Microsoft 365 - some issues with mailbox and calendar functionality

Microsoft have now resolved their incident reference MO941162

"After a period of extended monitoring, we’ve confirmed through customer reports and service health telemetry that the issue is resolved."

Thanks for your patience while this was progressed.

Microsoft have made a number of updates to their Service Status post overnight.

They have restored all services with the exception of Outlook on the web - where they are continuing to investigate mail queue delays in a small number of environments. They've entered an 'extended monitoring phase' until that is completed.

We'll update/resolve this post once Microsoft move their incident to resolution.

From the updates from Microsoft at 13:30, 13:58 and 14:27 - a summary:

Microsoft have identified the root cause and have developed a fix - which, after testing - they've started to deploy to affected environments.

The fix has now been deployed to 60% of the affected environments

We will update this Service Status post as/when Microsoft move their issue towards resolution.

Microsoft have posted an update to their issue reference MO941162:

"We’ve identified a recent change which we believe has resulted in impact.

We’ve begun to revert the change and are investigating what additional actions are required to mitigate the issue."

Their next update is scheduled for 14:00 GMT.

Microsoft have acknowledged an issue this morning where "users may be unable to access their mailboxes or their calendar functionality in Microsoft Teams"

"Users may be unable to access Exchange Online using the following impacted connection methods

Outlook web

Outlook desktop

...

Users may also be unable to access or modify their calendar in Microsoft Teams. This would include loading calendar, viewing meetings, creating/updating meetings and joining meetings."

The Microsoft incident reference is MO941162

We will update this post accordingly as Microsoft progress their investigation. Their next planned update is at 12:00 GMT.

Apologies for any inconvenience.