Provides compose-only integration with Thunderbird/Betterbird mailboxes, enabling an AI assistant to save drafts, open compose windows for review/send, and list sender accounts and identities for message sending. It cannot read, search, move, tag, delete, forward, or reply to mail.
Click on "Deploy Server".
Wait a few minutes for the server to deploy. Once ready, it will show a "Started" state.
In the chat, type @ followed by the MCP server name and your instructions, e.g., "@ThunderSend MCP draft an email to sarah@example.com about tomorrow's meeting"
That's it! The server will respond to your query, and you can continue using it as needed.
Here is a step-by-step guide with screenshots.
A compose-only MCP server for Thunderbird and Betterbird. An AI assistant connected through it can do exactly two things with your mailbox:
saveDraft -- write a message to the Drafts folder.
sendMail -- open a compose window for you to review and send (or, only if you explicitly disable the safety setting, send directly).
Two helper tools exist so a client can pick a sender identity: listAccounts and getAccountAccess. That is the whole surface. There is no tool to read, search, move, tag, delete, forward or reply to mail, and no contact, calendar, folder or filter access. The code for those features was removed from the extension, not merely hidden behind a flag.
ThunderSend is a minimal fork of
TKasperczyk/thunderbird-mcp
(MIT). The compose, draft, attachment-safety and authentication code is taken
verbatim from upstream v0.9.0; see LICENSE.
MCP client (Claude, etc.) <-- stdio --> mcp-bridge.cjs <-- HTTP 127.0.0.1 --> ThunderSend extensionThe extension runs an HTTP server bound to 127.0.0.1 on port 8765 (or the next
free port). Every request needs a Bearer token that is generated randomly on
each start with the XPCOM random generator.
Port and token are written to <temp>/thundersend-mcp/connection.json with
mode 0600 and O_EXCL; the bridge reads that file. Nothing is sent anywhere else.
The bridge and the extension each enforce a hard allow-list of the four tools.
The manifest has no update_url: the add-on never fetches updates from a
third-party server. Rebuild and reinstall to upgrade.
Related MCP server: Thunderbird MCP Server
Setting | Default | Effect |
Block | on |
|
Account access | all | Restrict which accounts may be used as sender in the options page. |
Listen on all interfaces | off | Keep off unless you need LAN access and understand the token travels in clear text. |
Attachments are subject to the same deny-list as upstream: credential stores, SSH/GPG/cloud keys, browser and Thunderbird profile files, symlinks and junctions are refused on both the bridge and the extension side.
Build the XPI:
node scripts/build-xpi.cjsIn Thunderbird/Betterbird: Add-ons and Themes > gear icon > Install Add-on From File,
pick dist/thundersend-mcp.xpi, then restart.
Add the bridge to your MCP client:
{
"mcpServers": {
"thundersend": {
"command": "node",
"args": ["C:\\git-local-26-06\\thundersend-mcp\\mcp-bridge.cjs"]
}
}
}Set THUNDERBIRD_MCP_CONNECTION_FILE if the bridge cannot find connection.json
automatically.
ThunderSend uses its own add-on id, preference branch and temp directory, so it can be installed next to the full thunderbird-mcp add-on without the two interfering.
to, subject, body, cc, bcc, isHtml, from, attachments,
inReplyTo, references, replaceMessageId + replaceFolderPath, includeSignature.
All optional. Writes to the selected identity's Drafts folder and returns its URI.
to, subject, body required; cc, bcc, isHtml, from, attachments,
skipReview, includeSignature optional. With the default settings this opens a
compose window and returns immediately; the human presses Send.
Read-only lists of accounts and identities the server is allowed to send from.
npm install
npm run lint
npm test
npm run buildTests load production code by // BEGIN ... // END markers and run it in a VM
with Thunderbird services mocked, exactly as upstream does.
This server cannot be deployed
Email infrastructure for AI agents — send, receive, search, and reply to email over MCP.
Your agent needs a mailbox of its own — to receive, thread, draft and send, with attachments, without borrowing your personal inbox or your company's SMTP. **What you can ask for** • "Create an inbox for this agent and tell me its address." • "Read the new messages in this thread and draft a reply." • "Send this message with the attachment and wait for the response." • "Search this inbox for everything from that domain." • "Show delivery metrics and the events on this inbox." **How to use it** Point any MCP client at https://mcp.aisa.one/mail/mcp and sign in with OAuth — there is no key to create or paste. 49 tools: create and delete inboxes, list and read messages, raw message bodies, attachments, threads, drafts and draft attachments, send and reply, message search, inbox events, metrics, and list entries — reads and writes. **Why this rather than the source** A real inbox an agent owns, rather than an SMTP credential it borrows from a human. **It is also a door to the rest** The same login reaches 26 sources and 580+ operations. Find the contact elsewhere in the catalogue, then write to them from here — without adding a second server. **What it costs** Finding and inspecting an operation is free. Running one is billed per call at API prices, with no seat and no monthly minimum, and every call takes max_price_usd so an agent cannot overspend by accident. **Where else it reaches** https://mcp.aisa.one/sales/mcp finds the person to write to.
Hosted email MCP for your own Gmail, Outlook.com, Microsoft 365, iCloud or IMAP inbox: read, search, draft, reply in thread, forward and file mail. It moves or flags up to 500 messages in one call, and a send leaves exactly one copy in Sent. A calendar is a separate connection, and connecting one adds diary and scheduling tools.
Your own AI reads, searches and drafts in your mailbox, on your Windows computer.
