‘Postmaster Delivery Failure Notification’: How a Simple Bounce Email Can Expose Your Security Controls
Most organizations focus on stopping phishing emails from reaching users. However, many do not realize that their email system may reveal useful information to an attacker when a suspicious email is blocked. In Microsoft 365, a failed email usually generates a message such as “Postmaster Delivery Failure Notification” or “Delivery Status Notification (Failure).” These messages […]

