Microsoft has fixed a known issue affecting Outlook for Microsoft 365 customers that prevented them from accessing group mailboxes and calendars using the Outlook desktop client.
The buggy version of Outlook was released to Current Channel on March 28and the fix is rolling out to all affected users with Outlook Desktop Version 2304 Build 16327.20214.
“A recent standard service update inadvertently contains an authentication code regression that prevents some users from accessing or performing various Microsoft 365 group actions in the Outlook desktop client,” the company described the issue. under EX540503 in the Microsoft 365 admin center.
“Users may not be able to view or access Microsoft 365 group calendars and email messages in the Outlook desktop client.”
To install the update that resolves this issue, affected Outlook users should go to File > Office Account > Update Options and click “Update Now”.
Users in the Microsoft 365 group affected by this known issue may experience issues when attempting to perform one or more of the following actions using the Outlook desktop client:
- Add or access group mailbox
- Add or access the group calendar
- Add, remove, or edit group members
- Mark emails or items as read
- Flag, archive, or move messages or items to other folders
Affected users are urged to re-enable updates
Microsoft too shared a temporary workaround To help affected users regain access to their group emails and calendars, a fix was ready.
The company advised them to upgrade to Outlook Web Access (OWA) or to come back to Outlook Desktop build 16130.20332, which was not affected by this issue.
As a final step in restoring Outlook to the older version, Microsoft also advised customers to disable updates to prevent the software from reverting to the buggy version.
“If you rolled back and disabled updates, remember to re-enable updates now that the fix is available”, Microsoft said Today.
Although Microsoft has stated in the admin center that the impact of this known issue is limited to a small number of users on builds 16.0.16222.10000 or higher, it was likely underestimated given the flow of user reports shared online departure earlier this month.