--- title: "Massive Claude outage on November 13 linked to Microsoft 365 failure" description: "A massive Claude outage on November 13 was linked to a Microsoft 365 failure: authentication, Claude Code, and email integrations were affected. Anthropic has resolved the issue and the incident status is set to resolved." date: 2026-11-13T15:55:05.301Z lang: en url: https://xab.info/en/posts/claude-outage-linked-to-microsoft-365 tags: [claude, anthropic, microsoft-365, ai-outage, cloud-services] author: "Alexander Buran" publisher: "XAB.info" --- # Massive Claude outage on November 13 linked to Microsoft 365 failure ![Server rack with a monitor displaying cloud computing icons, a security lock, and error symbols](https://xab.info/media/2026/11/13/sboi-claude-sviazan-s-avariiej-microsoft-365/sboi-claude-sviazan-s-avariiej-microsoft-365-1.webp) ## Key Points - The November 13 Claude outage affected authentication for Claude.ai, Claude Code, and platform.claude.com - Anthropic stated that the cause of integration failures was a problem on the Microsoft 365 side - Tools for email, calendar, and search via the Claude connector worked with errors, and Claude for Outlook failed for some users - The problem has been addressed, and the incident status is set to resolved On November 13, 2026, users of the Claude AI platform experienced a massive outage affecting key services from Anthropic. According to the developer, the issues impacted authentication in the Claude.ai web interface and the Claude Code tool, as well as the operation of the developer platform platform.claude.com. The incident quickly drew community attention because Claude is actively used in both corporate and personal workflows, and its unavailability directly impacts users' daily routines. ### What exactly stopped working According to reports from Anthropic, the failure was not limited to a single component: users could not log in to Claude.ai accounts, start sessions in Claude Code, or access the API via platform.claude.com. This effectively disabled the "user-model" link for a significant portion of the audience. Separately, the company noted that tools for email, calendar, and search continued to work with errors via the Claude connector, and the Claude for Outlook add-in would not open at all for some users or failed to perform actions on emails and calendar events. ### Cause: Failure on the Microsoft 365 side In a separate clarification, Anthropic explicitly stated that the integration failure with Microsoft 365 was caused by a problem on Microsoft's end. This means the root cause was not in Claude's infrastructure, but in the dependency on external services within the Microsoft product suite. The company directed users to the official Microsoft 365 status page, where recovery updates are published, which allowed for real-time tracking of the incident and ensured it was not confused with internal AI platform failures. ### Recovery and incident status Upon completion of the work, Anthropic confirmed that the problem was resolved and the incident was given the status "resolved." This means authentication, Claude Code, the platform.claude.com site, and integration scenarios with Microsoft 365 have returned to normal operation. The company recommended that users check the Microsoft 365 status page if necessary to confirm the full recovery of third-party services on which the integrations depend. ### Context: Vulnerability to external dependencies The November 13 incident clearly demonstrated how modern AI products depend on the ecosystem of external services, even when the main computational engine is functioning correctly. Integrations with corporate tools — email, calendar, search — become a critical point of failure if their provider experiences an outage. For Anthropic, this is an additional argument for transparent communication: the company not only identified the failure but also publicly pointed to the source of the problem, directing users to the authoritative Microsoft 365 status source. ## Fact-Check & Sources - [Сбой Claude оказался связан с аварией Microsoft 365: Anthropic восстановила работу ИИ-сервиса](https://www.ixbt.com/news/2026/11/13/sboi-claude-okazalsia-sviazan-s-avariei-microsoft-365-anthropic-vosstanovila-rabotu-ii-servisa.html) - The primary source confirms: the outage affected authentication in Claude.ai and Claude Code, operation of platform.claude.com; the cause was an issue on the Microsoft 365 side; email/calendar/search integrations and Claude for Outlook worked with errors; the incident status is resolved; users were directed to the Microsoft 365 status page. ## FAQ ### What exactly did not work in Claude on November 13? According to Anthropic, the outage affected authentication in Claude.ai and Claude Code, as well as the platform.claude.com service. Tools for email, calendar, and search via the Claude connector worked with errors, and Claude for Outlook did not open for some users or failed to perform actions on emails and calendar events. ### What was the reason for the failure? Anthropic clarified that the integration failure with Microsoft 365 was caused by a problem on the side of Microsoft itself, meaning the root cause lay in external services rather than Claude's own infrastructure. ### Is the problem fixed? Yes. Anthropic confirmed that the problem was fixed, and the incident was given the status "resolved." To track the recovery of third-party services, the company directed users to the official Microsoft 365 status page.