Microsoft outlook outage: Reason why are Outlook, Microsoft 365 down today, OpenAI, Anthropic AI services hit too

Microsoft 365 outage, Outlook down: Outlook, Microsoft 365, AI assistant Copilot and Teams were down for thousands of US users on Thursday with the disruption also hitting connectors used by OpenAI's and Anthropic's AI services.

Microsoft said in a statement that its team has paused all deployments, is moving additional traffic off the affected infrastructure, and is restarting affected servers to return them to service, the company added.

What caused Microsoft 365, Outlook Outage?

Microsoft said earlier in the day it had fixed a Teams disruption affecting users in North America and that the impact had been fully resolved. The company later said the issue may also affect Microsoft 365 service connectivity for users in other regions.

OpenAI said it was investigating an issue with Microsoft connectors in which new connections may be broken and tools are not working as expected. Anthropic said it had identified an issue with an upstream provider affecting its Microsoft 365 connector.

Microsoft later explained that a portion of its infrastructure was “experiencing elevated load" — which it said was “likely contributing to the connectivity errors.” The company determined a number of servers were “unexpectedly unavailable” due to a problem that caused them to fail during automated checks.

In updates posted on social media, Redmond, Washington-based Microsoft said it was aware of users “experiencing issues accessing Exchange Online mailboxes through multiple connection methods in the Americas.”

Microsoft did not immediately provide more information around what might be causing that failure, but added that it was testing a fix.

Earlier in the day, the company said it had “successfully restored” problems related to Microsoft Teams in North America, although some users continued to report connectivity issues.