Project One Outlook – see how the new Outlook for Windows is different from its predecessor

[Update]: The article was last updated on May 15, 2024. Now, the new Outlook for Windows supports POP and IMAP accounts.

The new Outlook for Windows has been available in preview for some time now. Let’s see how much it differs from the classic Outlook app. Is it the right time to switch from the classic Outlook for Windows experience? What’s in store for the near future? When will the new Outlook for Windows take over the classic desktop email client? Well, let’s read and find out (or at least try).

New Outlook for Windows (One Outlook) OG

How to test the new Outlook for Windows

The Try the new Outlook toggle lets any Microsoft 365 user enable a separate (new) Outlook version. You can launch either version from the start menu. At first, both Outlook versions had the same name and the only quick way to distinguish them was to look at the icon: the new Outlook had the Pre text over it:

Outlook vs New Outlook icon PRE

But now it seems we’re nearing the time when the new Outlook comes out of the preview phase. The new Outlook no longer includes the Pre text. It now says New, both on the icon and after the Outlook’s name. The icon’s design has also changed. But looking at its size and resolution, I guess it’s still work in progress:

classic Outlook vs New Outlook icon comparison vs
Classic outlook vs new outlook icons no line vs

New Outlook for Windows release roadmap

Here are some dates related to the Outlook Monarch project that let the new Outlook come into existence.

  1. Back at Microsoft Ignite 2020, Microsoft unveiled some of the plans for making the Outlook client more uniform.
  2. Then, the first materialization of those plans was Project Monarch – a leaked build of the popular email client. It emerged in May 2022 and shown a ‘pretty much OWA’ for desktop.
  3. September 28, 2022: First release of the new Outlook for Windows for Office Insiders.
  4. April 4, 2023: The new Outlook is available in Public Preview.
  5. After the end of 2024, Mail, Calendar and People Apps on Windows 11 will become Outlook (the new Outlook). Honestly, I’m not sure if a whole lot of people will miss those, though. Now, the catch here is that Mail, Calendar and People Apps are free and the current Outlook for Windows is not. As a result, users without a paid Microsoft 365 subscription will have access to the new Outlook but with some ads displayed.
  6. There’s still no solid information about when the new Outlook will enter the General Availability phase.
  7. Based on this article from the Outlook Blog, the next step will be the “Opt out” phase. That’s when users will have to explicitly state they don’t want the new experience, instead of clicking “Try the new Outlook”. We’re supposed to get a minimum of 12 months’ notice before it happens.
  8. The final step will be a complete cutover, with no coming back to the “old Outlook”. At the moment, Microsoft states that the classic Outlook experience will be available at least until the planned support timeline, which is currently 2029.

The project One Outlook (Outlook Monarch) makes a lot of sense. Instead of providing different Outlook experience on each platform, which must take a lot of Microsoft dev teams’ resources, the app will (eventually) offer unified looks, and users will have a single place for keeping their settings.

So, the crucial question for now is when to try the new Outlook for Windows: now, soon, or wait until it’s no longer a choice? To get a clear picture, let’s have a look at the most notable differences.

How is the new Outlook for Windows different?

Basically, it’s Outlook on the web (OWA), but on desktop. The resemblance is undeniable. Still, the looks and feeling are but a small part of the changes introduced to the new Outlook. Below are some important differences between the new Outlook and the old one:

Removed features

  • COM add-ins won’t work anymore. The new Outlook for Windows supports only web-based add-ins. It’s not necessarily a bad thing, because many COM add-ins are performance-challenged. However, historically, there have been some useful add-ins that will not work in the new experience. It’s a good idea to look at what you’re using and find some replacements.
  • No more relying on Outlook profiles (Control panel > Mail > Profiles). Outlook profiles let you easily switch between different settings, especially useful for demo environments. On the other hand, without Outlook profiles, there’s no need to recreate them, for example after a migration.
  • No support for OST & PST files. For some people, it won’t make any difference. However, PST files have been used as a makeshift method (an unrecommended and not-too-reliable one, if I may add) of mailbox backup or migration. With the new Outlook, it’s no longer possible.
  • The ’old‘ Outlook allowed you to cache chosen mailbox content locally. It worked miracles when it comes to speeding up search, discovery and opening items. The new Outlook currently doesn’t have any option to cache data. However, the offline support for mail action and composing messages is a feature to be shipped in May 2024.
  • No support for Exchange on-premises (at least not yet in April 2024).
  • Initially, no support for POP & IMAP, but it’s reintroduced to New Outlook for Windows in May 2024.

Changed features

  • Outlook settings moved from File > Options to Settings. That’s inherited from Outlook on the web, as well. If you’re used to the old way of setting up your Outlook, the switch might take some getting used to. Here’s a quick look at both settings windows:
classic Outlook for Windows settings
New Outlook for Windows settings
  • Signature settings are in the cloud. While this is not a shocker after Microsoft introduced signature cloud settings, it is an important change – in the new Outlook, there’s no way back to use local email signatures. If you have some problems (like missing email signatures) after the switch, see how to solve them in this article.
  • In the new Outlook, you can Save emails to the EML format only. The old one supported saving emails to: MSG, TXT, HTML, OFT and MHT formats. The good news is, since March 2024, you should be able to open EML, OFT and MSG files in the new Outlook, so there’s some progress.
  • Outlook rules – some of the actions known from the old Outlook for Windows are no longer available, including: have server reply with a message, reply using a template, flag, clear flag, clear categories, play a (custom) sound, print, apply retention policy and display a desktop alert.

