Microsoft 365 Alert – Service Degradation – Exchange Online – Legacy Outlook for Mac users may be unable to connect to their Exchange Online mailboxes – RESOLVED

22/03/2024 08:54:00 AM

NHSMail Reference: INC42071614

Microsoft Reference: EX742767

Issue Status: RESOLVED

Issue Description: Users may be unable to connect to their Exchange Online mailboxes through Outlook for Mac.

Final Update: 04/04/2024 09:22:00 AM – Microsoft have confirmed that their fix has completed its deployment to the affected environment. Additionally, by verifying with affected users and monitoring the service, they’ve verified that the problem has been successfully resolved.

Scope of impact: Users on the legacy Outlook for Mac client that’s on version 15.20 and builds 7409.15 or below may be impacted.

Root cause: A recent service maintenance change introduced a code issue that inhibits communication between legacy Outlook for Mac users and the Exchange Online service, which is resulting in the impact.

Next steps: Microsoft are investigating how the recent service maintenance change introduced the code issue that inhibited communication between legacy Outlook for Mac users and the Exchange Online service to prevent this problem from happening again in the future.