Microsoft 365 outage hit Teams and Exchange as UK police reliance exposed

Microsoft reversed a network change and worked to restore capacity while 46 of 48 UK police forces were found to route email through the cloud service. The Federal Office for Information Security said there were no indications of a cyberattack.

Correction: An earlier version named Azure; the sources speak of the Microsoft outage without naming Azure.

A Microsoft 365 outage began on Thursday 12 November and knocked out Exchange Online, Teams, SharePoint and other cloud services around the world. It first hit the United States and the Americas before spreading further. Computerweekly's DNS mapping shows 46 of 48 UK police forces route email through Microsoft 365. It also counts 47 of the 48 forces connected to at least one US hyperscaler.

"Over-reliance on a single provider leaves businesses and public services vulnerable to disruption and creates wider economic risks", said Nicky Stewart, senior advisor to the Open Cloud Coalition. She called the outage a reminder of the real economic and human costs of lock-in. She called greater diversity across cloud providers essential.

The outage began when certain servers failed their automated health checks and shut down, pushing their load onto the servers still online. That cascaded: a core process on the affected servers became overwhelmed, and capacity drained away. At 01:06 GMT on 13 November Microsoft reverted a network configuration change it had correlated with the start of the outage. It later said its mitigation changes were not taking as expected. It was working on alternate ways to add capacity amid sustained traffic imbalances.

Microsoft said on Friday, 13 November, that it had "no evidence of malicious activity associated with this incident". The Federal Office for Information Security (BSI) said there are no indications of a cyberattack in the outage.

Microsoft promised a full post-incident report once mitigation is complete, with the root cause and the defense-in-depth actions it plans to take. "We will continue to treat this with urgency until full mitigation," the company said. Microsoft said it had seen early signs of stabilisation, but service capacity had not yet returned to normal levels. Health remained variable as traffic was carefully reintroduced.