How do I interpret SpamAssassin DKIM test results and troubleshoot DKIM signature issues?

Email marketer from EmailOnAcid describes that some DNS providers have limitations on the length of TXT records, potentially truncating the DKIM record and causing verification failures. Splitting the DKIM record into multiple TXT records (if supported by the DNS provider) can resolve this issue.

Email marketer from GlockApps explains that using an insufficient DKIM key size (e.g., less than 1024 bits) can lead to DKIM failures. Using a key size of at least 2048 bits is recommended for better security and compliance with modern email standards.

Email marketer from Litmus shares that a previewing tool can display the headers that can be useful in troubleshooting DKIM issues. Sending test email to these tools can let you copy the headers, and inspect if the DKIM signature is valid.

Email marketer from Reddit suggests that the DKIM record might not be fully propagated across all DNS servers. Even if it appears correct from your location, some servers might still have outdated information. Using online tools to check DKIM records from multiple locations can confirm full propagation.

Email marketer from Stackoverflow highlights that an email being forwarded can invalidate the DKIM signature. The forwarding server might alter headers, causing the signature to no longer match the email's content. Checking if the email has been forwarded is crucial.

Email marketer from Mailhardener shares that a common issue is incorrect DNS configuration, leading to failed DKIM checks. This includes typos in the TXT record, incorrect selector usage, or problems with the public key itself. Suggests verifying the DNS record and comparing it to the key used for signing.

Email marketer from MXToolbox explains that using the MXToolbox DKIM record lookup tool can help identify common errors in the DKIM record, such as incorrect syntax or invalid characters. Copying the DKIM selector and domain into the tool will confirm it is valid.

Email marketer from Postmark shares that failing domain alignment can cause DKIM failures. DKIM passes only if the domain in the 'From' header matches the domain used for signing. Ensuring proper alignment is crucial for passing DKIM checks.

Expert from SpamResource explains that DKIM failures can occur if the signing domain does not match the domain in the From header, or if the message content is modified in transit after signing. It also notes that issues can arise from problems in the DKIM record itself, such as incorrect syntax or missing selectors.

Expert from Word to the Wise highlights that DKIM is essential for DMARC alignment and achieving 'Pass' results. It emphasizes the importance of having a valid DKIM signature that aligns with the domain used in the 'From' header, in order to improve email deliverability and authentication.

Expert from Email Geeks explains the DKIM SpamAssassin test. The `DKIM_SIGNED` rule means the email has a DKIM-Signature header. The `DKIM_INVALID_DKIM` rule means that the DKIM signature is not valid.

Expert from Email Geeks shares a tool to investigate DKIM issues. Suggests sending an email to aboutmy.email to get more information about the DKIM signature and a shareable link for further analysis.

Documentation from RFC Editor shares that the wrong choice or implementation of DKIM canonicalization algorithms can invalidate the signature. The header and body canonicalization methods must be handled correctly during signing and verification.

Documentation from SpamAssassin Wiki explains that a DKIM_SIGNED test indicates the presence of a DKIM signature header. A DKIM_INVALID test (or similar) indicates a problem with the signature's validity. These tests alone do not guarantee spam classification but contribute to the overall score.

Documentation from OpenDKIM Wiki shares using the OpenDKIM tools to perform manual DKIM signing and verification tests can help isolate the problem. This involves crafting test emails and using the command-line tools to sign and verify the DKIM signature. Looking at the verbose output provides detailed information about the signing and verification process.

Documentation from GitHub explains that temporary DNS resolution failures can cause DKIM verification issues. Network connectivity problems or DNS server unavailability can lead to transient DKIM failures, which may resolve themselves. Checking DNS server status and network connectivity is important.

Documentation from ReturnPath shares that while it is not specific to DKIM, poor sender reputation may still send your emails to spam. Reputation is based on many things from spam complaints, email volume and more. Highlighting why good email practice is important.