Microsoft Exchange Online Outage Causes Email Failures and Auth Issues

Microsoft Exchange Online Outage Causes Email Failures and Auth Issues 🚨

Microsoft is investigating a widespread service issue causing authentication issues, connection problems, email delays, and failures for Microsoft 365 customers. It first acknowledged this incident (tracked under EX1464935 in the admin center) at 5:30 PM UTC, when it began investigating a stream of reports from users on social media regarding multiple issues affecting Exchange Online.

According to outage tracking service Downdetector, tens of thousands of Outlook and Microsoft 365 users are affected and experiencing issues receiving emails via Outlook and accessing Microsoft cloud services.

Impacted Services

While Exchange Online is the most impacted service, Microsoft revealed in a new incident report (MO1465074) that this outage also affects multiple other Microsoft 365 services, including:

• OneDrive for Business
• SharePoint Online
• Microsoft Teams
• Microsoft Purview
• Microsoft Defender XDR

The list of Exchange Online symptoms includes:

• Delays or failures when sending or receiving email messages
• Delays, failures, or incomplete results when searching for content within Exchange Online mailboxes
• Authentication-related errors when accessing Exchange Online services
• Difficulties accessing or performing actions within Exchange administration experiences
• Intermittent failures affecting mailbox operations and message delivery workflows

Although the company has yet to reveal which regions are impacted, it has classified this outage as an incident, which is typically used to describe critical service issues with noticeable user impact.

Latest Updates

On August 31, Microsoft updated its assessment, stating, “We’ve identified issues related to a core authentication configuration used by multiple internal services within the Exchange Online infrastructure.” Earlier, the company noted, “We’ve isolated a common failure pattern across affected Exchange Online requests that is associated with authentication and protocol connectivity.” Microsoft also stated, “We’re performing a manual test on the individual server level to reset configurations to validate if this resolves the issue.” The company is analyzing service telemetry to identify the underlying source of impact and validate potential remediation options while continuing to assess the scope of impact and monitor for additional affected scenarios.

Microsoft has addressed multiple Exchange Online outages in recent months, most recently in June, when it mitigated a widespread service issue affecting the mail flow pipeline for customers across North America, Asia-Pacific (APAC), and Europe. In April, it also resolved Exchange Online mailbox access issues that had intermittently impacted Outlook mobile and macOS users for weeks, and an Exchange Online outage that prevented users from accessing their mailboxes via Outlook on the web, Outlook desktop, Exchange ActiveSync, and other Exchange Online connection protocols.

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