Windows 10 users are experiencing a transition to the new Outlook for Windows app, which has replaced the classic Mail & Calendar app following a recent update that also addresses security vulnerabilities. The new Outlook operates as a web app, leading to performance issues and mixed reactions regarding its design. A mandatory rollout of the new Outlook began this week with the Windows 10 KB5051974 update, which will be automatically installed for users on Windows 11 version 22H2. IT administrators can manage the update and can block or uninstall the new Outlook if necessary. Windows 10 is approaching its end of support in October, with fewer updates expected moving forward, while extended support will incur additional costs.