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Thunderbird Cli

Connects AI agents to Thunderbird for local, credential-free email reading, searching, drafting, and management.

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Install Thunderbird Cli

Pick your client, then add it in one click or paste the config.

STDIONode.js
~/Library/Application Support/Claude/claude_desktop_config.json
claude_desktop_config.json
{
  "mcpServers": {
    "thunderbird-cli": {
      "command": "npx",
      "args": [
        "-y",
        "thunderbird-cli-mcp"
      ]
    }
  }
}

Settings → Developer → Edit Config, merge this into mcpServers, then fully quit and reopen Claude Desktop.

We couldn’t confirm it starts correctly

The install command started, but didn't respond the way we expected when we tried to talk to it.

npx -y thunderbird-cli-mcp

initialize succeeded but no response to tools/list.

This is an experimental automated check and can have false negatives — missing environment variables, a slow cold install, etc. It doesn’t necessarily mean something’s wrong. Last checked 8d ago.

Overview

The thunderbird-cli MCP server gives AI agents read/write access to email managed by Mozilla Thunderbird without exposing IMAP or SMTP credentials. It uses a signed Thunderbird extension, a local bridge daemon, and an MCP server that provides 12 curated email tools with JSON-compatible results. Use it when Thunderbird already holds your accounts and you need local agent workflows for searching, reading, drafting, replying, attachments, folders, or bulk operations. Thunderbird 128+, Node.js 20+, the CLI and bridge packages, and the extension are required.

Use cases

  • Check unread counts across Thunderbird accounts
  • Search messages by sender, date, or subject
  • Draft replies without exposing mail credentials
  • Download email attachments for local workflows
  • Move older messages between folders in bulk

Key features

  • 12 curated MCP email tools
  • 38 JSON-output CLI commands
  • Local Thunderbird credential handling
  • Draft-first compose, reply, and forward actions
  • Attachment and folder operations
  • Field selection and body truncation

Security & health

What it can reach and how reliably it runs — from our own checks, not the maintainer’s claims.

ActiveLast checked Today

Recent health check succeeded.

8/8 checks healthy over the last 45d

Supply-chain signal

No high-severity advisories surfaced by our automated scan.

Critical 0High 0Medium 0Low 0

Scanned 7d ago via OSV.dev · thunderbird-cli-mcp (npm)

Adoption & maintenance

Factual signals from GitHub, npm, and our automated checks — not a rating.

GitHub stars62Stargazers on the source repository.
npm downloads464Package downloads in the last 30 days.
Last commit1d agoMost recent push to the default branch.
Install checkInconclusiveStarted but did not complete the MCP handshake in our test.
Directory activity2 viewsConfig copies, upvotes, and views on AllMCPs.

How Thunderbird Cli works

What thunderbird-cli MCP server does

The thunderbird-cli MCP server exposes email stored and managed by Mozilla Thunderbird to AI clients through MCP. It can support common mailbox workflows including checking unread counts, searching messages, reading message content, composing drafts, replying, forwarding, handling attachments, changing folders, and performing bulk actions. The available MCP interface contains 12 curated tools; the companion command-line interface provides 38 commands for direct automation.

Thunderbird remains the source of truth for accounts, messages, and mail state. IMAP and SMTP credentials stay inside Thunderbird rather than being copied into an agent configuration or a separate mail library. This makes the server a fit for developers who already use Thunderbird and want machine-readable email access without maintaining another authentication flow.

How it works

The system has four parts. A Thunderbird WebExtension calls Thunderbird's messenger.* APIs. A local bridge daemon translates requests between HTTP and WebSocket connections. The tb CLI acts as a thin HTTP client and returns JSON, while the MCP package exposes selected email operations to compatible AI clients.

The thunderbird-cli MCP server does not cache or store email data. Its architecture is local-host oriented: the agent communicates with the local MCP entry point, the bridge communicates with Thunderbird, and Thunderbird handles the configured accounts. The repository describes the bridge as stateless and without business logic.

Draft-oriented behavior is used for potentially consequential actions. Compose, reply, and forward operations save drafts by default, while permanent deletion requires an explicit confirmation flag in the CLI. Output can be reduced with field selection, compact mode, and body-length limits to control the amount of message data returned to an agent.

Setup and configuration

Install the CLI and bridge globally with npm, then install the signed Thunderbird extension from the project's release page through Thunderbird's Add-ons interface. Start the bridge daemon with tb-bridge and verify the connection with commands such as tb health or tb stats.

For MCP use, configure the thunderbird-cli MCP server as a stdio entry using npx -y thunderbird-cli-mcp in the MCP client's server configuration. The documented example targets Claude Desktop. After restarting the client, the email tools can answer mailbox questions and perform supported operations through Thunderbird.

The documented runtime requirements are Node.js 20 or newer and Thunderbird 128 or newer. Additional repository documentation covers background services, Docker, troubleshooting, command details, and the MCP-specific setup.

Tools and capabilities

The supported workflows include:

  • Count unread messages and inspect mailbox statistics.
  • Search by terms and filters such as sender or date, with selected output fields.
  • Read messages with headers, text, and optional body truncation.
  • Compose, reply to, and forward messages as drafts by default.
  • Download attachments.
  • Create, modify, and manage folders through the CLI.
  • Move messages in bulk using filters such as sender or age.

The CLI emits JSON, which suits scripts and agent pipelines. The MCP layer selects a smaller set of curated tools rather than exposing every CLI command directly.

Limitations and notes

The server depends on a running local Thunderbird installation, the installed extension, and the bridge daemon. It is not a cloud mail service and does not replace Thunderbird's account configuration. Credentials remain managed by Thunderbird, so agents must use accounts already available there.

Localhost-only operation means the documented design keeps traffic on the machine and does not send email data to a hosted service. Actions that can change or remove mail should still be reviewed: drafts are the default for composition-related operations, but sending and other write actions can affect real accounts. Permanent deletion requires confirmation in the CLI.

The thunderbird-cli MCP server is licensed under MIT. The repository reports testing with 22 accounts and more than 249,000 messages, but that scale should not be treated as a guarantee for every Thunderbird setup.

Read the full README View source on GitHub

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Frequently Asked Questions about Thunderbird Cli

thunderbird-cli is an MCP server that connects AI agents to email managed by Mozilla Thunderbird through a local bridge and extension. Its main tools support mailbox statistics, message search and reading, drafting and replying, attachment handling, folder operations, and bulk email actions without exposing IMAP or SMTP credentials.

Install the required npm packages, add the signed Thunderbird extension, start the bridge daemon, and configure `npx -y thunderbird-cli-mcp` as an MCP server. The documented package installation is `npm install -g thunderbird-cli thunderbird-cli-bridge`; Node.js 20+ and Thunderbird 128+ are required.

Yes, thunderbird-cli works with Claude Desktop through a stdio configuration that runs `npx -y thunderbird-cli-mcp`. Add the server entry to Claude Desktop's configuration, restart the client, and ensure the Thunderbird extension and `tb-bridge` daemon are running.

No, the documented design keeps IMAP and SMTP credentials inside Thunderbird. The agent accesses the accounts through the Thunderbird extension and local bridge, while the CLI does not cache or store email data.

No, compose, reply, and forward operations save drafts by default according to the documented safety behavior. Permanent deletion requires confirmation in the CLI, but developers should still review write actions before they affect a live mailbox.

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