What email marketers say
11 marketer opinions
Contrary to some misconceptions, DMARC's operational framework dictates that an email passes its authentication check if either SPF or DKIM successfully validates and aligns with the 'From' domain. This means it is not possible to configure DMARC to reject emails solely when DKIM fails but SPF passes and aligns, as the passing SPF status inherently leads to a DMARC pass. A DMARC policy of p=reject will only be enforced and result in an email being rejected if both SPF and DKIM fail their respective authentication and alignment checks.
Key opinions
- DMARC Operates on OR Logic: DMARC is designed to pass an email if at least one of its underlying authentication mechanisms, SPF or DKIM, successfully authenticates and aligns with the 'From' domain. This 'OR' logic prevents a rejection when one method passes.
- SPF Alignment Leads to Pass: If an email successfully passes SPF authentication and achieves DMARC alignment with the 'From' domain, DMARC will inherently pass the email. This outcome occurs regardless of whether DKIM authentication fails or is not present for that email.
- Dual Failure for Rejection: A DMARC policy of p=reject is only enforced and leads to an email being rejected when both SPF and DKIM fail their respective authentication and DMARC alignment checks against the 'From' domain. A single failure is not sufficient if the other mechanism passes.
- No Specific Configuration Tag: There is no specific DMARC tag or configuration option that allows for the rejection of emails solely based on a DKIM failure when SPF passes and aligns. The adkim tag, for instance, focuses on DKIM alignment, but does not override DMARC's 'OR' logic.
- Unaligned SPF is Impractical: While it's theoretically possible to intentionally unalign SPF or remove the SPF record to force a DMARC failure when DKIM fails, this approach is generally not viable for legitimate senders. Many major mailbox providers require SPF for deliverability, making deliberate misconfiguration counterproductive.
Key considerations
- Understand DMARC's Core Logic: It is essential to recognize that DMARC functions on an 'OR' basis, where a passing DMARC result is achieved if either SPF or DKIM successfully authenticates and aligns. Attempting to force a DMARC rejection when one mechanism passes goes against its fundamental design.
- Prioritize Robust Setup: Focus on ensuring that both SPF and DKIM are correctly configured and aligned for all your legitimate sending sources. This holistic approach to email authentication is crucial for optimal deliverability and sender reputation, rather than trying to engineer specific failure scenarios.
- SPF Alignment is Paramount: Correct SPF configuration and alignment with your 'From' domain are vital. A properly aligned SPF record will lead to a DMARC pass, irrespective of DKIM's status, and is a strong indicator of legitimacy to receiving servers.
- DMARC Policy Enforcement: Remember that a DMARC policy of p=reject will only be applied if both SPF and DKIM authentication and alignment checks fail. If SPF passes and aligns, the reject policy will not be triggered solely due to a DKIM failure.
- Avoid Artificial Failures: Deliberately misconfiguring or removing SPF to force a DMARC rejection based on a DKIM failure is not a recommended or practical strategy. Such actions can negatively impact overall email deliverability and sender reputation, especially with major mailbox providers that rely on SPF for validation.
Marketer view
Marketer from Email Geeks responds that it is not possible to configure DMARC to reject on DKIM failure while SPF passes and aligns, because SPF alignment and authentication inherently lead to a DMARC pass.
14 Feb 2024 - Email Geeks
Marketer view
Marketer from Email Geeks suggests that if SPF is not desired for a DMARC pass, one could either unalign SPF or remove the SPF record entirely.
11 Apr 2024 - Email Geeks
What the experts say
3 expert opinions
It is not feasible to configure DMARC to reject emails solely when DKIM fails but SPF passes and aligns, because DMARC's foundational design dictates that a message passes if at least one of these authentication methods, SPF or DKIM, successfully authenticates and aligns with the 'From' domain. Consequently, a DMARC policy of p=reject will only be enforced when both SPF and DKIM fail their respective authentication and alignment checks.
Key opinions
- DMARC's 'OR' Logic: DMARC's design inherently uses an 'OR' logic, meaning a message passes authentication if either SPF or DKIM successfully validates and aligns with the 'From' domain. This prevents rejection when one method passes.
- SPF Pass Prevents Rejection: If an email successfully passes SPF authentication and achieves DMARC alignment, the email will pass DMARC, even if DKIM authentication fails. The passing SPF status is sufficient for DMARC compliance.
- Rejection Requires Dual Failure: A DMARC policy of p=reject is only enforced, and an email subsequently rejected, when both SPF and DKIM fail their respective authentication and DMARC alignment checks. A single failure is not enough to trigger rejection if the other mechanism passes.
- No Specific Reject Option: There is no specific DMARC tag or configuration that allows for the rejection of emails solely based on a DKIM failure when SPF passes and aligns. The protocol is not designed to differentiate this specific failure scenario for rejection.
- Unaligned SPF Is Impractical: While theoretically possible, intentionally unaligning SPF or removing the SPF record to force a DMARC failure when DKIM fails is generally not viable for bulk email senders. Many major mailbox providers require SPF for optimal deliverability.
Key considerations
- Grasp DMARC's Principles: It is essential to understand that DMARC's primary function is to confirm at least one authentication method-SPF or DKIM-successfully aligns with the 'From' domain. Attempts to force a rejection when one method passes go against this fundamental design.
- Focus on Comprehensive Setup: Prioritize correctly configuring both SPF and DKIM across all your legitimate sending platforms. A robust, holistic authentication setup is more effective for deliverability than trying to engineer specific failure scenarios.
