Gmail has made significant improvements to its automated filtering in an effort to reduce spam, resulting in a decrease in transactional messages going to the spam folder. However, this change appears to have caused issues with delayed or missing messages for some senders, particularly those using Postmark's transactional-only message policy. The issue seems to be affecting specific senders indiscriminately, regardless of their sending volume or reputation, and is likely due to Gmail's increased focus on blocking spoofing and phishing attacks. To mitigate the issue, customers can wait for Gmail to update its systems and submit examples of affected messages to improve the filters faster. In some cases, changing authentication subdomains has helped Postmark customers get back into the inbox, but this may not be a viable solution for everyone. The impact of this change is currently limited to specific senders, and monitoring engagement rates can help identify if own messages are affected.