Developing story, updated as details confirm.
What happened
Microsoft has been investigating a Microsoft 365 disruption since November 12, tracked as EX1550543 and MO1550821. @MSFT365Status first reported trouble accessing Exchange Online mailboxes through multiple connection methods in the Americas at 17:54 UTC on November 12 (1:54 a.m. November 13, Manila), then said Microsoft 365 connectivity may be affected in any region.
Microsoft said a core process on affected servers was becoming overwhelmed and that later changes “are not taking as expected.” As of 12:27 p.m. Manila on November 13, status.cloud.microsoft still showed a service degradation, and Microsoft’s 11:48 a.m. post said it was still reviewing traffic flows.
Anthropic says the same incident broke its Microsoft 365 connector: mail, calendar and search tools are still failing for most requests, and Claude for Outlook remains affected. Anthropic last updated status.claude.com at 22:23 UTC November 12 (6:23 a.m. Manila November 13) and lists the Claude API, Console and Claude Code as operational.
Who’s affected
Exchange Online and Outlook users in any region, and teams using Claude’s Microsoft 365 connector or Claude for Outlook.
What to do now
- Check status.cloud.microsoft and incident IDs EX1550543 and MO1550821 before changing Outlook, mailbox or connector settings.
- Give customers another channel, such as phone or a second email domain, until mail is reliable again.
- If you use Claude’s Microsoft 365 connector or Claude for Outlook, wait for the fix.
See our guide to Claude and Codex usage limits. More coverage is on our news page.
Sources & method
- Microsoft 365 Status (@MSFT365Status), EX1550543 / MO1550821 thread, November 12–13, 2026 — first post: https://x.com/MSFT365Status/status/2120938282204688468 ; later posts including 22:09 UTC November 12 (overwhelmed core process, https://x.com/MSFT365Status/status/2121002505911857577), 03:13 UTC November 13 (changes “not taking as expected,” https://x.com/MSFT365Status/status/2121079061774491735) and 03:48 UTC November 13 (latest at check time, https://x.com/MSFT365Status/status/2121087708940382422)
- Microsoft service health status — https://status.cloud.microsoft/
- Anthropic, Claude Status, “Elevated errors affecting the Microsoft 365 connector” (opened 17:52 UTC November 12, 2026; last update 22:23 UTC November 12) — https://status.claude.com/
Last checked: Nov 13, 2026, 12:27 p.m. Manila (UTC+8). Method: Facts come from Microsoft’s public status page and @MSFT365Status posts, and from Anthropic’s status page. We do not add a cause beyond what Microsoft has posted. Advice on checking the status page before changing settings, giving customers another channel, and waiting for the Claude connector fix is our own. No affiliate links. How we work.
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