Why are my plane ticket emails going to spam in Hotmail when DKIM fails, but passes in Gmail?

Email marketer from StackOverflow mentions that DMARC policies can affect how different email providers handle DKIM failures. If DMARC is set to 'reject' or 'quarantine' and DKIM fails, Hotmail is more likely to send the email to spam, whereas Gmail might be more lenient.

Email marketer from Mailchimp explains that maintaining a good sender reputation is crucial for email deliverability. They suggest monitoring your sender score and addressing any issues that could be affecting your reputation, such as high bounce rates or spam complaints. Hotmail might be more sensitive to sender reputation than Gmail.

Email marketer from Campaign Monitor recommends maintaining a clean email list by regularly removing inactive subscribers and those who have unsubscribed. Sending emails to a large number of invalid or inactive addresses can damage sender reputation and lead to deliverability issues.

Email marketer from an Email Marketing Forum suggests that certain words or phrases commonly associated with spam or phishing (e.g., urgent travel offers, lottery wins) can trigger spam filters. They advise reviewing the email content for potentially problematic keywords.

Email marketer from GMass recommends using a dedicated IP address to send emails, especially if sending large volumes. This allows senders to build their own reputation with email providers, which can improve deliverability. Shared IP addresses can be affected by the sending practices of other users.

Email marketer from Litmus explains that issues with email rendering, especially in HTML emails, can trigger spam filters. They recommend testing emails across different email clients and devices to ensure they display correctly and don't contain code that could be flagged as suspicious.

Email marketer from Reddit says that Hotmail's spam filters are notoriously strict, especially with new senders or those with inconsistent sending patterns. They suggest warming up your IP address and domain gradually to build a positive reputation with Hotmail.

Email marketer from Email Geeks points out that the Reply-To and From headers appear malformed, which could be contributing to the issue.

Email marketer from SendGrid recommends double-checking the DKIM configuration, including DNS records, to ensure it's set up correctly. They advise using DKIM validators to identify any errors in the signature or DNS records. A small mistake can cause DKIM to fail, leading to deliverability problems.

Email marketer from Neil Patel emphasizes the importance of proper email authentication (SPF, DKIM, DMARC) for improving deliverability. He suggests that inconsistent authentication results across different providers (Gmail vs. Hotmail) indicate a configuration issue that needs to be addressed to avoid the spam folder.

Expert from Email Geeks shares an observation that DKIM fails at Outlook for some brands, even when it's fine everywhere else, but the exact cause remains elusive.

Expert from SpamResource suggests that issues with the Reply-To address format and sender reputation can play a significant role in deliverability issues. A malformed Reply-To header or a sender with a poor reputation might be more likely to trigger spam filters in Hotmail, especially when combined with a DKIM failure.

Expert from Word to the Wise explains that the *context* and *content* of the email are critical. Given the context of the email relating to airline tickets combined with any possible problems with authentication, or other reputation issues, the filters are likely more aggressive.

Expert from Email Geeks explains that while DKIM failure might not be the only reason for spam delivery, it's crucial to fix it. They mention a rare, long-standing issue with character encoding at Outlook.com that can cause DKIM signatures to fail. Troubleshooting involves testing content for encoding problems, such as tabs or characters outside the specified character set (e.g., UTF-8 characters in an ISO-8859 message).

Expert from Email Geeks clarifies that if DKIM fails due to a "0 bit key" or DNS issue, it might be a random failure beyond control. However, if the failure is due to "signature didn't verify," it could be an encoding issue where Microsoft is altering a character.

Expert from Email Geeks explains that it is Microsoft saying to use their preferred encoding versus an equally good encoding option - ISO vs UTF kinda thing

Expert from Word to the Wise discusses the importance of proper email rendering and content. They suggest ensuring the email is properly formatted and doesn't contain elements that could be interpreted as spam signals. This could include unusual HTML structures, excessive use of images, or suspicious links.

Expert from SpamResource explains that different ISPs and email providers have varying levels of strictness when it comes to email authentication. Hotmail/Outlook.com may have a more stringent DMARC policy or a different algorithm that weighs DKIM failures more heavily than Gmail does. This could lead to different outcomes even when DKIM passes in Gmail.

Documentation from DMARC.org explains how a DMARC policy helps email receivers handle messages that fail authentication checks (SPF and DKIM). A strict DMARC policy, combined with DKIM failure, can lead Hotmail to reject or quarantine messages, while Gmail might have different handling rules based on its own algorithms.

Documentation from DKIM.org explains that a DKIM failure means the email's signature could not be verified, indicating potential tampering or issues with the signing process. While Gmail might be more lenient, Hotmail may strictly enforce DKIM, especially for transactional emails like plane tickets, which are often targeted by phishing attempts.

Documentation from RFC Editor explains that Incorrectly formatted Reply-To headers can trigger spam filters. The Reply-To field should contain valid email addresses and conform to the correct syntax as detailed in RFC specifications. Non-compliant headers can negatively impact sender reputation.

Documentation from Microsoft explains that Hotmail (Outlook) uses a proprietary spam filtering system that considers various factors, including sender reputation, content, and authentication. A DKIM failure, even if SPF passes, can negatively impact deliverability. Hotmail's filtering is more aggressive than Gmail's in some cases, leading to different outcomes.

Documentation from Google outlines email authentication best practices, which include SPF, DKIM, and DMARC. It emphasizes that while these are essential, they are not a guarantee of deliverability. Email providers consider numerous factors, and a failure in one area can impact the overall score.