I am writing to report an ongoing email deliver-ability issue that has been preventing users from receiving emails from apache.org since at least May 2025.
Emails sent from Apache mailing lists (e.g., @ozone.apache.org, @hadoop.apache.org, and other Apache project subdomains) are being blocked by Outlook. The root cause appears to be that these emails are not carrying DKIM signatures, which seems to have triggered Microsoft's security policies implemented around April 2025 ( https://techcommunity.microsoft.com/blog/microsoftdefenderforoffice365blog/strengthening-email-ecosystem-outlook%E2%80%99s-new-requirements-for-high%E2%80%90volume-senders/4399730 ). This issue was first reported by users on Microsoft's community forum ( https://learn.microsoft.com/en-us/answers/questions/4722114/unable-to-receive-emails-from-******@ozone-apache ) as early as June 2025. In this post, the user confirmed that he stopped receiving messages suddenly in June 2025, and standard troubleshooting (safe sender lists, checking junk folders) did not resolve the issue, indicating it is not an isolated incident but a systemic infrastructure conflict between Apache's email setup and Outlook's filtering rules. As of today (April 2026), this problem persists ( https://www.reddit.com/r/Outlook/comments/1smr1x7/anyone_else_having_issues_subscribing_to_apache/ ). This blockage is severely disrupting communication for developers and users who rely on these mailing lists for critical project updates and support.
