Microsoft to replace Mail app on Windows 10 with One Outlook client

Microsoft is building a new One Outlook app to replace all the other variants for Windows 10, macOS, and the web.

One Outlook client mockup
One Outlook client mockup

One Outlook is the name of the new app that Microsoft is preparing to replace the built-in Mail and Calendar apps as well as the desktop version of Outlook and Outlook Web Access on Windows 10 and macOS for Intel and ARM hardware, and an early internal preview has leaked online.

According to some screenshots shared by @WinObs in Twitter (via The Verge) the project is currently known as “Monarch,” and it is a new version of “Outlook designed for large-screen experiences” based on the description. 

While the screenshots do not reveal any of the visual aspects of the new interface, it is expected to be based on the current web version of the Outlook.com with additional tweaks. According to a Windows Central report, the client will include native support for Windows 10, such as notifications, offline storage, share targets, and much more.

The idea with One Outlook is to build a single experience that will work across Windows 10, macOS, and the web, instead of having different clients to manage your email accounts. The new client is also expected to be available for consumers as well as for business users.

Although the company is planning to unify all its email clients into one, it will be a long time before the transition happens, since a more complete preview won’t be available until the end of 2021, and Windows 10 won’t integrate the new experience until sometime in 2022.

About the author

Mauro Huculak is a Windows How-To Expert and founder of (est. 2010). With over 21 years as a technology writer and IT Specialist, Mauro specializes in Windows, software, and cross-platform systems such as Linux, Android, and macOS.

Certifications: Microsoft Certified Solutions Associate (MCSA), Cisco Certified Network Professional (CCNP), VMware Certified Professional (VCP), and CompTIA A+ and Network+.

Mauro is a recognized Microsoft MVP and has also been a long-time contributor to Windows Central.

You can follow him on YouTube, Threads, BlueSky, X (Twitter), LinkedIn and About.me. Email him at [email protected].