Why is DKIM failing in Hotmail but passing in Gmail?

Email marketer from Email Marketing Tips Forum suggests the possibility of regional DNS propagation issues. Some DNS servers used by Hotmail might not have fully propagated the DKIM record changes, while Gmail's DNS servers might be up-to-date. This can lead to DKIM passing in Gmail but failing in Hotmail.

Email marketer from Email Deliverability Blog responds that different email providers use varied DKIM validation algorithms. Use email testing tools specific to each provider to diagnose issues. Hotmail might require stricter adherence to the DKIM standard than Gmail.

Marketer from Email Geeks suggests removing any wildcard DKIM records as they may cause issues, and to recheck the DKIM configuration.

Email marketer from EmailGeeks Forum explains that Hotmail might be modifying the email content in transit, which can invalidate the DKIM signature. This is less common with Gmail, potentially explaining why DKIM passes there but fails in Hotmail.

Email marketer from StackExchange explains that Gmail might be more forgiving or have different DKIM validation rules than Hotmail/Outlook. It could also be related to how the DKIM record is interpreted or specific implementation differences in how each provider handles DKIM checks.

Email marketer from Quora suggests that if the email is being forwarded, it may be altering the headers or content, causing the DKIM signature to break. Hotmail may be more sensitive to forwarded emails, leading to DKIM failures, whereas Gmail might be more tolerant.

Email marketer from Reddit shares that differences in DKIM validation between email providers might occur because some providers are more strict about SPF and DKIM alignment. Hotmail could be more sensitive to these alignment checks, while Gmail might be more lenient if the DKIM signature itself is valid, even if SPF alignment is not perfect.

Email marketer from MailPoet shares that the key size of the DKIM record can affect validation. Hotmail may have different requirements or limitations regarding key size compared to Gmail. Ensure that the key size meets the recommended standards and is compatible with both providers.

Email marketer from Email Marketing Software Reviews shares that the presence of specific characters or encoding issues within the email's content can cause DKIM verification to fail. Hotmail might be more sensitive to these issues than Gmail.

Email marketer from Email Optimization Blog responds that some email providers, like Hotmail, might integrate DKIM checks more closely with their spam filters. If other elements in the email trigger the spam filter, the DKIM check might be stricter. Gmail's spam filtering might not weigh DKIM as heavily if other factors are present.

Expert from Email Geeks suggests checking for DNS issues where Microsoft can't see the DKIM record, or content issues where Microsoft modifies the email content before checking the signature.

Expert from Word to the Wise responds that Hotmail/Outlook might be more sensitive to sender reputation. If your IP address or domain has a poor reputation, Hotmail may be more likely to fail DKIM checks as an additional layer of scrutiny, while Gmail might weigh reputation less heavily.

Expert from Spamresource.com explains that DKIM validation is ultimately up to the receiver. Each provider sets its own policies for what constitutes a passing or failing DKIM result and how heavily it factors into their spam filtering decisions.

Expert from Email Geeks explains that Microsoft's DKIM signatures don't always verify correctly using OpenDKIM and it might be an interoperability problem.

Documentation from RFC 6376, the DKIM standard, explains that variations in interpreting the standard by different email providers can lead to inconsistencies. Issues like canonicalization, header field handling, and signature processing can differ, causing DKIM failures in some environments but not others.

Documentation from Port25 explains that DKIM failures can be due to incorrect selector usage or DNS misconfigurations. It also highlights that testing with different providers using the same configuration helps identify if the issue is on the sender's end or the receiver's end.

Documentation from Microsoft explains that DKIM failures can occur if the message content is altered in transit, the DKIM signature is invalid, or the DKIM record is not properly configured in the DNS settings. Also, it can be caused by a DNS propagation issue if the DNS settings are not updated across the global DNS servers.

Documentation from OpenDKIM explains that interoperability issues can arise if the DKIM implementation on the sending server (e.g., using OpenDKIM) has compatibility issues with the DKIM validation on the receiving server (e.g., Hotmail). This can be due to differences in the interpretation of the DKIM standard or bugs in either implementation.

Documentation from DMARC.org emphasizes the importance of consistent and correct DKIM implementation. The documentation highlights that proper DNS record setup, key management, and signature generation are crucial for DKIM validation. Differences in these implementations can cause DKIM failures on some platforms and not others.