Enlarge / The new Outlook client for Windows is creeping nearer to release, though it still doesn't support some important features. (credit: Microsoft)

Earlier this year, Microsoft released a preview of a totally redesigned Outlook for Windows client. It was a step closer to something Microsoft has been working toward for a while—a unified Outlook client across all of its platforms, based on the design of the web version. Today, Microsoft is taking another step toward that goal, with an updated preview for the new Outlook client that will be available to all Office Insiders in the Beta and Current channels.

Outlook for Windows users signed up for the Office Insider program will be able to try the new app by hitting a "try the new Outlook" toggle in the upper-right corner of the app window; hit the toggle again to return to the old Outlook app. Microsoft says toggling between the two will result in "no data or email loss."

The Outlook app will also eventually be replacing the free built-in Mail and Calendar apps preinstalled in Windows. Microsoft will make a similar toggle available to Windows Insiders "in the coming weeks."

Enlarge / Using Teams in a browser is actually safer than using Microsoft's desktop apps, which are wrapped around a browser. It's a lot to work through. (credit: Jernej Furman / Flickr )

Microsoft's Teams client stores users' authentication tokens in an unprotected text format, potentially allowing attackers with local access to post messages and move laterally through an organization, even with two-factor authentication enabled, according to a cybersecurity company.

Vectra recommends avoiding Microsoft's desktop client, built with the Electron framework for creating apps from browser technologies, until Microsoft has patched the flaw. Using the web-based Teams client inside a browser like Microsoft Edge is, somewhat paradoxically, more secure, Vectra claims. The reported issue affects Windows, Mac, and Linux users.

Microsoft, for its part, believes Vectra's exploit "does not meet our bar for immediate servicing," since it would require other vulnerabilities to get inside the network in the first place. A spokesperson told Dark Reading that the company will "consider addressing (the issue) in a future product release."

Enlarge / The new Outlook client for Windows will unify the web and offline clients—when it's done, anyway. (credit: Microsoft)

For years now, Microsoft has been planning behind the scenes to unify its disparate Outlook clients across the web, Windows, and macOS. Today, that goal moved one step closer to completion with the introduction of a new Outlook client for Windows users that closely mirrors the interface and functionality of the Outlook web client.

The new app is available to Office Insiders in the Beta channel who have work or school Microsoft 365 accounts. Regular Microsoft accounts aren't currently supported. This appears to be the same version of the Outlook client that leaked to the public a couple of weeks ago .

A unified Outlook client, also known as "One Outlook" or "Project Monarch," will be an especially welcome change for Mac users. The Mac version of Outlook has always looked different from and been less fully featured than the Windows client, though the current situation is much better than the bad old days of Microsoft Entourage .