- SPF Alignment is Crucial: Ensure your SPF record is accurately set up and aligns with your 'From' domain. A properly aligned SPF record will lead to a DMARC pass, regardless of DKIM's status, and significantly contributes to your email's trustworthiness.
- DMARC Policy Enforcement: A DMARC policy set to 'p=reject' will only be applied if both SPF and DKIM authentication and alignment checks fail. If SPF passes and aligns, the reject policy will not be triggered solely because DKIM failed.
- Avoid Intentional Misconfiguration: Deliberately unaligning or removing SPF to achieve a DMARC rejection when DKIM fails is not a practical or recommended strategy. Such actions can severely harm your email deliverability and sender reputation, especially with major mailbox providers.
Expert view
Expert from Email Geeks confirms that it is not possible to configure DMARC to reject on DKIM failure while SPF passes and aligns. They note that sending bulk mail to Google and Yahoo without SPF is not feasible, suggesting that deliberate SPF unalignment is an option, although many major senders like Intuit, Mailchimp, and Constant Contact already send with unaligned SPF, and it currently is not a significant filter metric.
2 Nov 2023 - Email Geeks
Expert view
Expert from Word to the Wise explains that DMARC is configured with a p=reject policy to reject emails that fail DMARC authentication. However, for a message to be DMARC compliant and avoid rejection, at least one identifier (SPF or DKIM) must pass authentication and alignment. Therefore, if SPF passes and aligns, DMARC will pass and the email will not be rejected, even if DKIM fails. Rejection only occurs when both SPF and DKIM fail to authenticate or fail alignment.
26 Oct 2024 - Word to the Wise
What the documentation says
5 technical articles
Attempting to configure a DMARC policy that rejects emails specifically when DKIM fails but SPF passes is not aligned with the DMARC standard. DMARC's fundamental design dictates that an email achieves a DMARC pass if either SPF or DKIM successfully authenticates and aligns with the 'From' domain. Consequently, a DMARC policy of p=reject will only be enforced when both SPF and DKIM fail their respective authentication and alignment checks, as a passing SPF alignment inherently satisfies DMARC's requirements.
Key findings
- DMARC's OR Logic: DMARC authentication passes if either SPF or DKIM successfully authenticates and aligns with the 'From' domain. This 'OR' logic is fundamental to how DMARC evaluates email authenticity.
- SPF Precedence: If SPF successfully authenticates the sending server and its domain aligns with the 'From' domain, DMARC will pass the email. This occurs regardless of whether DKIM fails or is absent, effectively overriding any DKIM authentication issues for the DMARC outcome.
- Dual Failure for Rejection: A DMARC policy of p=reject will only be enforced and lead to an email being rejected if both SPF and DKIM fail their respective authentication and alignment checks against the 'From' domain.
- Unaligned SPF as an Option: While it is technically possible to intentionally unalign SPF or remove the SPF record to force a DMARC failure when DKIM fails, this approach is generally impractical for bulk mailers. Major mailbox providers often require SPF for deliverability, making deliberate unalignment or removal unfeasible.
- No Specific DMARC Tag: There is no specific DMARC tag or configuration option that allows for the rejection of emails solely based on a DKIM failure when SPF passes and aligns. The adkim tag, for instance, focuses on DKIM alignment, not on overriding SPF's DMARC pass.
Key considerations
- Understand DMARC Mechanics: It is crucial to grasp that DMARC operates on an 'OR' logic, meaning its primary goal is to ensure at least one authentication method, either SPF or DKIM, successfully aligns with the 'From' domain. It is not designed to selectively reject based on an individual authentication failure if the other method succeeds.
- Focus on Overall Deliverability: Instead of attempting to configure DMARC for specific, nuanced failure scenarios, prioritize robust and correct SPF and DKIM configuration across all your sending sources. This foundational approach is essential for consistent and reliable email deliverability.
- SPF Alignment is Key: Ensure your SPF record is correctly configured and that its authenticated domain aligns with your 'From' domain. A properly aligned SPF record will lead to a DMARC pass, irrespective of DKIM's status, and is vital for your email's reputation.
- DMARC Policy Impact: Your DMARC policy, particularly a p=reject policy, will only be activated and enforced when both SPF and DKIM authentication and alignment checks fail. A passing SPF alignment will always lead to a DMARC pass, overriding any DKIM failure.
- Avoid Deliberate Unalignment: Intentionally causing SPF alignment failures to achieve a DMARC reject due to a DKIM failure is not a recommended or practical strategy for legitimate email sending, especially to major mailbox providers like Google and Yahoo, who highly value SPF.
Technical article
Documentation from IETF RFC 7489 explains that DMARC authentication requires either SPF or DKIM to pass and achieve DMARC alignment. If SPF passes and aligns successfully, the DMARC authentication will pass, regardless of whether DKIM fails. Therefore, it is not possible to configure a DMARC policy to reject emails solely when DKIM fails if SPF passes and aligns for DMARC, because the passing SPF alignment would lead to a DMARC pass. Rejection only occurs if both SPF and DKIM fail their respective DMARC alignment checks.
13 Oct 2023 - dmarc.org, IETF RFC 7489
Technical article
Documentation from Google Postmaster Tools implicitly states that DMARC allows senders to specify an action (none, quarantine, reject) if an email fails DMARC authentication. For an email to fail DMARC, both SPF and DKIM must fail DMARC alignment. If SPF passes and aligns with the organizational domain in the From: header, DMARC will pass, irrespective of the DKIM result. Therefore, configuring DMARC to reject solely on DKIM failure when SPF passes and aligns is not a standard DMARC behavior, as a passing SPF alignment would satisfy DMARC.
24 Oct 2021 - Google Postmaster Tools Help
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