Why are Microsoft Office 365 DKIM signatures failing and how to fix it?

Email marketer from ProofPoint explains that monitoring a domain using DMARC reports provide insight into DKIM failures and authentication issues. He suggests using DMARC reports to identify the sources of DKIM failure, and then work to resolve these failures at the source.

Email marketer from Mailjet advises that proper DKIM key management is essential for maintaining email authentication. They suggest regularly auditing your DKIM keys, monitoring for any signs of compromise, and having a plan in place for quickly rotating keys if necessary.

Email marketer from Reddit shares their experience after migrating to Office 365, they encountered DKIM failures due to incorrect DNS settings. They advise carefully reviewing the MX, SPF and DKIM records provided by Microsoft and ensuring they are accurately entered into your domain's DNS settings.

Email marketer from SendGrid explains that DKIM alignment, as part of a DMARC policy, is crucial for ensuring that emails pass authentication checks. They suggest configuring your DKIM signature to align with the domain used in the 'From' address to improve deliverability.

Email marketer from Spiceworks forum says a common reason for DKIM failures in Office 365 is due to mail flow configurations, especially when using third-party email security gateways. He recommends ensuring that the gateway is correctly configured to pass DKIM signatures without modification.

Email marketer from Email Geeks notes that in Office365, the Envelope-Sender address is showing on behalf of the actual sender's name/email, despite correct DKIM configuration, and that some users report outbound emails from Office 365 are not being signed correctly.

Email marketer from Microsoft Community forum says to check transport rules in Office 365 as they may be modifying emails and breaking the DKIM signature. He suggests reviewing any rules that might be adding disclaimers or altering the message body.

Email marketer from StackExchange explains that DKIM verification failures can occur when emails are forwarded, as the forwarding server may modify the email content, invalidating the DKIM signature. They recommend implementing SPF and DMARC in addition to DKIM to mitigate these issues.

Email marketer from Email Geeks shares an issue where DKIM signatures from Office365 implemented with a "n=1024,..." tag are failing in 50-60% of cases.

Email marketer from EasyDMARC explains that if a DKIM DNS record is invalid or missing, the DKIM signature is not valid. He suggests checking and fixing DNS records.

Email marketer from Neil Patel Blog shares that DKIM failures can significantly impact email deliverability, leading to messages being marked as spam. They recommend regularly monitoring DKIM reports and working with your email service provider to troubleshoot any issues.

Expert from Word to the Wise explains that DKIM failures often occur after migrating to Microsoft 365 due to DNS configuration errors. Double-check that your TXT record is set up correctly. The selector value, the domain, and the public key value must match what Microsoft has provided.

Expert from Email Geeks suspects that updating to the latest version of OpenDKIM would fix the algorithm incompatibility issue.

Expert from Email Geeks clarifies that outbound emails from Office365 may not necessarily be incorrectly signed, but instead use an algorithm that doesn't interoperate with OpenDKIM.

Expert from Word to the Wise explains that using too small of a key for DKIM can cause email deliverability issues. Upgrading to a key size of 2048 bits is recommended to align with modern security standards. You should also check your DMARC alignment.

Expert from Email Geeks shares bewilderment that Microsoft is adding an 'authentication results' header about the authentication at the receiving server.

Expert from Email Geeks explains that OpenDKIM consistently fails to verify DKIM signatures from Microsoft due to an interoperability issue between OpenDKIM and Microsoft's DKIM version, where they don't speak the same crypto.

Documentation from Google explains that if a DKIM signature fails, it can be because of DNS issues, problems with the signing process, or invalid characters. It suggests that you check and make sure that the DNS record is valid, and to retry sending a new test email. If the issue persists, you may have to regenerate the DNS record.

Documentation from RFC Editor specifies that the DKIM standard requires implementations to correctly handle various header fields and signature algorithms. The standard outlines potential reasons for signature verification failures, and provides guidance for robust DKIM implementation.

Documentation from AuthSMTP explains that common DKIM record errors involve syntax errors in the DNS record, incorrect key values, and special characters. They advise double-checking the record for any typos and ensuring it conforms to the DKIM standard.

Documentation from Microsoft Learn explains that common DKIM issues with Office 365 often stem from improper configuration, DNS propagation delays, or key size limitations. They advise verifying the DNS records are correctly published, waiting for propagation, and ensuring the key size meets Microsoft's requirements (at least 1024 bits).

Documentation from dmarcian explains DKIM troubleshooting steps include verifying the DKIM selector, ensuring the public key matches the private key, and confirming the DKIM signature is correctly formed in the email header. They also suggest using online DKIM validators to check for errors.

Documentation from GlobalSign outlines that DKIM best practices includes regularly rotating DKIM keys, using a strong key length (2048 bits recommended), and monitoring your domain's reputation. They emphasize the importance of a proactive approach to maintaining DKIM security.