Microsoft confirmed a widespread, multi-hour outage affecting Outlook and Exchange Online users on Monday, August 31, 2026, causing email delays, authentication failures, and other service disruptions.
User reports began surfacing around 11:30 AM ET, according to outage-tracking site Downdetector. By 2:00 PM ET, the site was logging more than 5,000 reports, with additional complaints appearing on social media platforms including X.
Microsoft identified the root cause as a problem with an “authentication component” affecting its Exchange Online service — the cloud-hosted platform used by businesses for email, calendar, contacts, and tasks. The company posted updates via its Microsoft 365 Status account on X, stating it had developed a remediation strategy and was testing it on a portion of its infrastructure before a broader rollout.
“We’ve confirmed that users may experience degraded functionality with various Exchange Online functionalities. We’re reviewing service telemetry and diagnostic data to isolate the source of the issue,” Microsoft wrote at 12:43 PM ET.
Microsoft later confirmed the authentication issue was affecting services beyond Exchange Online, though it did not specify which additional services were impacted.
Users affected by the outage may experience delays or failures in sending and receiving messages, mailbox search failures, authentication errors, failures with mailbox operations, and disruptions to other message delivery workflows.
The outage underscores how heavily the business world relies on email — and on Outlook and Exchange in particular — as even a partial, hours-long disruption generated thousands of reports and widespread complaints across social platforms.
Source: TechCrunch