Microsoft Outlook and Teams were down for more than 12 hours, disrupting work at companies and government agencies worldwide, Reuters reported on Nov. 13.

Microsoft pointed to a server issue as the cause, the report said. The outage also affected the AI assistant Copilot.

The company said systems were stabilising as it expanded the rollout of a software fix. It added it had not identified malicious activity.

The outage was concentrated in the cloud service Exchange Online, an email and calendar management service. Only functions connected to that service were halted, while other apps continued to operate normally.

Organisations that run Microsoft services on their own servers were relatively less affected, Reuters reported.

The incident was the second service outage this year and one of the longest in Microsoft's history.

Disruptions spread to government agencies in Australia, Japan and the United States. In Britain, the National Health Service and the London Metropolitan Police were affected. The London Metropolitan Police faced disruption to some online crime reporting. Regional NHS organisations had to use alternatives such as paper records.

Companies were also affected. Euronext, the European exchange operator, experienced an email outage. British insurer Aviva used a backup system to conduct an earnings conference call.

OpenAI and Anthropic had problems with connectors that link their AI to Microsoft services.

Indian airlines including IndiGo, Akasa Air and Air India faced disruption to email-based customer support. One Taiwanese financial firm cancelled a bond repurchase transaction, and another confirmed a deal by fax, sources said.

U.S. electric truck maker Workhorse Group delayed its earnings release to the 16th. Switzerland's Richemont also briefly delayed its first-half earnings release.

Josh Gilbert (조시 길버트), a market analyst at eToro, said, "If reliability issues keep happening, IT departments will think twice before placing more of their work with one provider." Some analysts think Microsoft customers will not find it easy to switch to rivals because conversion costs are high.