Microsoft has resolved a bug that stopped Microsoft 365 users accessing group mailboxes and calendars in Outlook desktop clients. The affected version was released on 28 March, but the issue is being resolved via the roll-out of the latest version of Outlook, which can be installed by users via the update option.
The problem, which stemmed from a code authentication regression issue, was flagged under EX540503 in the Microsoft 365 admin center.
To solve the issue, Microsoft has recommended that affected users switch to using Outlook Web Access or revert to the previous version of Outlook Desktop. However, the company advised customers to disable updates to ensure that they do not return to the faulty version.
Microsoft also shared a temporary workaround that would enable users to access their email and group calendars while the company fixed the problem. The company noted that the problem was limited to a small number of users on versions 16.0.16222.10000 or higher, but this was likely an underestimate, given the number of user reports received.
This fix represents a welcome move from Microsoft, as it ensures that Microsoft 365 users can once again access group mailboxes and calendars on their Outlook desktop clients. It also offers users clear guidance on how to update their systems and how to avoid reverting to the problematic version.
Microsoft’s advice to disable updates is particularly helpful, as it prevents users from being inadvertently returned to the version that caused the problem in the first place.
