Some users may be unable to access shared mailboxes from Outlook on the web

Title: Some users may be unable to access shared mailboxes from Outlook on the web

User impact: Users may have been unable to access shared mailboxes from Outlook on the web.

More info: Users could access their shared mailboxes from the Outlook desktop client and Outlook mobile to avoid this issue. Additionally, if users were actively reproducing the issue on Outlook on the web, as a potential workaround we recommended users sign out of the session to ensure the existing cookies were cleared, then access Outlook on the web using the direct link for the shared mailbox, and sign in again.

Final status: The fix completed deployment and we confirmed with affected users that impact is remediated.

Scope of impact: Some users attempting to access shared mailboxes from Outlook on the web may have been impacted.

Start time: Saturday, April 13, 2024, at 5:00 AM UTC

End time: Thursday, April 18, 2024, at 3:50 PM UTC

Root cause: A recent Outlook on the web build within our service infrastructure was causing some requests to access shared mailboxes to fail unexpectedly.

Next steps:
– We’re reviewing our Outlook on the web build validation procedure to determine methods of improving the identification of similar issues in service builds that are deployed in the future.

This is the final update for the event.