Microsoft Investigates Exchange Online Outage Disrupting Mailbox Access

Microsoft is investigating a critical Exchange Online issue that is disrupting mailbox access for some users. The incident, tracked as EX1256020, has been intermittently affecting services since Thursday, with no confirmed resolution timeline yet.

Issue impacts Outlook mobile and Mac users

According to reports, the outage primarily affects Outlook mobile apps and the new Outlook for Mac. Users have experienced intermittent problems accessing their mailboxes, suggesting a backend service disruption rather than a client-side issue.

Microsoft has not disclosed how many users are impacted or which regions are affected. However, the classification of the issue as a critical incident indicates a noticeable and widespread service impact.

Root cause linked to virtual account change

Microsoft identified the root cause as a newly introduced virtual account within its infrastructure. Initial attempts to resolve the issue by restarting affected systems did not succeed, pointing to a deeper configuration problem.

As a result, the company has started rolling back the change across affected environments. This rollback is currently the primary mitigation strategy aimed at restoring normal service functionality.

No clear timeline for full recovery

While Microsoft continues to disable the problematic virtual account change, the company has not provided an estimated timeline for full resolution. Users may continue to experience intermittent access issues until the rollback process is fully completed.

Ongoing concerns across Microsoft services

This incident adds to a series of recent Microsoft-related concerns. Azure Monitor was recently exploited in phishing campaigns, while a critical SharePoint vulnerability is reportedly under active attack.

In parallel, Microsoft is also working on new improvements, including Priority Cleanup V2, a feature designed to enable faster online deletions across its services.

Microsoft says it will continue monitoring the situation and provide updates as mitigation efforts progress.

Via Bleeping Computer