Why is DKIM failing at some ISPs but not others, and how can I fix it?

Email marketer from Return Path says to check if the sending practices and IPs match the authentication (DKIM, SPF, DMARC) of your emails. Discrepancies or inconsistencies might cause failures at certain ISPs with stricter policies.

Email marketer from Stack Overflow shares that checking for common configuration errors, like incorrect selector names or typos in the DNS TXT record, is a key troubleshooting step. Provides tools to help with DKIM record validation to verify the correctness of the DNS settings.

Email marketer from Email on Acid says that DKIM failures happen when the signature doesn't match the content. It often involves the encoding, signature process, or DNS issues. Test DKIM with different email clients and mailbox providers to help isolate the problem.

Email marketer from SuperOffice says to make sure that your sender reputation and email practices are maintained. This involves having appropriate DNS configurations set up, including the DKIM and SPF records to ensure that they match with your sending domains to prevent any discrepancies.

Email marketer from Reddit suggests that DKIM failing only for Yahoo might be due to Yahoo's stricter policies and DNS configuration requirements. Check for proper key length and ensure the DNS records fully propagate across all Yahoo servers.

Email marketer from Mailjet explains that DKIM failures can occur if the email content is altered in transit between sending and receiving servers. ISPs may modify headers or footers, invalidating the DKIM signature. Suggests using end-to-end encryption (TLS) and avoiding unnecessary intermediaries.

Email marketer from SparkPost supports ensuring that the 'header from' domain matches your DKIM and SPF records. Misalignment might trigger DKIM failures, and DMARC policies at ISPs may cause problems with your email delivery.

Email marketer from GlockApps supports using online tools to validate that the DKIM DNS record is published correctly and that the DKIM key is valid. Verifying that the record and key are functional is important in diagnosing DKIM problems.

Expert from Email Geeks notes Google has extensive data from 8.8.8.8, allowing them to identify which authoritative servers are not functioning correctly and potentially cache positive responses.

Expert from Email Geeks shares that intermittent DKIM failures seen by some ISPs are often due to only some DNS servers being configured correctly. Suggests it's likely a broken authoritative DNS server in this case since multiple ISPs are affected and to use testing to confirm.

Expert from Word to the Wise explains that an incorrect DKIM setup is a significant cause of DKIM failures and that this may involve DNS record syntax errors, incorrect public key placement or a mismatch between the selector used in the DKIM signature and the one specified in the DNS record. The receiving ISPs may vary with the level of strictness in applying those checks. They explain that some ISPs might validate DKIM signatures based on older or cached records, while others query the DNS each time. If changes to DNS records aren't reflected quickly, or if there are inconsistencies, it can lead to DKIM authentication failures at certain ISPs, but not others.

Expert from Spamresource.com explains that one of the primary reasons for DKIM failing at some ISPs but not others comes down to inconsistencies in DNS record propagation or caching. Some ISPs may be using outdated DNS servers or have different caching intervals, leading to failures in DKIM authentication if they're not retrieving the latest DKIM records. They go on to say that ensuring that the DKIM records are correctly configured and propagated across all DNS servers is the critical issue. This involves verifying the DKIM key's correctness and making sure the DNS records are properly formatted. They also explain that some ISPs are overly sensitive to minor encoding errors, specifically those related to MIME formatting or header encoding. Even slight variations from the expected format can cause DKIM validation failures on these ISPs.

Expert from Email Geeks and Marketer from Email Geeks suggest the Azure DNS settings may be causing issues due to a wildcard DNS entry and incorrect NS records. Removing the wildcard might improve things. They recommend checking DNS configuration using tools like XNND and DNS Viz. The main issue was identified as DNS misconfiguration.

Expert from Email Geeks explains that DKIM failures are unlikely due to return path or sending domain unresolvability. The issue may be with the domain where the DKIM public key is located. Common cause is DNS misconfiguration.

Documentation from dmarcian details that inconsistent character encoding can cause DKIM failures. Different ISPs may handle character sets differently, leading to hashing mismatches. Standardizing character encoding (e.g., UTF-8) across all emails can mitigate this issue.

Documentation from Google explains that DKIM failures at specific ISPs may indicate DNS propagation issues. Some ISPs might be using outdated DNS records, while others have updated records. Resolving requires ensuring DNS records are correctly configured and propagated.

Documentation from Microsoft indicates that a DKIM failure can occur if the key length is insufficient or not supported by the receiving ISP. Ensures the DKIM key is sufficiently large (e.g., 2048 bits) and compatible with major ISP requirements.

Documentation from AuthSMTP says that if email signatures are not properly implemented, it could lead to DKIM failures. This involves generating the DKIM key, publishing it in your DNS records, and making sure the sending server is configured correctly.