REDMOND, Washington: Businesses and governments around the world were cut off from email, calendars and virtual meetings for more than 12 hours after an outage hit Microsoft's Outlook and Teams on November 13, pushing some organizations back to fax machines and halting at least one bond repurchase in Europe.

Microsoft said server issues were behind the incident, which also affected its Copilot AI assistant, and that a broader roll-out of software fixes was starting to stabilize the system. It said it was not aware of any malicious activity.

The outage is one of the longest in Microsoft's history and the second disruption to its services this year. Microsoft said it specifically hit features tied to Exchange Online - its cloud-based email and scheduling hub - leaving unconnected applications operational.

Outlook and Teams are two of the most widely used workplace applications with hundreds of millions of users. The outage affected government agencies from Australia to Japan and the United States, caused delays at trading firms, hindered some companies from publishing earnings and prompted airlines to warn customers of communication lags, according to public statements.

European exchange operator Euronext reported email disruptions, British insurer Aviva activated backups for its earnings calls and Danish shipping giant Maersk warned customers of delayed updates. American AI giants OpenAI and Anthropic also faced issues with Microsoft connectors.

The outage also disrupted fund management at Taiwanese securities firms, life insurers, and investment trust companies. One of the companies went as far as cancelling a bond repurchase transaction, a source familiar with the situation told Reuters. Another Taiwanese financial company resorted to using fax to confirm trades, a second source said.

In the US, electric truck maker Workhorse Group rescheduled its results on November 12 to November 16, while Switzerland's Richemont briefly delayed its first-half results announcement on November 13.

A spokesperson for the UK government said it was working with Microsoft to find a solution for the outage that hit organizations such as the NHS and London's Metropolitan Police. In Australia, where the spy agency and federal police were among organizations caught in the outage, Cyber Security Minister Tony Burke said Microsoft does not suspect a cyber attack.

The incident deepens questions about the global reliance on a handful of Big Tech companies that supply both the essential software and the cloud infrastructure that underpins it.

Microsoft also faced an outage with its 365 services in January this year and in October last year. In October, it reported an outage of its Azure cloud platform that impacted its suite of productivity software, and a range of industries worldwide.

"The bigger worry is that this is not the first Microsoft 365 outage this year," said Josh Gilbert, a market analyst at trading platform eToro. "If reliability starts to look like a recurring problem, it hands every IT department a reason to think twice before putting even more of their business in one provider's hands."

Still, some analysts have questioned whether such incidents can push customers on to rivals due to the steep switching costs of replacing tools embedded so deeply in daily operations.

Disruptions and financial losses from the outage could result in numerous insurance claims, but the overall hit to insurers is expected to be limited, said Mario De Cicco, vice president of European financial institutions at Morningstar DBRS. De Cicco estimated global insured losses from the incident at between $300 million and $500 million, well below the $400 million to $1.5 billion financial toll from the 2024 CrowdStrike outage that crashed more than 8 million Windows-based computers and caused widespread disruptions.