Microsoft is currently looking into a significant service disruption that is resulting in authentication difficulties, connection issues, delays in email delivery, and various other complications for users of Microsoft 365.
The company first acknowledged this situation (identified as EX1464935 in the admin center) at 5:30 PM UTC, following a surge of reports from users on social media about several problems affecting Exchange Online.
While Exchange Online is the service most severely affected, Microsoft has indicated in a recent incident report (MO1465074) that this outage is also impacting several other Microsoft 365 services, such as OneDrive for Business, SharePoint Online, Microsoft Teams, Microsoft Purview, and Microsoft Defender XDR.
According to Downdetector, an outage tracking service, tens of thousands of Outlook and Microsoft 365 users are experiencing difficulties with email reception through Outlook and accessing Microsoft cloud services.
The symptoms associated with Exchange Online outages, as reported by Microsoft, include:
- Delays or failures in sending or receiving email messages.
- Delays, failures, or incomplete results when searching for content within Exchange Online mailboxes.
- Errors related to authentication when trying to access Exchange Online services.
- Challenges in accessing or executing actions within Exchange administration experiences.
- Intermittent failures affecting mailbox operations and message delivery processes.
Although the company has not specified which regions are affected, it has categorized this outage as an incident, a term typically reserved for critical service issues that have a significant impact on users.
In the latest update from the admin center, Microsoft stated, “We have identified a common failure pattern across the affected Exchange Online requests that is linked to authentication and protocol connectivity.”
“We are analyzing service telemetry to pinpoint the root cause of the impact and to explore potential remediation options. Furthermore, we are continuously evaluating the extent of the impact and monitoring for any additional affected scenarios,” Microsoft added.
In recent months, Microsoft has dealt with several Exchange Online outages, the most recent being in June, when it addressed a widespread service issue that affected the mail flow pipeline for customers in North America, Asia-Pacific (APAC), and Europe.
In April, the company also resolved issues with Exchange Online mailbox access that had intermittently affected Outlook mobile and macOS users for several weeks, as well as an outage that prevented users from accessing their mailboxes through Outlook on the web, Outlook desktop, Exchange ActiveSync, and other Exchange Online connection protocols.
Update August 31, 14:29 EDT: Microsoft attributes the outage to issues with core authentication configuration.
“We have identified problems related to a core authentication configuration utilized by multiple internal services within the Exchange Online infrastructure,” Microsoft stated. “We are conducting manual tests at the individual server level to reset configurations and determine if this resolves the issue.”
Update August 31, 15:09 EDT: Microsoft is now tracking this outage under MO1465074 and has confirmed that the incident also affects OneDrive for Business, SharePoint Online, Microsoft Teams, Microsoft Purview, and Microsoft Defender XDR.
Once attackers gain valid credentials, only 37% of their actions are blocked. Overall prevention scores can obscure what occurs after initial access. Once attackers are operating with valid credentials, prevention effectiveness declines significantly.
The Blue Report 2026 evaluates defense techniques on a case-by-case basis across 338 million simulations conducted in customer production environments.
Get the report
Source: Original article
