[German]Microsoft actually wanted to start migrating business users to the new Outlook app at the beginning of 2025. Redmond has now announced that this rollout will not take place until April 2026 for business users with an Microsoft 365 Enterprise license.
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Original plans for the new Outlook app
Microsoft only wants to support classic Outlook until 2029, but in the meantime migrate users to the new Outlook app, which has been under development since 2023. It was announced some time ago that users of a Microsoft 365 Business Standard and Premium license would switch to the new Outlook for Windows from 6 January 2025 in the blog post Migration from Outlook Classic to New Outlook starts for business customers at the beginning of 2025.
Note: This migration date for Microsoft 365 Business Standard and Premium licenses is still valid.
Mandatory migration for MS 365 Enterprise in April 2026
In view of the many shortcomings of the new Outlook app, this approach seemed quite ambitious to me. n the comments section of the blog, a German reader wrote on December 9, 2024 that Microsoft had postponed the migration to 2026 as of December 6, 2024 under the message ID MC949965.
It stated that users of Microsoft 365 for Enterprise will not be switched from the classic Outlook to the new Outlook for Windows until April 2026. However, there is the option to switch back. In Microsoft-speak, this change is aimed at improving the user experience with modern functions. Organizations would be notified to prepare.
I now have access to the full text in the message center via the patchmanagement.org mailing list (see end of article). I assume that Microsoft has received a lot of pressure from major customers to postpone the rollout of the unfinished new Outlook app.
Microsoft hints in the announcement that it now wants to give customers more than 12 months to prepare for the switch. From April 2026, users with Microsoft 365 for Enterprise licenses will be migrated from classic Outlook for Windows to new Outlook for Windows.
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Users will still have the option of returning to and using classic Outlook. However, in a game of cat and mouse, Microsoft states that users will be switched to the new Outlook once in April 2026. If they switch back to classic Outlook, they can be switched again in the future.
So in the sense of: Announce bad news positively, it then also states that "the automatic rollout requires no administrative action, but allows opt-out options." Microsoft describes in the support article Control the installation and use of new Outlook how administrators can prevent this changeover. I also described possible "administrative measures" in the form of scripts in the article Prevent migration from Classic Outlook to New Outlook.
Final thoughts
Written in a positive manner, Microsoft is initiating the migration to the new Outlook for certain customers (with Microsoft 365 Business Standard and Premium licenses) in just over 4 weeks. But there is "a staged rollout", because (big) customers with Microsoft 365 Enterprise license get another 12 months of rest, during which Microsoft can knock the biggest blunders out of the new Outlook app and maybe implement a few missing features.
You could also describe it as "what a mess", which imho threatens administrators. Depending on which license is currently being used, the migration will come in four weeks or a year later. The only possible remedy: Actively block the migration via the registry entries mentioned above – and read Timo's German comments.
Here is the full text from the Message Center.
Toggle to new Outlook – MC949965
We're making some changes to the migration from classic Outlook to new Outlook for Windows.
We aim to give more than 12 months of notice to help our customers prepare. Starting April 2026, users with Microsoft 365 for Enterprise licenses will be toggled from classic Outlook for Windows to new Outlook for Windows. Users will be toggled into new Outlook once with this roll-out, with potential to be toggled again in the future. Users will maintain the ability to go back to and use classic Outlook.
Our goal with this change is to give users an opportunity to try new Outlook as millions of users already have. New Outlook gives users the most modern experience with Copilot features, theming, and a wave of valuable time-saving features like Pinning and Snoozing mails. Users are also welcome to give us feedback on new Outlook using Feedback in the Help ribbon, so we can tailor the best email and calendar experience.
When this will happen:
General Availability (Worldwide): We will begin rolling out April 2026.
How this will affect your organization:
You are receiving this message because our reporting indicates one or more users in your organization are using Microsoft 365 Enterprise licenses.
Users will have notice in the application prior to being toggled and will have the option to opt out of the experience in Outlook Options > General. Users who are toggled into new Outlook can toggle back to classic Outlook if they choose to.
Users will not be toggled if one or more of the following is true:
- You have opted your users out of being automatically toggled per Admin-Controlled Migration to New Outlook
- New Outlook toggle is hidden via policy
- Perpetual license is in use
- On premise account
User-facing article: Switch to new Outlook for Windows – Microsoft Support. We will continue to update this article as we get closer to April 2026.
What you need to do to prepare:
This rollout will happen automatically with no admin action required starting April 2026. You may want to notify your users about this change and update any relevant documentation as appropriate. When this change takes effect, if you choose to exclude users from the experience, you can use the following Admin policy to manage new Outlook migration: Admin-Controlled Migration to New Outlook
Later, this policy will also be available via Group Policy Objects (GPO), Cloud Policy, and Intune.
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