Microsoft is investigating a known issue that causes the classic Outlook email client to crash upon launch, which can only be resolved via Exchange Online support.
According to a recently published support document, this impacts Microsoft 365 customers who use classic Outlook on Windows systems.
While the company didn't specify the root cause of this ongoing issue, it advised affected customers to open a support case from the Microsoft 365 Admin portal, which will prompt the Exchange Online support team to request a service change to mitigate it.
"This error message can occur for different reasons. Not every instance of this error is the same issue but recent support cases around this have been for user mailboxes," the company said.
"Currently, the only way to address this issue is to open a support case from the Microsoft 365 Admin portal. Exchange Online support will need to request a change from the service to mitigate."
On affected systems, users are seeing an error message warning that Outlook cannot start, and an attempt to log into the Exchange account has failed.
While the company is still investigating and working on a fix, it prompted those seeing this error to confirm if they're affected by capturing a Fiddler trace and searching for an "LID: 49586 - Authentication concurrency limit is reached." error.
Microsoft also said that affected customers could use the new Outlook for Windows or Outlook Web Access (OWA) as a temporary workaround to access their mailboxes.
Another support document addressing "Cannot start Microsoft Outlook. Cannot open the Outlook Window" errors prompts users to go through the following troubleshooting steps to resolve Outlook startup issues:
- Start Outlook in safe mode and disable add-ins
- Create a new Outlook profile
- Repair your Outlook data files
- Run the /resetnavpane command
Since the start of the year, Redmond has also fixed a known issue causing CPU spikes when typing messages in classic Outlook and a bug that broke email and calendar drag-and-drop functionality in classic Outlook after installing Windows 24H2 updates.
More recently, it addressed a bug that triggered classic Outlook crashes when opening emails or starting new messages and shared a temporary fix for a known issue that caused Outlook errors when opening encrypted emails sent from other organizations.
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Comments
NMI - 2 days ago
WTF is a Fiddler trace?
JustAnotherEndUser - 23 hours ago
"Accident" or "encouragement" to move to the subpar "new" Outlook web app.
AllOfUsAreHere - 16 hours ago
Windows is just a terrible product. Oh wait, It's been 10 minutes time for another reboot
morbius007 - 15 hours ago
Microsoft is now so desperate to force people into making Microsoft accounts and to use the awful AI slop they are pushing that they are integrating it into everything and removing the option to bypass it. First they tried to sell it, then they tried to convince everybody it was this amazing feature set, then they realized nobody wanted it but they are already committed to spending billions of dollars on this garbage and they dont know how to stop the runaway train.
According to everything I have researched only 5% of AI projects are bearing any fruit in terms of profitability, and even in those cases the use case is very much marginal for most people, AI general intelligence is years away like it always is. The existing AI is nothing but an enormous decision tree that they keep adding branches to. Eventually the tree will stop growing "we may already be there" and the next stage of development will be started, but that new trunk of the tree will take a decade or more to get dialed in. And once this new tech is implemented and it indeed can replace low level employees, we are in for a bumpy ride with companies, "MS" and other IT folks clamoring for more and more of our personal information to consume.
morbius007 - 15 hours ago
The new motto of Microsoft when it comes to their own customers. Our users have "Too many secrets" we need to know everything to "help" them into the future. Microsoft and other big tech companies will do everything and anything to curb privacy laws going forward, they are dead in the water if anything of that kind of thing gets any momentum. We have new data breaches "DAILY" and nobody is being held responsible, just more calls for more data and more centralization and more digital surveillance to train the next AI model, it's time to cut off the diseased arm of this user information fed system and get our own representatives to put in place laws which ban companies from both collecting and selling our personal information.