multi-email-mcp — multi-account mail MCP server

A small local MCP server (stdio) that gives Claude unified read-only access to any number of email accounts at once — Gmail and Microsoft 365 — each authenticating independently, all exposed through one connection.

Setting this up for the first time? Start here → CLIENT-ONEPAGER.md — a plain-English walkthrough (install, connect your accounts, done). The rest of this README is the technical reference.

Docs map: CLIENT-ONEPAGER.md (start here) · CLIENT-SETUP.md (per-account steps + IT request templates) · DAILY-BRIEFING.md (automate a daily briefing) · CLIENT-NOTE.md (what it is, in plain terms).

Providers (per account, set in .env)

Why app passwords first? For accounts you control they need no Google Cloud project, no consent screen, no token storage — just 2-Step Verification plus one generated password. The tradeoffs: an app password is a full-access mailbox credential, and hardened orgs disable them — that's what the two OAuth providers are for. Microsoft has no app-password lane at all (basic IMAP auth was retired in 2022–2024), so Outlook accounts always use Graph.

Related MCP server: Gmail MCP Server

Tools

account: "all" fans out to every account in parallel and merges results newest-first; a failing account comes back as an errors entry instead of failing the call. Result shape is identical across providers.

Setup

1. npm install

2. cp .env.example .env, list your accounts (see comments in the file)

3. Per account: paste an app password, or npm run auth <id> for the OAuth providers (one-time interactive sign-in; tokens cached in tokens/, git-ignored). Step-by-step per lane: CLIENT-SETUP.md — including the IT request templates for locked-down orgs.

4. npm run check — verifies every account end-to-end and prints counts.

Adding an account

Append an id to MAIL_ACCOUNTS, add its MAIL_<ID>_* vars, auth if OAuth. No code changes.

Wiring into Claude

Claude Code:

claude mcp add --scope user mail -- node /path/to/multi-email-mcp/src/server.js

Claude Desktop (claude_desktop_config.json):

{ "mcpServers": { "mail": { "command": "node", "args": ["/path/to/multi-email-mcp/src/server.js"] } } }

.env and tokens/ are resolved relative to this folder, so launch cwd doesn't matter.

Security notes

• .env and tokens/ are git-ignored; nothing secret is ever committed.

• Read-only by construction: IMAP mailboxes open with a read-only lock, and the OAuth scopes requested (gmail.readonly, Mail.Read) cannot send, modify, or delete even if the code tried.

• The MCP server is headless — it never opens an interactive auth flow; if a token is missing or revoked it returns an error telling you to run npm run auth <id>.

• Revocation per lane is documented in CLIENT-SETUP.md.