[German]For weeks, Microsoft Outlook 365 users have been plagued by a program that crashes on startup when connecting to Exchange Online. Microsoft now plans to roll out a fix to resolve the issue.
Review of the problem
This is a problem that I addressed in early October 2025 in the blog post Microsoft confirms Outlook 365 bug that can only be fixed by support. There is a problem in Outlook 365 that causes the classic Outlook email client to crash when it starts up. Affected users receive the following error message when starting Outlook Classic on Windows:
"Cannot start Microsoft Outlook. Cannot open the Outlook window. The set of folders cannot be opened. The attempt to log on to Microsoft Exchange has failed."
This only seems to occur in certain scenarios when the client accesses Exchange Online. If I understand correctly, an authentication limit occurs that prevents Outlook 365 access and causes the client to crash.
Fix instead of support case
According to Microsoft, there are several possible reasons for this error message. Microsoft stated in its support article that it is investigating this issue. Microsoft recommends that users affected by this bug use Outlook Web Access (OWA) or the new Outlook for Windows. The problem should not occur in either of these solutions.
Affected users who rely on the Outlook Classic client had no choice but to open a support case with Exchange Online Support via their IT department using the Microsoft 365 admin portal. Exchange Online Support must request a service change to resolve the issue.
Apparently, a solution to this problem has now been found in Redmond. Microsoft has added a short note to the support article on October 20, 2025. The status of the bug has been set to "Fixed," and Microsoft writes that the service team has made changes to resolve the issue. They are currently monitoring the situation to ensure that the problem has been resolved. Were any of our readers affected, and can you confirm that the bug has been fixed?
