What causes DKIM errors during double DKIM implementation and how can they be fixed?
Summary
What email marketers say9Marketer opinions
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.
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.
Email marketer from StackOverflow explains that one common issue is the email content being modified by the sending server after the DKIM signature is generated. Ensure any outgoing mail server is configured to not alter email content after DKIM signing.
Email marketer from SparkPost recommends that when rotating DKIM keys or implementing a double DKIM setup, ensure a smooth transition by keeping the old key active until all email systems recognize the new key. This prevents intermittent failures during the rollout.
Email marketer from EasyDMARC discusses DKIM failure causes, noting that common causes include modifications to the email content after signing, incorrect key sizes, and issues related to the email's character encoding. They advise checking the email headers to identify where the DKIM check failed.
Email marketer from AuthSMTP suggests one of the more common issues are from email forwading causing DKIM breaks. Email forwarders that change the message content or headers will invalidate the DKIM signature, leading to delivery issues.
Email marketer from Email on Acid says debugging DKIM involves checking the DNS records for correctness and validating that the signing process is correctly implemented on the email server. Tools like DKIM validators can help identify issues with the DKIM record itself.
Email marketer from MailEnable Forums shares that DKIM errors can sometimes occur due to misconfigurations on the sending server, particularly with how the DKIM signing process interacts with email forwarding or auto-responses. Checking server configurations and ensuring DKIM is properly enabled for all outgoing mail is recommended.
Email marketer from Mailhardener explains that DKIM problems frequently stem from DNS configuration errors, particularly when setting up multiple DKIM records. They recommend using diagnostic tools to check the DNS records and ensuring that the selector values match the key being used.
What the experts say3Expert opinions
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.
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.
Expert from Spam Resource explains that DKIM issues are often related to improperly formatted or configured DNS records. Ensuring the DNS TXT record for DKIM is correctly set up with the proper key and selector is crucial. They suggest using online tools to validate the DKIM record.
What the documentation says3Technical articles
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.
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).
Documentation from Google explains that DKIM signature verification failures can arise from issues like DNS misconfiguration, key mismatch, or message alteration during transit. Incorrect DNS records or changes to the email content after signing can invalidate the DKIM signature.