Microsoft issues warning about Exchange Server becoming "unstable" after October 2026 update

Microsoft has issued a warning regarding Exchange Server becoming unstable following the October 2026 update. IT admins report significant problems, including borked OWA and lengthy email queues on busy servers, after Microsoft modified a Server default. While a recommended workaround exists, administrators have expressed frustration over the time required to fix these issues. The updates have caused unexpected instability, leaving some system administrators spending entire weekends managing their servers to restore normal functionality.