Microsoft Outlook was hit by a major outage on Thursday, leaving tens of thousands of users unable to reach their email. Outage-tracking site Downdetector recorded more than 65,000 reports of problems with Outlook by around 6.10pm, rising from about 2,400 at 5.50pm to 13,000 within eight minutes. Users reported trouble opening the website, logging in and using the app, and the disruption was especially widespread in the Americas, where some 60,000 people in the US were affected.

In the UK, more than 3,300 reports were logged within 20 minutes of the problem beginning just after 5.20pm. Users loading Outlook were met with a 'Failed to fetch' error, and when the website did load, inboxes sometimes appeared blank and emails would not send. Hundreds of people also struggled with Microsoft Teams and Copilot, the company's AI chatbot, while Microsoft's own service status checker was reported to be unavailable.S1S2

Microsoft first said it was investigating problems with mailboxes through multiple connection methods in the Americas, but later warned the issue may affect Microsoft 365 connectivity for users in any region. The company said a piece of infrastructure had become overburdened by the volume of requests and that it had begun redistributing connection traffic across its wider worldwide infrastructure to balance the load.S1S2

The outage came just days after Microsoft urged Outlook users to update their software to fix a security flaw that hackers were exploiting. Opening a specially crafted message file in an affected version of Outlook can trigger a connection to a criminal-controlled network location and expose sign-in information that could be used to impersonate victims. The fix was released in Microsoft's November 10 security updates, and users must update through an Office application such as Word via File, Account, Update Options and Update Now, since Windows Update alone is not enough. The US Cybersecurity and Infrastructure Security Agency has added the flaw to its catalog of known exploited vulnerabilities.S1