[German]There is an issue with Outlook Classic where the client crashes on startup due to a faulty Microsoft Teams Meeting add-in. As far as I know, Microsoft is still investigating this problem. Below, I have compiled some workarounds for those affected so that Outlook Classic can be used again.
What exactly is causing these Outlook crashes?
For example, there is a German discussion on reddit.com titled Führt das aktuelle Teams Outlook Add-In zu Abstürzen mit Office 2021? "Does the current Teams Outlook add-in cause crashes with Office 2021?" from March 16, 2026. An administrator describes there that their users are encountering the problem where Outlook (Classic) crashes upon startup with the current Teams version 26043.2016.4478.2773. If the Microsoft Teams add-in is disabled, these crashes stop.
This issue appears to affect various versions of Outlook Classic (Outlook 2016–2025 and Outlook 365). I addressed the problem a week ago in the blog post Microsoft Teams Meeting Add-in kills Microsoft Outlook Classic, and other (German and international) users have since reported the same issue
Microsoft confirmed the issue on March 17, 2026, in the bulletin EX1254044: Microsoft 365 Alert – Service Degradation – Exchange Online – Some users may be unable to use Microsoft Outlook Classic while the Microsoft Teams Meeting Add-in is enabled- ONGOING. Microsoft has found out, that an earlier Outlook build is the cause of the issue. The developers are working with their contacts to ensure that the latest Outlook version is enabled to minimize the impact, Microsoft writes
There are several workarounds
As of now, I am not aware of any official fix from Microsoft, but there are various workarounds available for those affected.
Microsoft's recommendation: Disable the add-in
n Knowledge Base article EX1254044, Microsoft recommends disabling problematic Microsoft Teams add-ins for meetings and uninstalling them if necessary. This prevents the add-in from causing issues, and Outlook Classic can be used again. However, some users have reported that the add-in was reinstalled (via an update) after one day.
Using the Old Teams Meeting Add-In
Blog reader Trog posted this comment here on the blog. He suggests extracting the file MicrosoftTeamsMeetingAddinInstaller.msi from an older Teams MSI file (e.g., using 7-Zip). Then, use Add or Remove Programs to uninstall the updated Microsoft Teams Meeting Add-in and install the older add-in instead. Here, too, it's important to ensure that Teams is not updated afterward, as the add-in will otherwise be updated to the faulty version again. The reader notes that this solution can also be easily deployed to clients via a script.
Attempt to fix the runtime libraries
In my blog post Microsoft Teams Meeting Add-in kills Microsoft Outlook Classic I outlined a workaround suggested by one of the affected users:
- In that post, the dotnet-runtime-6.0.36-win-x86.exe file was installed (since Office 2019 LTSC 32-bit is being used).
- In addition, the VC Redistributable Runtime 14.50.35719.0 was installed.
After restarting the Outlook Classic client, both the client and the Teams plugin work again. Some affected users confirm that this helped. It is reported that the VC Redistributable version 14.40 and higher likely resolves the issue.
Disable the Add-In via the Registry
If Outlook Classic freezes or crashes immediately after launching, the solutions above may not help. A reader named Stingray75 posted the following comment on the German blog. He suggests the most practical approach is to disable the Microsoft Teams Meeting add-in via a registry entry using the following PowerShell command:
Set-ItemProperty -Path "HKCU:\Software\Microsoft\Office\Outlook\Addins\TeamsAddin.FastConnect" -Name LoadBehavior -Value 2
This registry entry simply prevents Outlook Classic from loading the Microsoft Teams Meeting add-in.
Fix in MS365 app build 16.0.19127.20570?
I got a German user report, where an administrator wrote, that the issue has been gone, after they updated the Microsoft 365 apps to build 16.0.19127.20570. This is semi annual enterprise channel, and the build has been released March 9, 2026. Can this be confirmed? This doesn't fix other builds of Outlook 2019 – 2024.
