Microsoft 365 Alert – Service Degradation – Exchange Online – Some users may be unable to view or access group calendars and email messages in the Outlook desktop client – RESOLVED

12/04/2023 14:20:00 PM (GMT)

NHSmail Reference : INC35283692

Microsoft Reference : EX540503

Issue Status : RESOLVED

Issue Description : Some users may be unable to view or access group calendars and email messages in the Outlook desktop client.

More Information : Affected users are part of a Microsoft 365 group; however, these users may also be unable to perform one or more of the following actions in the Outlook desktop client:

– Add or access the group mailbox
– Add or access the group calendar
– Add, remove, or edit group members
– Mark emails or items as read
– Flag, archive, or move mail or items to other folders

Final Update : 03/05/2023 09:21:00 AM – Microsoft have confirmed that the fix has reached all affected environments. Users will be prompted by the client to update their build to 16.0.16327.20214, which will resolve the problem.

Scope of impact : Impact was limited to users of Outlook desktop client versions 16.0.16222.10000 or higher that attempted to access or perform various Microsoft 365 group related actions.

Root cause : A recent service update was incorrectly triggering an indexer to delete specific values within the Outlook desktop client for some users, resulting in impact.

Next steps : Microsoft are reviewing the deployment procedures to better understand how this issue wasn’t identified during testing and validation, which will help prevent similar issues in the future.