Microsoft has acknowledged that Classic Outlook can mysteriously transform into a system resource hog, causing CPU usage spikes between 30-50% and significantly increasing power consumption on both Windows 10 and 11 systems.
Users first reported the issue in November 2024, but Microsoft only confirmed the problem this week, offering little resolution beyond stating that “the Outlook Team is investigating this issue.” The company’s sole workaround involves forcing a switch to the Semi-Annual Channel update through registry edits — an approach many enterprise environments will likely avoid. Microsoft hasn’t announced a definitive end date for Classic Outlook, but the company continues pushing users toward its New Outlook client despite its incomplete feature set.
