Microsoft completed the mitigation actions and confirmed that the issue was resolved after an extended monitoring period.

Microsoft reported that most impacts had been remediated, with service availability at 99.9%. Microsoft continues to monitor the environment and perform targeted restarts on back-end mailbox components that show the residual effect to ensure recovery for all users.

Outlook.com functionality, such as Calendar APIs consumed by other services such as Microsoft Teams is also affected.

Microsoft is trying to resolve the issue.