Using classic Outlook for Windows in business environments
Yes, there is currently a widespread Microsoft 365 service disruption that is affecting Outlook and several other Microsoft services.
Outlook relies on Exchange Online for its email services, and Microsoft has confirmed that users may be unable to access their mailboxes through Outlook on the web, desktop, or mobile devices. Email delivery may also be delayed.
According to Microsoft's latest update, the company is seeing positive results from restarting the affected infrastructure and is monitoring server stability while continuing its recovery efforts. However, full service restoration has not yet been confirmed.
You can check the Microsoft 365 Service Status for the latest updates.
I recommend checking the service status page periodically and waiting for Microsoft to complete its recovery efforts before attempting major troubleshooting steps.