Security & Infrastructure Tools
Microsoft Exchange Online outage blocks access to mailboxes
Microsoft’s Exchange Online is experiencing an outage that blocks users from accessing mailboxes and calendars across all connection methods, including Outlook on the web, desktop, ActiveSync, and IMAP4. The issue was first reported at 06:42 UTC, with telemetry showing a decrease in incidents but customers still report problems. Additionally, Office.com’s web portal is down, displaying an error message, and a separate outage affecting Microsoft Copilot sign‑in pages and chat services is underway. Microsoft is working on configuration changes to resolve these disruptions.
Microsoft’s Exchange Online service has been experiencing a significant outage that is preventing users from accessing their mailboxes and calendars across multiple connection methods. The issue was first reported by Microsoft at 06:42 AM UTC, with the company acknowledging that “some users are experiencing problems when trying to access their Exchange Online mailbox via one or more connection methods.”
The outage affects Outlook on the web, Outlook desktop, Exchange ActiveSync, and other Exchange Online connection protocols. Despite telemetry indicating that the problem is no longer occurring for affected users, engineers continue to monitor service health to determine whether additional actions are required to ensure sustained recovery. Customers have continued to report difficulties accessing their email, and the Office.com web portal was briefly down, displaying a message asking users to refresh the page in a few minutes.
In addition to the Exchange Online outage, Microsoft is investigating a separate issue affecting the Microsoft 365 Copilot web sign‑in page and Copilot web clients at office.com/chat, m365.cloud.microsoft, and copilot.cloud.microsoft. Users who need to use Microsoft Copilot are advised to switch to application-based services such as the Microsoft Copilot desktop app, Copilot in Microsoft Teams, or Copilot in Office apps.
Microsoft has identified that a section of service infrastructure is not processing traffic efficiently and is making configuration changes to remediate the impact. An admin center service alert (MO1253428) confirms this ongoing effort.
This situation follows previous outages: in January, an Exchange Online outage intermittently blocked users from accessing mailboxes via IMAP4; in November, a similar issue prevented access through the classic Outlook desktop client. Microsoft’s handling of these incidents shows a pattern of rapid investigation and remediation, but the current outage remains unresolved for many customers.
As the story develops, it is essential to stay informed about updates from Microsoft’s 365 admin center and to consider alternative methods for accessing critical email services until the service fully stabilizes.