mail-mcp

A local MCP server that lets AI coding agents (Claude Code and OpenAI Codex CLI) access your mailboxes: search, read messages/threads, read & download attachments, and create drafts — across multiple Gmail and personal Outlook accounts, routed by nickname.

Current capability: read-only + drafts. It never sends, deletes, or relabels mail. Sending/organizing are declared in the provider contract but gated off; enabling them later is a config change, not a rewrite (see Extending).

How safety is enforced

• Outlook (Graph): we request Mail.Read + Mail.ReadWrite but not Mail.Send, so sending is impossible at the token level.

• Gmail: there is no scope that grants drafts without also granting send (gmail.compose covers both). So for Gmail, "no send" is enforced at the application layer — no send tool is exposed and drafts.send/messages.send are never called. Keep this in mind before granting the send capability.

Related MCP server: Gmail MCP Server

Install

Requires Python ≥ 3.11.

uv venv --python 3.12 .venv
uv pip install --python .venv/bin/python -e ".[dev]"

Configure

.venv/bin/mail-mcp init            # creates ~/.config/mail-mcp/{config.toml,secrets,tokens,downloads}

Edit ~/.config/mail-mcp/config.toml (see config.example.toml). Each mailbox is one [accounts.<nickname>] block. Everything lives under $MAIL_MCP_HOME (default ~/.config/mail-mcp); set MAIL_MCP_HOME to relocate it.

Gmail OAuth (per Google account)

1. Google Cloud Console → new project → enable the Gmail API.

2. OAuth consent screen → User type External → add each Gmail address as a Test user (or publish to Production to avoid the 7-day refresh-token expiry in Testing mode).

3. Credentials → Create OAuth client ID → Desktop app → download the JSON → save as ~/.config/mail-mcp/secrets/gmail_client_secret.json (the same client can serve multiple Gmail accounts).

4. .venv/bin/mail-mcp auth gmail-personal

University / Workspace accounts (e.g. @g.ecc.u-tokyo.ac.jp): the admin may restrict third-party API access. If login fails with Error 400: admin_policy_enforced, your self-made client is blocked at the org level — Testing mode does not bypass this; only the Workspace admin can allowlist the client ID. Test a personal @gmail.com account first to confirm your setup, then try the university one.

Outlook OAuth (personal account)

1. Azure Portal → Microsoft Entra ID → App registrations → New. Supported account types: Personal Microsoft accounts only.

2. Authentication → Add platform Mobile and desktop applications → redirect http://localhost → mark as a public client.

3. API permissions → Microsoft Graph → Delegated → add Mail.Read, Mail.ReadWrite, offline_access. Do not add Mail.Send.

4. Put the Application (client) ID into the outlook block's client_id.

5. .venv/bin/mail-mcp auth outlook

Check status any time: .venv/bin/mail-mcp accounts

Register with your AI client

Both launch the server over stdio. Use an absolute interpreter path and set MAIL_MCP_HOME explicitly so token discovery never depends on cwd or env forwarding.

Claude Code (user scope — available in every project):

claude mcp add --scope user mail \
  --env MAIL_MCP_HOME=/Users/<you>/.config/mail-mcp \
  -- /path/to/mail_mcp/.venv/bin/python -m mail_mcp

Codex CLI — add to ~/.codex/config.toml (Codex does not forward parent env by default, hence env_vars):

[mcp_servers.mail]
command = "/path/to/mail_mcp/.venv/bin/python"
args = ["-m", "mail_mcp"]
env_vars = ["HOME", "PATH"]

[mcp_servers.mail.env]
MAIL_MCP_HOME = "/Users/<you>/.config/mail-mcp"

Verify: claude mcp list (shows mail ✓ Connected) / Codex /mcp.

Tools

Extending

• A new mailbox of an existing type → add an [accounts.<nick>] block + mail-mcp auth <nick>. No code.

• A new mailbox type (e.g. IMAP) → implement MailProvider (src/mail_mcp/providers/base.py) and register it in providers/registry.py. The tool surface is unchanged.

• Enable sending → add "send" to an account's capabilities. The send_message tool then registers automatically. For Graph, also add Mail.Send and re-run mail-mcp auth; Gmail needs no scope change. (Re-read the Gmail safety note first.)

Development

.venv/bin/pytest        # unit tests (no network)
.venv/bin/ruff check .
.venv/bin/mypy src