Thunderbird MCP
A Thunderbird extension and MCP bridge: an agent searches mail, drafts replies and manages filters, contacts and calendars with 49 tools
- 443 ★ on the repository
- Last commit
- MIT
Broad access
Why this level
- The agent reads mail, attachments, contacts and the calendar, which hold personal and business data
- Tools delete messages and folders, empty trash and junk, and edit filters and contacts, and direct sending turns on with a setting
- The listen-on-all-interfaces option exposes the server to every device on the local network, though the session token stays required
Install
- Works in
Manual install
git clone https://github.com/TKasperczyk/thunderbird-mcp.gitThe repository holds a ready dist/thunderbird-mcp.xpi. Install it in Thunderbird through Tools, Add-ons, Install from file and restart.
Access and checks
How we reviewBroad accessThe tool can change data, run commands or handle secrets.
- The agent reads mail, attachments, contacts and the calendar, which hold personal and business data
- Tools delete messages and folders, empty trash and junk, and edit filters and contacts, and direct sending turns on with a setting
- The listen-on-all-interfaces option exposes the server to every device on the local network, though the session token stays required
This is third-party code. Review the repository files before installing.
What it does
Thunderbird MCP gives an agent access to the Thunderbird mail client. Inside Thunderbird an extension runs with a built-in HTTP server on localhost, and a Node bridge, `mcp-bridge.cjs`, translates MCP over stdio into requests to that server and finds the port and token from a connection file on its own. There are 49 tools in several groups. Mail: search by subject, sender, recipient, date and tags, read a message as Markdown, text or HTML, full headers, attachment search, flags, move, copy, delete, folder create and rename, and saved searches. Composing: a new message, reply and forward, a draft with attachments and delayed delivery, and a preflight check without sending. The agent also manages filters, contacts, calendars, events and tasks. Safety wins over convenience by default. Sending, replying, forwarding and creating an event open a review window, and direct sending is blocked by the "Block skipReview" setting until you turn it off yourself. Access can be limited by account and by tool, contact writes are off by default, and so is reading encrypted messages.
Who it is for. For people who keep mail, calendar and contacts in Thunderbird and want an agent to triage the inbox, find messages and prepare replies with a check before sending.
Good fit when
- You need to find messages by sender, subject and period in a big mailbox and get a short summary with its source
- You need to prepare a reply or forward with the quote and correct thread headers and check the text in a window before sending
- You need to triage the inbox: flag, file into folders, delete newsletters and set up filter rules
- You need to find mail with an attachment by file name or type and save the attachment to disk
- You need to read the schedule or create an event and a task in the Thunderbird calendar with confirmation in a dialog
Not a fit when
- You do not use Thunderbird: the extension needs a running client version 128 or newer
- You need automatic bulk sending with no human check: direct sending is blocked by default
- You need to work on a server with no graphical client: Thunderbird must be running on your computer
- Some mail must not be shown to a model: the tool reads messages and attachments of every mailbox you have not excluded in the settings
Example request
Find mail from accounting from the last month with PDF attachments, list it and prepare a reply with a question about the invoice in a window, without sendingMCP
- Transport
- stdio, http
- Authentication
- API key
Environment variables
THUNDERBIRD_MCP_CONNECTION_FILE- Path to connection.json if the environment uses a non-standard temp directory
Limitations
The extension needs a running Thunderbird 128 or newer, and the bridge needs Node. The server listens by default only on localhost, ports 8765 to 8774, and the session token sits in a `connection.json` file with mode 0600. The listen-on-all-interfaces option exposes the server to the whole local network, so turn it on only on a trusted network.
IMAP folders can hold stale data until you open the folder in Thunderbird. HTML-only messages are converted to plain text and lose formatting. IMAP folder operations are asynchronous, so verify the result with `listFolders`. Body search goes through the Gloda index and, without offline sync, searches headers only. A message read is limited to 50 MiB and 120 seconds. The extension installs from an unsigned xpi file, so a profile that requires signatures blocks both manual and automatic installs.
How to disable. Remove the `thunderbird-mail` entry from your MCP client configuration, for example `~/.claude.json`. In Thunderbird disable or remove the extension under Tools, Add-ons and Themes. Individual tools and accounts are switched off on the extension's settings page.
FAQ
How do I connect Thunderbird MCP to Claude Code?
Clone the repository and install `dist/thunderbird-mcp.xpi` in Thunderbird (Tools, Add-ons, Install from file), then restart. In `~/.claude.json` add a `thunderbird-mail` server with the command `node` and the absolute path to `mcp-bridge.cjs`.
Can the agent send mail without my knowledge?
No. The "Block skipReview" setting is on by default, so every send, reply and forward opens a review window. Direct sending can be turned on only by you in the extension settings, and for senders with encryption enabled it is still refused after that.
Can I limit which mailboxes the agent sees?
Yes. The extension settings page sets the list of accessible accounts, and each tool can be turned off separately. While an account restriction is active, calendars and address books stay closed until you allow them.
Does the agent read encrypted mail?
Not by default. While the encrypted-message read option is off, encrypted and opaque-signed messages are not decrypted, and attachment search does not reveal them.
What if recent messages are missing?
IMAP folders can lag. Open the folder in Thunderbird or run `refreshFolder`. If needed make the folder available offline so body search works.
Which port does the server use?
It tries ports 8765 to 8774 and writes the chosen one to the `connection.json` file. The bridge finds it on its own. If 8765 is taken, for example by AnkiConnect, the server picks another.
Discussion
No questions or reviews yet.
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Comparison with similar tools
Cards that share the main search query, and how they differ.
| Tool | Official | Authentication | Repository stars | Main difference |
|---|---|---|---|---|
| Thunderbird MCP (this card) | no | API key | 443 | |
| Yandex Mail MCP server | no | API key | 0 | Yandex work mail over IMAP: reading, thread search and drafts, without a client, calendar or filters |
| outlook-mcp | no | OAuth | 455 | mail, calendar and OneDrive files through the Microsoft cloud service |
README in short
The description starts with the reason: Thunderbird has no official API for AI tools. A bridge diagram follows, then tables of all tools by group with details of their limits and sections on access control and security. Install takes two steps, and troubleshooting tips, the project structure and known issues close it.