Outlook365 Classic is broke

[RonPaii]

Has anyone else seen a problem with Outlook365 classic not able to connect and flashing a empty box.
I asked Google "Did Microsoft break Outlook365 classic today"

Yes, as of March 17, 2026, Microsoft reported that a previous build of Outlook 365 Classic is broken for users who have the Microsoft Teams Meeting Add-in enabled. This issue causes the application to become unusable, though updating Outlook or performing an Online Repair is recommended to fix it.
Key Details on the Outlook 365 Classic Breakage:

• Cause: A conflict between a previous Outlook build and the Teams Meeting Add-in, according to BleepingComputer.
• Impact: Users may be unable to open or use the desktop client.
• Symptoms: The bug, reported on BleepingComputer, can also lead to error codes such as 0x800CCC0F and 0x80070057 during synchronization for Gmail/Yahoo accounts.
• Mitigation: Microsoft is working with organizations to ensure users have the latest, non-impacted version of Outlook.

Other Known Issues (March 2026):

• Email Sync Errors: Additional issues with classic Outlook are causing connection problems, particularly when creating groups.
• Teams Outage: A separate outage involving Microsoft Teams has been reported to affect users in the U.S. and Europe, according to BleepingComputer.
  
  
  BleepingComputer +1

 

[isladogs]

Teams Integration Causing Office Problems

This article describes how Teams integration with Office may cause hanging instances of Office apps to remain as background processes in Task Manager. It also provides a guide to troubleshooting the problem and what changes to make if this is the cause.

www.isladogs.co.uk

 

[RonPaii]

Another symptom I saw on a computer with the problem.
In the start menu you will see Outlook and Outlook (classic).

The problem computer showed both Outlooks and the correct icons but (classic) was missing. After the online repair, (classic) was back and Outlook classic worked correctly.

 

[cheekybuddha]

Daniel Pineault has written something about this.

(I haven't read it yet! )

 

[Gasman]

Another symptom I saw on a computer with the problem.
In the start menu you will see Outlook and Outlook (classic).
View attachment 123573
The problem computer showed both Outlooks and the correct icons but (classic) was missing. After the online repair, (classic) was back and Outlook classic worked correctly.

I have the same, but my Classic works fine?
However I am on 2019.
TBH I thought I had disabled New Outlook. However I am not going to click it, just in case.

 

[RonPaii]

I have the same, but my Classic works fine?
However I am on 2019.
TBH I thought I had disabled New Outlook. However I am not going to click it, just in case.

New Outlook is never really gone.

It looks like a 365 issue where Teams is updated but Outlook was not. I always thought teams behaved differently then the rest of Office365. I think it is updated independently of Office, ignoring you update channel settings. How can It be using an older version of Outlook if all of Office is on the same update channel.

 

[isladogs]

The strange thing is that when I had the same issues in early Feb, almost nobody else reported being able to replicate them.
I decided to publish my article (see link in post #2) anyway in case the issues affected others later on.
This week is the first time I've seen any other reports.

Since applying the changes in my article, I continue to have issues with Teams itself but no longer related to using classic Outlook