Microsoft is investigating a new outage in Exchange Online preventing users from connecting to their mailbox in the classic Outlook desktop app.
The outage (EX1189820) was confirmed by Microsoft on Monday morning. Users in Asia and North America report that Outlook cannot connect to Exchange servers or completely freezes during login. Microsoft says it is actively working on the cause and states that only the classic version of Outlook is affected. The modern Outlook and web application continue to work as usual and are recommended as temporary solutions.
Outlook Search Function also Faltering
There is also a second incident (EX1189768) causing issues with the search function in classic Outlook. Users cannot see results or view colleagues’ availability. The latest update indicates that both errors have now been merged under EX1189768. This involves problems with: searching, availability overview, connection to Exchange Online, and setting Out of Office.
The problem began on November 19, 2025, when some users lost access to their mailbox. Microsoft quickly admitted that the error was in the backend infrastructure. On November 25, Microsoft reported that the rollout of the solution is 92 percent complete, and that’s where we still are at the time of writing.
Series of Outages in Recent Weeks
At the end of October, a DNS outage caused widespread downtime of Azure and Microsoft 365 services. In early November, Microsoft again faced Teams, Exchange, and admin center outages due to issues with Entra SSO and MFA.
Microsoft is working on a structural solution and promises further updates as soon as more is clear about the cause and recovery.