Microsoft is testing a new Outlook application to replace the built-in mail and calendar applications in Windows 10. Codename Monarch and “One Outlook”, the application “New version of Outlook designed for better experience“, According to the leak.

Although a leaked application without an internal Microsoft account is not working, one will replace the desktop versions of Outlook (win32 and UWP), Outlook Web Access (OWA), and macOS clients. Microsoft also provides a full version of the new Outlook online.

Microsoft is essentially developing a desktop client based on the online version of Outlook. The leaked app is clearly in its infancy and Microsoft has also warned its employees that it is for “brave dogfooders” and is not yet running without internet access. For information, “dogfood” is a term used by Microsoft and other companies to test and use early versions of their applications.

The initial version may have leaked, but the final replacement for the Windows 10 Mail app may be released in 2022. Windows Central states that the Outlook client will likely go by the end of 2021 with the goal of undergoing a comprehensive test. Mail and calendar applications in Windows 10 are to be done in 2022.