Delegate users may have been unable to send emails to contact lists for shared mailboxes in Outlook on the web

Title: Delegate users may have been unable to send emails to contact lists for shared mailboxes in Outlook on the web

User impact: Delegate users may have been unable to send emails to contact lists for shared mailboxes in Outlook on the web.

More info: Whilst we were focused on remediation, users may have been able to use Outlook desktop and mobile app to bypass the impact. Furthermore, affected users may have been able to browse to the contact list in the ‘PeopleHub’ and click the ‘Send Email’ button on the desired contact list.

Final status: We’ve successfully deployed the fix to repair the regression and confirmed that impact has been remediated.

Scope of impact: Impact was specific to any delegate user, served through the affected infrastructure, attempting to send emails to contact lists for shared mailboxes in Outlook on the web.

Start time: Wednesday, July 12, 2023, at 12:00 AM UTC

End time: Friday, September 22, 2023, at 12:00 AM UTC

Root cause: A recent service update, intended to update the APIs used for contact searching in Outlook on the web, inadvertently contained a code regression.

Next steps:
– We’re reviewing our update procedures to better identify similar issues during our development and testing cycles.

This is the final update for the event.