This rule is designed to detect phishing emails that impersonate email system notifications regarding delivery failures or other email system issues. The content of these phishing emails typically suggests that incoming messages could not be delivered and often directs users to malicious links claiming to resolve the issue, thereby harvesting user credentials. The detection mechanism evaluates various aspects of the email including the body text, subject line, and hyperlinks present. Specifically, it looks for signs of impersonation by analyzing the intent of the email content using Natural Language Understanding (NLU), checking for specific phrases commonly associated with email issues, and identifying potentially malicious links with suspicious display text or domain names. Furthermore, the rule incorporates checks against trusted domains and validates email headers to ensure proper DMARC authentication, thus filtering out legitimate messages from known major email service providers. This multifaceted approach helps to minimize false positives and accurately identify genuine phishing attempts.