Users may be unable to access the Exchange Online service through multiple connection methods

Title: Users may be unable to access the Exchange Online service through multiple connection methods

User impact: Users may have been unable to access the Exchange Online service through multiple connection methods.

More info: The affected connection methods included:
– Outlook for the web
– Representational State Transfer (REST) API
– Calendar access through the Microsoft Teams apps
– Search through Microsoft Teams desktop client and web app

Some users may have received a message on the Outlook desktop client stating “Outlook is trying to retrieve data from the Microsoft Exchange Server outlook.office365.com”

Users may also have been unable to back up their mailboxes through third-party apps when leveraging Exchange Web Services (EWS).

Final status: We’ve finished applying our configuration changes to expedite resolution and confirmed via service health telemetry information that all impacted scenarios have been remediated successfully.

Scope of impact: This issue may have potentially impacted any user attempting to access the Exchange Online service through Outlook for the web, methods utilizing the REST API, or their calendar through the Microsoft Teams apps.

Start time: Tuesday, September 12, 2023, at 4:00 PM UTC

End time: Friday, September 15, 2023, at 9:40 PM UTC

Root cause: A recent change intended to provide an updated method for our search service to perform searches introduced the latency responsible for impact.

Next steps:
– We’re reviewing our change testing and validation procedures to identify how impact was missed and better prevent similar future occurrences.

This is the final update for the event.