Users of **Microsoft Exchange Online** are currently facing a widespread service outage, leading to authentication problems, email delays, and failures across the platform. **Microsoft** acknowledged the incident, designated **EX1464935** in the admin center, at 5:30 PM UTC following a surge of user reports. Outage tracking service **Downdetector** indicates that tens of thousands of **Exchange Online** users are affected, struggling to receive emails via **Outlook** and access the **Exchange Online** platform itself.  ### Reported Symptoms **Microsoft** has detailed a list of symptoms users may encounter: * 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. While the specific geographical regions impacted have not been disclosed, **Microsoft** has classified this as an incident, a classification typically reserved for critical service issues with significant user impact. ### Current Investigation and Past Incidents **Microsoft** stated in its latest admin center update: "We've isolated a common failure pattern across affected **Exchange Online** requests that is associated with authentication and protocol connectivity. We're analyzing service telemetry to identify the underlying source of impact and validate potential remediation options. Additionally, we're continuing to assess the scope of impact and monitor for additional affected scenarios."  This is not an isolated event for **Exchange Online**. The service has faced multiple outages in recent months. In June, **Microsoft** addressed a widespread issue affecting the mail flow pipeline for customers across North America, Asia-Pacific (APAC), and Europe. April saw the resolution of **Exchange Online** mailbox access issues impacting **Outlook** mobile and macOS users, as well as another outage that blocked access to mailboxes via various **Exchange Online** connection protocols.