Legacy Outlook for Mac users may be unable to connect to their Exchange Online mailboxes

Title: Legacy Outlook for Mac users may be unable to connect to their Exchange Online mailboxes

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

Current status: The fix deployment has completed to more than 95 percent of the affected environment. We expect the saturation of the remaining portion will take an extended amount of time to complete, and we’re continuing to monitor the progress.

Scope of impact: Users on the legacy Outlook for Mac client attempting to access their Exchange Online mailboxes may be impacted.

Start time: Friday, March 15, 2024, at 8:00 AM UTC

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 update by: Tuesday, April 2, 2024, at 1:30 AM UTC