The Win32 classic version of Outlook is a desktop application that Microsoft has been working on consolidating with the new Outlook for Windows since at least 2021.

Microsoft could take the wraps off its 'Project Monarch'/One Outlook project this spring, after months of internal testing.

Microsoft's new Outlook mail client, codenamed 'Project Monarch,' seems ready to roll out in preview any time now.

Right now, Microsoft has a number of different Outlook clients for desktop, including Outlook Web, Outlook (Win32) for Windows, Outlook for Mac, and Mail & Calendar on Windows 10.