Microsoft initially said users in India are the primary group impacted. However, the company later confirmed on the Microsoft 365 Status Twitter account that the issue is affecting users worldwide.
Downloaddetector currently indicates the worst impacted regions include the UK, France, Germany, Netherlands, Belgium, Norway, Sweden, and India. There are also multiple user reports on Twitter from users in Europe who've been unable to access Outlook as the workday begins.
This new incident follows a six-hour Office 365 failure earlier this week due to an authentication error that prevented users from signing into Office.com, Outlook.com, Teams, Power Platform, and Dynamics365. Microsoft was forced to roll back a recent change that impacted authentication operations for numerous Microsoft and Azure services.
Microsoft's Office Service health dashboard also confirms that users of Outlook.com "may be unable to access their email".
"We're collecting additional data from the affected infrastructure to aid in our investigation to determine the cause of impact," Microsoft said.
Similar to the incident earlier this week, Microsoft said it is investigating recent updates it has made to its service to identify the potential source of the problem. However, there's no indication of when the issue will be resolved.
"We're reviewing recent changes to our service to further determine the cause of impact. Users may experience problems with various Exchange Online protocols, including Outlook desktop, mobile devices as well as those dependent on REST functionality," Microsoft said.
The company followed up that message to say it has diagnosed that a recent configuration update to components that route user requests is the cause of the outage.
"We've reverted the update and are monitoring the service for recovery. We apologize for the inconvenience."