New Outlook for Windows 11 is noticeably slower than the Classic version when opening emails from notifications, with many users reporting long delays. While the specific claim of a consistent 10-second delay hasn't been universally verified, the performance gap is real and well-documented. Microsoft is aware of the issue but hasn't resolved it yet. This reflects a broader problem with New Outlook lagging behind Classic in responsiveness, even as Microsoft pushes users to migrate to the web-based version. The Classic version still lacks feature parity with New Outlook in areas like Mail Merge and multi-account management, leaving users stuck choosing between speed or functionality.