rubit-mcp-mail

rubit-mcp-mail

A read-only MCP server for reading your mail. Provider-agnostic: it speaks IMAP, so it works with Outlook.com, Gmail, Fastmail, iCloud, or a self-hosted server — the provider is a line of config, not a code change.

Read-only by construction. Folders are opened with EXAMINE, never SELECT, and bodies are fetched with BODY.PEEK, so reading a message does not even mark it as read. There are no send, move, delete, or flag code paths, and a test asserts none are ever added.

📖 Full documentation: https://bgalmes.github.io/rubit-mcp-mail/

Quick install

Download the installer for your system from the latest release and run it:

Nothing needs to be installed beforehand: Python and every dependency are inside that one file. A window asks for your provider and email address, signs you in, and registers the mail server with Claude Desktop and Claude Code if it finds them — restart Claude Desktop afterwards and your mail is there. It also leaves you a rubit-mcp-mail Settings shortcut for everything you want to change later. No terminal, at any point.

There is no macOS installer; on a Mac, install from source (below).

A note on antivirus warnings. Windows Defender or Avast may flag this .exe. This is a known false positive common to unsigned PyInstaller-built applications, not anything this project's code does — see the install guide for what to do about it. Every published SHA-256 is listed on the changelog.

Tools

Folders are addressed by role — inbox, sent, drafts, junk, trash, archive — so you never need to know that Outlook calls it Junk Email while Gmail calls it [Gmail]/Spam. Raw folder names work too.

Full arguments and return shapes: Tools reference.

Install with pip

If you already have Python 3.11+ and would rather not run an installer:

pip install rubit-mcp-mail
rubit-mcp-mail install      # the same setup wizard, from the terminal

Install from source

cd /path/to/rubit-mcp-mail
conda create -p ./.venv python=3.12 pip -y     # this machine has no python3-venv
./.venv/bin/python -m pip install -e .

Then configure an account, rubit-mcp-mail auth <account>, and rubit-mcp-mail doctor. The Windows variant and the full walkthrough are in Install from source.

Setting up a mailbox

Microsoft has retired basic auth for Outlook.com, so Outlook needs a free Azure app registration — seven steps, done once, written out in Setting up Outlook. Everything else takes an app password:

[accounts.personal]
provider = "generic"
email    = "you@fastmail.com"
host     = "imap.fastmail.com"

Known hosts: Gmail imap.gmail.com, Fastmail imap.fastmail.com, iCloud imap.mail.me.com, Yahoo imap.mail.yahoo.com. Gmail and iCloud require an app-specific password, not your login password.

Can't register your own Azure app?

If your Microsoft account genuinely can't register one, you can use the public client ID that other open-source mail tools already share for this purpose — Thunderbird's, 9e5f94bc-e8a4-4e73-b8be-63364c29d753. Paste it in as client_id. The consent screen will say "Thunderbird", and because the ID is outside our control Microsoft could rotate it. Details and caveats: Can't register your own app?.

Permissions

Any account-scoped tool can be forbidden for a given account with disabled_tools in config.toml, or by unticking a box on the settings window's Permissions tab. A blocked call returns a plain Error: ... string to the model rather than failing silently. See Permissions.

Registering with Claude

claude mcp add rubit-mail --scope user -- "$(pwd)/.venv/bin/rubit-mcp-mail" serve

Claude Desktop needs a JSON entry instead, and on Linux it needs the session environment passed explicitly or the keyring is unreachable — Register with Claude has both, and Troubleshooting has the logs.

Agent skill

skills/rubit-mail/SKILL.md tells an agent when to reach for the mail tools and how to chain them, and reminds it that the server is read-only and that mail content is untrusted. For Claude Code, copy it into your user (or a project's .claude/) skills directory:

mkdir -p ~/.claude/skills && cp -r skills/rubit-mail ~/.claude/skills/

Any other agent that reads SKILL.md files works the same way. See Agent skill.

Development

ruff check .
ruff format --check .
pyright
pytest -q

Those are the same checks CI runs. Commit messages follow Conventional Commits and drive automatic versioning — see CONTRIBUTING.md and AGENTS.md. Building the installers and adding a provider are covered in Contributing.

The website

website/ holds the documentation site (Nuxt), deployed to GitHub Pages by .github/workflows/deploy-website.yml. It is the source of truth for the docs; this README is deliberately the short version.

[!IMPORTANT] Website commits must not use feat: or fix:. python-semantic-release parses the commit type, not the scope, so feat(site): … would bump the Python package and cut an installer release. Use docs(site):, chore(site): or ci(site):.

Layout

src/rubit_mcp_mail/
  server.py        MCP tool definitions
  __main__.py      CLI: serve | install | auth | doctor | gui
  installer.py     setup wizard: writes config, signs in, registers with Claude
  installer_gui.py the setup window (tkinter), falling back to the terminal
  shortcuts.py     Start Menu / Desktop / .desktop entries for the GUI
  claude_registration.py  claude_desktop_config.json / `claude mcp add`
  session.py       wires config + auth + backend; attachment path safety
  config.py        TOML config -> Account models
  diagnostics.py   the doctor checks, as data (shared by the CLI and the GUI)
  permissions.py   registry of per-account-toggleable tool names
  config_editor.py every write to config.toml: comment-preserving, validated
  config_gui.py    the settings window (tkinter): accounts, permissions, doctor
  providers.py     provider profile registry
  secrets.py       keyring with 0600-file fallback
  models.py        pydantic models + message handles
  mime.py          BODYSTRUCTURE walking, decoding, HTML->text
  backends/
    base.py        MailBackend protocol
    imap.py        the IMAP implementation
  auth/
    password.py         app passwords
    oauth_microsoft.py  MSAL device-code flow
skills/rubit-mail/SKILL.md  agent skill: when and how to use the tools
website/           the documentation site (Nuxt); see "The website" above

Releasing

Every merge to main prepares a release PR carrying only the pyproject.toml and CHANGELOG.md diff; a maintainer merges it by hand, which publishes the prerelease and builds the installers; promote-release.yml is dispatched manually to drop the -rc.N suffix. The human merge is load-bearing — GitHub raises no events for anything GITHUB_TOKEN does. Full flow: CONTRIBUTING.md and How releases work.

Notes and limits

IMAP search is substring-based, bodies are truncated at 20,000 characters, only text parts are downloaded, and Microsoft is actively tightening third-party mail access. The details are in Notes and limits.