Microsoft's 'One Outlook' email client may arrive in preview this spring

Outlook Web App
Outlook Web App (Image credit: Windows Central)

What you need to know

  • One Outlook (Project Monarch) is almost ready for preview.
  • It could arrive as soon as this March.
  • This is Microsoft's (eventual) replacement for Mail & Calendar on Windows 11.

Last year, Windows Central reported that Microsoft was working on a new Outlook client, codenamed "Monarch" and based on Microsoft's Outlook Web experience. Originally, Microsoft expected to begin shipping the app in preview in the summer of 2021, and replace the Mail & Calendar apps on Windows 11 later this year. For whatever reason, that initial preview never arrived.

Now, a report from ZDNet's Mary-Jo Foley has shed some light on the whereabouts of Project Monarch, stating that the app is still in development and may arrive in preview as soon as this spring. Microsoft does still intend to replace the Mail & Calendar apps, though that may not happen this year. Instead, Microsoft will place the new Outlook client alongside the Mail & Calendar apps while users get used to the new experience.

Microsoft has been testing Monarch/One Outlook for several months internally with increasingly large rings of employees. My sources say the company is planning to make an official announcement about One Outlook this spring. Microsoft could be ready to get a test version of the new Outlook to Windows Insiders in the Dev and Beta channels by late March or early April 2022, my contacts say. By late July or August this year, Microsoft is hoping to be able to get it to Insiders in the Slow Channel, though this target date could slip until the fall, my contacts said.

Microsoft has been hard at work on its new One Outlook client for well over a year at this point. It's Microsoft's goal to consolidate and unify the Outlook app experiences on desktop with a single client that's powered by the web. Microsoft hopes that this new client will eventually replace Mail & Calendar as well as Outlook Win32, though that plan is much further out.

For now, we're getting close to the first preview release of One Outlook, which Foley states will roll out first to Insiders in the Dev and Beta Channels in late March or early April. It'll then make its way to the Insider Slow Channel sometime in the summer.

Zac Bowden
Senior Editor

Zac Bowden is a Senior Editor at Windows Central. Bringing you exclusive coverage into the world of Windows 10 on PCs, tablets, phones, and more. Also an avid collector of rare Microsoft prototype devices! Keep in touch on Twitter: @zacbowden.

  • OT but do you guys know anything about Microsoft Loop standalone app launch? And will it be targeting individuals too or just companies?
  • I want to know this too. They're awfully being silent about it and their announcement was so vague.
  • This is so long coming. Outlook on web is an amazing client full of AI smartness, but especially on business accounts can't integrate multiple inboxes and doesn't work offline. Main outlook app has so many features, mostly hidden, but works offline and integrates multiple accounts. There is a v clear need to merge all this. Hope they do it well and then there is only one Outlook.
  • I would prefer Outlook in 365 to the version. The latter annoys the hell out of me by not having an option to turn off grouping email by today, yesterday, etc.
  • I hope that this PWA One Outlook app will have rich notification and support at least notification badges, Jumplist and has integration with Windows Share. It would be a shame to not have those, since sadly they tend to forget or abandon some features when they do app platform switch. Of complete offline support that can store emails locally and can be searched using Windows Search without having to open the app first. Also native Widget support please.
  • Heck no! We need native apps. Not a PWA wrapper for the website. If they do that, we'll lose multiple features in the process and millions of people will need to relearn where to find features they use on a daily basis.
  • What a disappointment that it isn't going to be any different than I hope that isn't true.
  • The picture in the post is just a screenshot of the PWA. It's not the actual One Outlook app. They won't be able to replace the existing Win32 app until feature pairity and true offline support, so I'm guessing it'll be like the Teams app where it's a mix of web and native app, so it feels and works like a traditional app.
  • Will this new Outlook work offline? Can it open in under 100 ms? I love Mail on Windows 10 and 11 because it opens so fast and can work offline.
  • What is the point of trying to make a website work offline when most of its features depend on a connection?
  • Another slow and heavy web app? no thanks
  • Will the mobile clients stay different?
  • If they do then how is it "One Outlook"? If they aren't different, then I expect a lot of functionality to be lost. Have to work to the lowest common denominator.
  • Windows 10 should get it too, right? Hope that this one will be more reliable :/ I gave a try to Mailbird finally
  • And again, Microsoft is on a rampage in order to break software that was working just fine beforehand in an attempt to downgrade the experience of desktop users to that of the website...just because it's easier to maintain. Why give any choice to the users?