Microsoft’s unreleased web-based Outlook client has been leaked for the second time, providing new clues on what Windows 10 and 11 users can expect.

Since rumours about its development first began swirling in 2020, One Outlook, known internally as Project Monarch, has been mostly kept under wraps by Microsoft – until the email client was first leaked in January 2021.

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However, the download link was only accessible to Microsoft employees and “brave dog fooders” – a tech term used to describe developers building products for their own consumption.

On 6 March, One Outlook finally became available to download for business and education accounts as “preview” or “beta”, allowing some users to get a peek at what the new email client has to offer.

Expected to ultimately replace the built-in Mail and Calendar apps on Windows 10 and Windows 11, One Outlook closely resembles Microsoft’s in-browser Outlook Web email client.

Similarly to Outlook Web, One Outlook is fully hosted online and is expected to be a simplified update to the traditional version of Outlook for Windows, which has been repeatedly criticised for numerous outages and exploitable flaws. 

Apart from a refreshed UX, including softer edges, One Outlook will be more web-centric than the original Outlook, drawing comparisons to Google’s Gmail platform. Microsoft is also rumoured to equip the new email client with Teams-like collaboration apps,

Online Microsoft news platform WindowsCentral was first to spot the latest One Outlook leak on Friday, predicting that the new email client will be officially launched in autumn 2022, eventually replacing other clients by the end of the year.

Microsoft wasn’t immediately available to comment on the leaked One Outlook. However, Scott Stiles, VP of product management for Outlook, told The Verge that more details about the update will be available “in the coming weeks”, likely coinciding with Microsoft’s annual Build developer conference on 24-26 May.

The version available for download is an early unsupported test version of Outlook for Windows and is missing some of the features and enhancements that will be available for our beta testers. We encourage our customers to wait for the beta version to be released,” added Stiles.