Microsoft Exchange 2019 On-Premises Claude MCP

An MCP server that connects Claude (claude.ai, Claude Desktop, Claude Code) to on-premises Microsoft Exchange (via EWS) and Active Directory. Users can book meeting rooms, check colleagues' free/busy, manage calendar events and handle email in natural language.

Users sign in with your OpenID Connect provider (tested with Keycloak). The server validates their JWT and acts as them in Exchange through one service account with ApplicationImpersonation, so no user password ever reaches the server.

Language: replies are in English by default; set UI_LANGUAGE=fa for Persian (Farsi). Times are handled in Iran Standard Time (UTC+03:30), which is easy to change: see Customizing.

Features

• Safe booking. Every booking is two steps: a preview, then confirmed=true. The schema requires it. Free/busy is checked for the organizer, attendees and room, and checked again on confirm. Dates are resolved server-side, so a stale date from the model is visible to the user before anything is sent. Past dates are rejected.

• Room verification with rollback. After booking, the server polls the room's own calendar until it holds a meeting with the same calendar:UID. If the room declined (a race or a booking policy), the meeting is deleted by ItemId.

• Recurring meetings: daily, weekly and monthly series. Availability is checked for every occurrence, and one conflict refuses the whole series.

• Room access control: restrict a room to members of an AD group. Nested groups are checked with LDAP_MATCHING_RULE_IN_CHAIN, and the check fails closed.

• Org-chart aware: book a meeting with your team or your direct reports, and look up managers through LDAP.

• Email: list, read, send and reply, plus attachment download links.

• Persian-aware user search: normalizes Arabic/Persian letter variants.

Tools

Related MCP server: Outlook MCP Server

Architecture

Claude (connector / Claude Code)  ── Authorization: Bearer <OIDC JWT> ──►  reverse proxy (TLS)
                                                                             ├─ /       → 127.0.0.1:3000  index.js (MCP, Streamable HTTP)
                                                                             └─ /auth/  → 127.0.0.1:3001  login-server.js
index.js ── EWS SOAP / NTLM / ExchangeImpersonation ──► Exchange (EWS)
index.js ── LDAPS ─────────────────────────────────────► Active Directory
index.js ── JWKS verify ───────────────────────────────► OIDC provider

The server publishes /.well-known/oauth-protected-resource and /.well-known/oauth-authorization-server, so MCP clients discover the OAuth login automatically.

Requirements

• Node.js 20+

• Exchange 2016/2019 with EWS enabled

• A service account with the ApplicationImpersonation role, which is also used to bind to LDAP

• An OIDC provider. Users' tokens must carry an email claim that matches their Exchange primary SMTP address.

• A reverse proxy with TLS, such as nginx (see deploy/nginx.conf.example)

Setup

git clone https://github.com/shahmirdelfanazari/Microsoft-Exchange-2019-ON-Premises-Claude-MCP.git
cd Microsoft-Exchange-2019-ON-Premises-Claude-MCP
npm install
cp .env.example .env              # fill in your values
cp rooms.example.json rooms.json  # list your room mailboxes
# optional: copy your AD CA certificate to ./ldaps-ca.pem
npm start

Exchange

New-ManagementRoleAssignment -Name "mail-mcp-impersonation" `
  -Role ApplicationImpersonation -User svc-mail-mcp

Room mailboxes should be auto-accept resource mailboxes.

OIDC client (Keycloak)

• Client ID mail-mcp (or whatever you set in OIDC_CLIENT_ID), standard flow, PKCE S256.

• Redirect URIs: http://localhost* (Claude Code) and https://<PUBLIC_URL>/auth/oauth-callback.

• Turn Advanced → OpenID Connect Compatibility Modes → "Exclude Issuer From Authentication Response" ON. MCP clients enforce RFC 9207, and this server advertises itself as the issuer. Without this setting, login fails with Issuer mismatch in authorization response.

Rooms (rooms.json)

{
  "rooms":      [{ "email": "room-a1@example.com", "name": "A1 (6-8 people)" }],
  "restricted": { "room-exec@example.com": "exec-room@example.com" },
  "excluded":   ["room-other-building@example.com"],
  "sizeGuide":  "2 people→A2, 3-4→B1, 6-8→A1"
}

• rooms is the fallback list, used when Exchange has no room lists. It also supplies display names.

• restricted maps a room to an AD group (by mail or sAMAccountName); only members can book it. If the group is missing, nobody can book the room.

• excluded lists rooms that are never bookable.

• sizeGuide is shown to the model.

Running in production

Use pm2 with deploy/ecosystem.config.cjs.example, and run a single process (MCP sessions live in memory). Bind the server to localhost only and expose it through the reverse proxy.

Connecting Claude

• Claude Code: claude mcp add exchange --transport http https://mail-mcp.example.com/mcp

• claude.ai / Claude Desktop: add a custom connector pointing at https://mail-mcp.example.com/mcp.

Customizing

• Timezone: Iran time (fixed +210 minutes, no DST) is used in nowIran(), isPastDateTime(), iranLocalToMs(), get_current_time and the availability request (Bias=-210). Change these for another zone.

• Work week and hours: isWorkDay() (Friday off), WORK_START_HOUR and WORK_END_HOUR in index.js.

• Language: every user-facing string lives in locales/en.js and locales/fa.js. UI_LANGUAGE chooses which one is used. To add a language, copy locales/en.js (keep every key), translate it, and register it in i18n.js.

Security

Read SECURITY.md before deploying. In short: the service account can read every mailbox, so keep the server on your internal network and keep .env readable by root only.

License

MIT