MCP claude.ai Microsoft 365 connector rejects personal Microsoft accounts (Hotmail/Outlook.com/Live)

Summary

The bundled claude.ai Microsoft 365 MCP connector cannot authenticate personal Microsoft accounts (@hotmail.com, @outlook.com, @live.com). The OAuth flow halts at the Microsoft sign-in page with the error:

You can't sign in here with a personal account. Use your work or school account instead.

Reproduction

1. In Claude Code, run /mcp.
2. Select claude.ai Microsoft 365 → start auth flow.
3. Browser opens https://login.microsoftonline.com/common/oauth2/v2.0/authorize?response_type=code&client_id=08....
4. Enter a personal MSA email (e.g. name@hotmail.com).
5. Microsoft displays the rejection above before any consent screen is shown.

Expected

Personal Microsoft accounts (Outlook.com / Hotmail / Live) should be accepted, since the connector targets Outlook mail and OneDrive — both of which are first-class personal-account services. Many users' primary mailbox is @hotmail.com.

Likely root cause

Anthropic's OAuth app registration appears to use signInAudience = AzureADMyOrg or AzureADMultipleOrgs (work/school only) instead of AzureADandPersonalMicrosoftAccount. The /common endpoint accepts personal MSA only when the app's audience permits it.

Requested fix

Re-register (or update) the OAuth app with signInAudience = AzureADandPersonalMicrosoftAccount so both work/school and personal accounts can authenticate.

Reference: https://learn.microsoft.com/en-us/azure/active-directory/develop/supported-accounts-validation

Workarounds users currently need

• Forward Hotmail → a working provider (e.g. Gmail) and ingest via claude.ai Gmail MCP.
• Build a custom IMAP poller against imap-mail.outlook.com:993 using a Microsoft account app password.

Both are awkward and shouldn't be necessary for what is a primary consumer mail/storage product.

Environment

• Claude Code (CLI), Opus 4.7
• macOS 25.4.0 (Darwin)
• Browser: Chrome
• Affected MCP: claude.ai Microsoft 365 (claudeai-proxy at https://microsoft365.mcp.claude.com/mcp)
• Affected account type: personal MSA