New features

  • Easy access to Microsoft To Do, Viva Engage (Yammer), Bookings, OneDrive and the rest of the Office suite (Word, Excel, OneNote, PowerPoint) from the side pane.
  • Pinning, snoozing and scheduling emails.
  • Loop components (elements that allow real-time collaboration directly in emails). Now that’s an interesting point. Loop components were one of the selling points of the new Outlook for Windows, but it turns out they were introduced in the classic Outlook for Windows as well (and work just as fine).
  • Interaction with Microsoft 365 Copilot directly from the new Outlook (added in April 2024).

Here is some more information on the new Outlook:

Things to know about the new Outlook for Windows

CodeTwo vs. the new Outlook

CodeTwo Email Signatures 365 (our email branding management tool) supports both the classic Outlook and the new Outlook. Our modern Web Add-in was featured on Microsoft Build as one of the best examples on how to use the possibilities offered by the new Outlook (and API related to it).

However, if you’re still using any of our freeware COM add-ins (some of them were popular back in the day!), it’s time to wave them goodbye. The new Outlook for Windows offers no way to support COM add-ins. And if you still use our legacy COM Add-in to insert signatures in Outlook (client-side/Outlook mode), it’s high time for an upgrade, especially since it doesn’t cost extra.

New Outlook for Windows – features roadmap

At the moment, the Try the new Outlook button encourages users to check out the new experience. This “opt-in phase” is a clear indication that we’re not dealing with the finite product. Microsoft is collecting feedback and coming up with new features even as you read this. And to see that the developers behind the new Outlook are quite busy, you can take a look at the roadmap, filtering results by:

The list is extensive. The most recent ones that caught my attention are:

  • Newsletters – that’s a brand-new thing. The new Outlook will enable users to create and distribute internal email newsletters. It is said to include analytics to track internal campaigns’ performance.
  • Conditional formatting – the feature introduced with the classic Microsoft Outlook 2010.
  • Drag and drop to download attachments and emails. Again – a heavily used feature known from the classic Outlook.
  • ICS support –the lack of this feature baffled users around the globe. Support for ICS files simplifies event and calendar management and was introduced in the new Outlook in September 2023.

Now, for me, it’s reassuring to know that Microsoft is finding a way to reintroduce well-known and extensively used features that initially were missing from the new Outlook for Windows preview. When looking at the snarkiest comments about “One Outlook”, the “missing features” section is the recurrent theme.

And now for the section that made (at least for a while) the new Outlook for Windows unusable to me. I ran across a problem that didn’t let me sign in to the new Outlook for Windows and I’ll show you how I managed to fix it.

Troubleshooting – Something went wrong when launching the new Outlook for Windows

Problem description

When you launch the new Outlook for Windows, you see a prompt to sign in. The sign-in attempt ends with the error message:

Something went wrong

We ran into an error – Error: GlobalSettingsAccountLogonFailed

or similar.

Outlook: Something went wrong. We ran into an error - Error: GlobalSettingsAccountLogonFailed


Go to your local AppData folder (C:\Users\YourUserName\AppData\Local\Microsoft) and delete the Olk folder. If it doesn’t help, delete the OneAuth folder, too. Try running the new Outlook for Windows again.

New Outlook for Windows troubleshooting - delete Olk folder


It took me much more time than I’d like to admit to fix this problem.

When first trying to launch the new Outlook for Windows in a lab environment, Outlook wanted me to sign in with another user’s credentials. The problem was that the user’s account was long gone – neither the user nor their Microsoft 365 tenant existed any more. It didn’t prevent the user’s profile from being cached, though.

Unlike the standard sign-in prompt, this one didn’t let me sign in as another user. First attempt to close the sign-in window caused it to appear once again. The second one returned the LogonFailed error.

What I tried:

  • Repairing and reinstalling the Office suite (Microsoft 365 Apps for Business).
  • Clearing all the info in the Windows Credential Manager.
  • Deleting & recreating all Outlook profiles.

None of these actions made any impact. The search for the cached profile location was the final step before dropping the ’format c‘ bomb on my lab environment.

Tools for Microsoft 365

5 thoughts on “Project One Outlook – see how the new Outlook for Windows is different from its predecessor

  1. If the don’t, its a big fail. Also it should be able to open .pst files. We are storing 20 years+ of business emails in those archives.

  2. I would like to see a split dark mode next, so you don’t have to click the sun icon in every email. Let people select a theme that has a light mode for the reading pane, but the rest of the theme views in dark mode.

  3. I’m very happy that .oft files now open in the new outlook! You can’t create them from new outlook though, you have to create them in the old outlook. Hopefully in 2024 they add “save as .oft” into the new outlook.

  4. Hi
    do you know and can help : how to set new ms outlook (outlook one? – native windows 11 mail client) to work with MS Exchange serv on prem? there is no option in first starting wizard.. (I mean there is visible option Exchange, but there is no field to enter mail name or adress of server :( )
    Best Regards

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