Summary
DKIM errors during double DKIM implementation arise from a confluence of factors including DNS misconfigurations, key mismatches or invalid keys, message content alterations, key size limitations, and email server misconfigurations. Addressing these errors necessitates validating DNS records, ensuring proper key sizes, preventing content changes after signing, aligning DKIM with DMARC, and cautiously managing key rotations, alongside thorough planning and testing.
Key findings
- DNS Issues: Incorrectly configured DNS records and propagation delays are frequent sources of DKIM problems.
- Content Alteration: Modifications to the email content after the DKIM signature is applied invalidate the signature.
- Server Misconfiguration: Misconfigurations on sending servers, particularly with forwarding and auto-responses, can disrupt DKIM.
- Key Mismatch: Mismatch in the selector values used in DNS and those used when signing can lead to errors.
- Key Size: Incorrect or unsupported key sizes can cause DKIM failures.
- DKIM-DMARC Alignment: The DKIM signing domain must align with the 'From:' address domain for DMARC validation.
- First Key: When implementing double DKIM, fix the first key before adding the second.
Key considerations
- Diagnostic Tools: Use tools to validate DNS records, check for proper signing, and diagnose issues.
- Content Integrity: Prevent changes to email content after the DKIM signature is applied.
- Transition Planning: When rotating DKIM keys, maintain the old key until the new one is fully propagated.
- Alignment: Ensure the DKIM signing domain aligns with the 'From:' address domain.
- Email Headers: Checking email headers can help identify where DKIM checks have failed.
- Email Validators: Use Email Validators to ensure configurations are correct.
What email marketers say
9 marketer opinions
DKIM errors during double DKIM implementation stem from a variety of sources, primarily related to DNS configuration, email content modification, and server misconfigurations. Correct setup of DNS records, preventing content changes after signing, and ensuring proper server configuration are crucial. Understanding the interplay between DKIM and DMARC is also essential for preventing authentication failures.
Key opinions
- DNS Errors: Incorrectly configured DNS records, particularly with multiple DKIM keys, are a common cause of DKIM failures.
- Content Modification: Email content being altered after the DKIM signature is applied invalidates the signature.
- Server Misconfigurations: Sending server misconfigurations, especially with forwarding and auto-responses, can disrupt DKIM.
- DKIM-DMARC Alignment: The DKIM 'd' parameter must align with the 'From:' header domain for DMARC to pass.
- Email Forwarding Issues: Email Forwarding can cause DKIM failures if the content or headers are altered after the DKIM signature is applied.
Key considerations
- Diagnostic Tools: Utilize diagnostic tools to validate DNS records and DKIM setup.
- DKIM Validators: Utilize DKIM Validators to ensure the DKIM record itself is valid
- Content Integrity: Ensure outgoing mail servers do not modify email content after DKIM signing.
- Transition Planning: When rotating DKIM keys, maintain old keys until new ones propagate.
- Domain Alignment: Verify the DKIM signing domain aligns with the 'From:' address domain.
- Full email path: Examine the full email path to identify where changes are occurring and to ensure all hops preserve the original DKIM signature.
Marketer view
Email marketer from GMass says understanding the alignment between DKIM and DMARC is essential. If the 'd' parameter (domain) in the DKIM signature does not match the domain in the 'From:' header, DMARC can fail, even if DKIM passes. Ensures domains align.
24 Feb 2024 - GMass
Marketer view
Email marketer from Reddit suggests that DKIM failures can be caused by intermediate mail servers altering the message content, especially headers. The advice is to examine the full email path to identify where changes are occurring and to ensure all hops preserve the original DKIM signature.
16 Oct 2024 - Reddit
What the experts say
3 expert opinions
DKIM errors during double DKIM implementation can arise from problems with the initial DKIM key, improperly configured DNS records, or key size limitations. Addressing these issues involves validating DNS configurations, ensuring correct key sizes, and focusing on fixing existing problems before adding a second DKIM key.
Key opinions
- Initial Key Issues: Problems with the first DKIM key in a double DKIM setup should be resolved before adding the second key.
- DNS Misconfiguration: Improperly formatted or configured DNS records are a frequent cause of DKIM issues.
- Key Size Limitations: Exceeding key size limits supported by email receivers can lead to DKIM failures.
Key considerations
- MTA Verification: Check which Mail Transfer Agent (MTA) is being used, as this may influence the source of errors.
- DNS Validation: Use online tools to validate DKIM DNS records and ensure proper key and selector setup.
- Key Size Compliance: Ensure that the DKIM key size is within the limits supported by common email receivers.
Expert view
Expert from Email Geeks shares that from the shared header there seems to be a problem with the first key, suggesting to fix that before adding the second key, and asks which MTA is being used.
20 Nov 2021 - Email Geeks
Expert view
Expert from Word to the Wise shares that DKIM errors sometimes arise because of key size limitations. Email receivers might have limitations on the size of DKIM keys they support. Using a key size that exceeds these limits will result in a DKIM failure. Ensure the key size is within acceptable bounds for common email receivers.
12 Sep 2021 - Word to the Wise
What the documentation says
3 technical articles
DKIM errors during double DKIM implementation are caused by various factors including DNS misconfiguration, key mismatches, message alteration during transit, incorrect key sizes, canonicalization algorithm issues, and problems with message body handling. Ensuring both keys are valid, correctly configured in DNS, and properly rotated, alongside careful planning and testing, are crucial to prevent these errors.
Key findings
- DNS Issues: DNS misconfiguration and propagation delays contribute significantly to DKIM failures.
- Key Validation: Ensuring both DKIM keys are valid is essential in a double DKIM setup.
- Message Alteration: Changes to email content during transit can invalidate DKIM signatures.
- Algorithmic Issues: Problems with canonicalization algorithms and message body handling can cause DKIM errors.
- Key Size: Incorrect Key sizes are common issues in double DKIM.
Key considerations
- Careful Planning: Thorough planning and testing are necessary during key rotation and double DKIM implementation.
- Configuration Verification: Double-check the configuration of DNS records to ensure they are accurate and up-to-date.
- Message Integrity: Ensure that email content remains unaltered after signing to prevent signature invalidation.
Technical article
Documentation from DKIM.org addresses key rotation, suggesting planning and testing and describes that when implementing double DKIM, ensuring that both keys are valid and correctly configured in DNS is crucial. Issues often arise from DNS propagation delays or configuration errors in the DNS records for the second key.
5 Mar 2024 - dkim.org
Technical article
Documentation from RFC 6376 details common DKIM problems including incorrect key sizes, issues with canonicalization algorithms, and problems related to message body handling (e.g., line wrapping or character encoding changes).
14 Mar 2024 - ietf.org
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