# 📮 mailbridge **The email MCP server — give Claude, Codex, Cursor or any AI agent a real mail client for iCloud, Outlook, Gmail, QQ, 163 and any IMAP mailbox.** **English** | [简体中文](README.zh-CN.md) ![Python](https://img.shields.io/badge/python-3.9%2B-blue) ![Dependencies](https://img.shields.io/badge/dependencies-zero-brightgreen) ![Protocol](https://img.shields.io/badge/protocol-MCP-8A2BE2) ![License](https://img.shields.io/badge/license-MIT-green) ![i18n](https://img.shields.io/badge/lang-EN%20%2F%20中文-orange)

Search, read, draft, send, file, and bulk-export mail across every mailbox you own — in conversation. Written in pure Python with **zero third-party dependencies**: no `pip install`, no build step. If a Python 3.9+ interpreter exists, it runs. ## Why Most agent platforms' built-in connectors cover Gmail and Microsoft 365 work accounts. They do not cover personal iCloud, personal Outlook.com, QQ, 163, or your own IMAP server — and a search connector is not a mail client. mailbridge adds the missing operations: attachments, folders, real sending, bulk export. It speaks plain MCP over stdio, so the same server works in Claude, Codex, Cursor, Cline, Gemini CLI — anything that can launch an MCP server. | Provider | Method | Credential | |---|---|---| | iCloud Mail | IMAP/SMTP | App-specific password | | Gmail | IMAP/SMTP | App password | | QQ / 163 / 126 | IMAP/SMTP | Authorization code (授权码) | | Yahoo / Fastmail / custom | IMAP/SMTP | Provider app password | | Outlook.com / Hotmail | Microsoft Graph | Free Entra app registration (OAuth) | | Work / school Exchange | Microsoft Graph | Same registration + tenant consent | ## Quick start ```bash git clone https://github.com/henry200803/mailbridge.git python mailbridge/server/setup.py # interactive wizard: add accounts, sign in, test ``` Then register the server with any MCP client: ```jsonc // Claude Desktop (claude_desktop_config.json), Cursor, Cline, … { "mcpServers": { "mailbridge": { "command": "python", "args": ["/path/to/mailbridge/server/server.py"] } } } ``` ```bash # Claude Code claude mcp add mailbridge -- python /path/to/mailbridge/server/server.py ``` ```bash # Codex CLI codex mcp add mailbridge -- python /path/to/mailbridge/server/server.py ``` Cowork users: install the packaged `.zip` through the plugin installer instead — the bundled `.mcp.json` wires everything up. ## Microsoft accounts need a (free) client ID Microsoft retired password-based IMAP/SMTP, so Outlook.com / Hotmail and work/school mailboxes connect through Microsoft Graph with OAuth — which requires an **Entra app registration**. Most personal users don't have one yet. It is free (no Azure subscription), takes about five minutes in a browser, and **one registration covers every Microsoft mailbox you own**. Follow the step-by-step guide — **[Registering a Microsoft app for mailbridge](skills/mail-setup/references/azure-app-registration.md)** — then paste the resulting *Application (client) ID* into the setup wizard. The guide also covers tenant values, every common `AADSTS` error, and the university-mailbox consent problem. Your client ID stays in your local `accounts.json`; it is configuration for your own registration, and this repository ships none. ## Tools | Tool | Purpose | |---|---| | `mail_list_accounts` | What mailboxes exist and whether they work | | `mail_list_folders` | Folder tree with unread/total counts | | `mail_search` | Filterable search across one or all accounts | | `mail_get_message` | One message in full, HTML converted to text | | `mail_get_thread` | The whole conversation | | `mail_digest` | Cross-account unread review in one call | | `mail_download_attachment` | Save an attachment to disk | | `mail_export` | Bulk search results to CSV / JSON | | `mail_draft` | Save a draft, threaded to a reply if asked | | `mail_send` | Send immediately — requires `confirm=true` | | `mail_mark` | Read/unread, flagged/unflagged, in bulk | | `mail_move` | File messages into a folder | | `mail_delete` | To Trash by default; permanent needs `confirm=true` | | `mail_auth_status` | OAuth health for Microsoft accounts | ## Bilingual 🇬🇧🇨🇳 Tool descriptions, the setup wizard, and provider hints ship in English **and** Simplified Chinese. Switch any time: ```bash python server/setup.py lang zh # or: lang en ``` or set the `MAILBRIDGE_LANG=zh` environment variable in your MCP client config. English is the fallback for anything untranslated. ## Cloud & portable mode Credentials normally live in `~/.mailbridge/` on the machine running the server. On ephemeral machines — cloud sandboxes, containers — ship them **inside the bundle** instead: put a `.mailbridge/` directory (the same `accounts.json` + `tokens/`) next to `server/`. Resolution order: `MAILBRIDGE_HOME` env → `~/.mailbridge` (when configured) → bundled `.mailbridge/` so a bundle with baked-in credentials still defers to the local config on your own machine. > ⚠️ A bundle containing credentials **is a secret** — never publish or share it. If one leaks, app passwords and the Entra registration are individually revocable. ## Security - Credentials live **only** in `~/.mailbridge/accounts.json` (mode 0600) on the machine running the server. Nothing is transmitted anywhere except to your mail provider. - No password ever passes through the conversation transcript — the wizard reads it with hidden input. - App passwords and the Entra registration are individually revocable: delete one and mailbridge is cut off instantly. - Sending and permanent deletion are gated behind an explicit `confirm=true` argument. ## Known limits - Graph (Outlook/Exchange) attachments are supported up to 150 MB via chunked upload sessions; the provider's total-message-size limit still applies, as it does on every IMAP provider (typically 20–50 MB per message). - IMAP full-text search is server-side; some providers (notably QQ) silently return nothing for non-ASCII search terms — filter by sender or date instead. - `mail_get_thread` on IMAP matches normalised subjects rather than true threading headers; Graph accounts use real conversation ids. - Most universities block third-party apps until IT approves the Entra registration — that is tenant policy, not something mailbridge can route around. ## Layout & tests ``` server/ MCP server (stdio JSON-RPC), IMAP + Graph backends, OAuth, i18n skills/ agent workflow guides: mailbox setup & everyday mail handling tests/ offline suite — no network, no credentials ``` ```bash python tests/test_mailbridge.py ``` ## Credits Built by **Sibo Huang**. Developed with **Claude Opus 5** (initial implementation, in Cowork) and **Claude Fable 5** (live testing, bug fixes, bilingual i18n, release engineering). ## License [MIT](LICENSE) © 2026 Sibo Huang