Stuck in the New Outlook? Microsoft Patches Bug Blocking Revert to Classic Version
Many Microsoft Outlook users recently encountered a frustrating issue: being locked into the new Outlook for Windows interface with no clear way to return to the familiar classic version. The toggle switch, designed to allow seamless switching between the two experiences, was failing for a significant number of people, causing disruption and workflow challenges.
Microsoft has now acknowledged the problem and deployed a fix. If you’ve been struggling to switch back to classic Outlook, an update is available to resolve the issue.
The Problem: A One-Way Street to the New Outlook
The issue stemmed from a recent update to the Microsoft 365 Current Channel. Users who had either intentionally switched to the new Outlook or were prompted to try it suddenly found they were unable to revert to the classic version.
When attempting to turn off the “New Outlook” toggle in the top-right corner, the application would either ignore the command or fail to restart in the classic interface. This left users stuck in a new environment that may not be compatible with their add-ins or preferred workflows.
The root cause was identified in Outlook Version 2405 (Build 17628.20110), where a bug prevented the application from correctly processing the user’s choice to disable the new experience. Even manually editing the Windows Registry to disable the new Outlook was reportedly ineffective for those affected.
The Solution: Update Outlook to a Patched Version
Microsoft has addressed the bug in a subsequent release. The company has confirmed that the fix is included in Version 2405 (Build 17628.20144) and later.
By installing this update, the toggle functionality is restored, once again allowing users to choose their preferred Outlook experience.
How to Fix the Issue and Revert to Classic Outlook
If you are currently unable to switch back, follow these simple steps to apply the fix and regain control.
Check for Updates: The most important step is to ensure your Outlook client is updated. To do this, open Outlook and navigate to File > Office Account > Update Options > Update Now. This will prompt the application to download and install the latest available version.
Verify Your Version: After the update is complete, check that you are running Build 17628.20144 or a newer version. You can find this information under File > Office Account in the “About Outlook” section.
Use the Toggle Switch: Once updated, simply click the “New Outlook” toggle located in the top-right corner of the application window. Outlook should now close and successfully relaunch in the classic interface you’re familiar with.
For Advanced Users and IT Admins:
If the toggle remains unresponsive or is missing after the update, a registry edit can force the change. As always, exercise caution when editing the Windows Registry.
- Open the Registry Editor (
regedit.exe). - Navigate to the path:
HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\Preferences - Find the DWORD value named
UseNewOutlook. - Set the value of
UseNewOutlookto 0. This explicitly tells the system to launch the classic version of Outlook.
The Road Ahead for Outlook
This incident highlights the ongoing transition as Microsoft pushes users toward its new, unified Outlook for Windows client. This new version is designed to replace not only the classic Outlook but also the Windows Mail and Calendar apps, creating a single, consistent experience across the platform.
While Microsoft is encouraging adoption of the new interface, the company also recognizes that many users and businesses rely on features and integrations specific to the classic version. For now, the choice to switch back remains, and this latest patch ensures that the mechanism for doing so works as intended. It is recommended that all users keep their Office applications updated to receive the latest security patches and bug fixes.
Source: https://www.bleepingcomputer.com/news/microsoft/microsoft-fixes-bug-preventing-users-from-opening-classic-outlook/
