User impact
Users may be unable to access shared mailboxes from Outlook on the web.
Description
Users can access their shared mailboxes from the Outlook desktop client and Outlook mobile to avoid this issue. Additionally, if users are actively reproducing the issue on Outlook on the web, as a potential workaround we recommend users sign out of the session to ensure the existing cookies are cleared, then access Outlook on the web using the direct link for the shared mailbox, and sign in again.
Scope of impact
Some users attempting to access shared mailboxes from Outlook on the web may be impacted.
Root cause
A recent Outlook on the web build within our service infrastructure is causing some requests to access shared mailboxes to fail unexpectedly.