MailChat for Thunderbird

Connect Thunderbird to local Codex chats on your Windows PC. Search and read messages, download selected attachments, and prepare new drafts and replies with your account signature and RFC-linked conversation history.

NEW IN 1.4.1: Edit existing open drafts from Codex while retaining attachments, signature and conversation history. Closed drafts must first be opened manually in Thunderbird. This feature requires both the 1.4.1 extension and Windows bridge; the beta package is available from the release link below. Edited drafts are sent manually.

Drafts only is the default: the chat cannot send mail. You review and send personally in Thunderbird. Optional autonomous sending must be explicitly enabled in both the Windows installer and extension settings, with the optional Thunderbird send permission. In that mode, the chat can send without another human review. Creating a draft never sends automatically.

REQUIREMENTS: Windows, Thunderbird 153 or later, Node.js 22 or later, and Codex desktop with local MCP support. Installing this add-on alone is not sufficient: download the Windows bridge from https://github.com/andrea199/mailchat-for-thunderbird/releases/tag/v1.4.1-beta.1 , extract the ZIP and run Install.cmd. Each user receives their own local pairing key. Leave Thunderbird open while working from Codex.

PRIVACY: The bridge uses authenticated localhost communication. This project runs no hosted mail-processing service and collects no telemetry. Mail and attachments requested through Codex may be processed by its AI provider. Read the privacy notice and accept the data-sharing notice before pairing.

BETA: Version 1.4.1 passed all 16 automated mock, HTTP and installer tests. Clean-profile Thunderbird/Codex end-to-end testing remains outstanding. Use a test account for initial evaluation.

Independent community project, not an official Thunderbird or OpenAI product. MIT license. The bridge and add-on are free; your AI service may require its own account or subscription.

Installation, source code and support: https://github.com/andrea199/mailchat-for-thunderbird

First public beta of MailChat for Thunderbird.

Default drafts-only mode blocks sending from the chat. Optional autonomous sending requires explicit activation in both the Windows installer and Thunderbird settings, plus compose.send permission.

Search and read local mail, download selected attachments, prepare new drafts and native replies with account signature and RFC-linked predecessor history. Missing history fails explicitly. Exact draft content and permissions are checked before autonomous sending; uncertain sends are not retried automatically.

Requirements: Windows, Thunderbird 153+, Node.js 22+ and Codex desktop with local MCP support. Download the required Windows bridge and installation instructions from https://github.com/andrea199/mailchat-for-thunderbird/releases/tag/v1.4.0-beta.1 . The XPI alone is not sufficient.

Nine automated mock/HTTP/installer tests passed. Real Thunderbird/Codex end-to-end testing remains outstanding. Beta release, independent project, MIT license.

# MailChat privacy notice

MailChat is an independent, open-source local bridge between Thunderbird and Codex on the same computer. The project author operates no MailChat mail-processing server and collects no telemetry through this extension.

## Data and where it goes

The extension accesses account identities, message metadata, selected message bodies and attachments to answer tool requests. Reply preparation retrieves the original and RFC-linked predecessors. These data are sent over authenticated localhost HTTP to the local Node.js bridge. Tool responses are then returned to Codex. Codex and its connected AI provider may transmit, store or process those data under their own terms and privacy settings. Check those settings before using MailChat with confidential or other people's mail.

Outgoing local files are read only from supplied paths, verified by SHA-256 and transferred through the bridge for attachment to drafts. Selected received attachments are saved under the installation's private local attachment directory. The chat can subsequently read those local files with its own tools. Mail sent or drafts saved are also processed by your configured mail provider.

The extension stores a local pairing key, mode and consent choice in Thunderbird storage, together with draft verification records and sending receipts. The Windows installer stores two random authentication keys, mode and port in `connection.json` and prints the extension key in `Pairing-Key.txt`. Keep the installed folder private and out of shared/cloud folders. MailChat does not bundle your passwords or an AI API key.

## Consent and sending

No email tools are handled until you pair the extension and accept its data-sharing notice. Drafts-only is the default. Sending is optional and requires autonomous mode in both the installer and extension, plus the Thunderbird `compose.send` permission. In autonomous mode the AI can send without an additional approval of each draft. Content in mail is treated as untrusted data in tool instructions, but AI behaviour is not a privacy or correctness guarantee.

## Control and retention

Disable automatic sending in extension settings, or disconnect to remove the pairing key and consent. Disconnecting does not erase already-created drafts, chat history, locally downloaded files or verification records. Removing the extension removes its local extension storage according to Thunderbird behaviour; remove the installation folder to delete bridge keys and downloaded attachments. You control mail and chat retention separately with your providers.

No tracking, advertising or analytics libraries are bundled. This notice describes the project code, not the independent practices of Thunderbird, your mail provider or your AI service. For questions, use the project's GitHub Issues, without posting private mail or keys.

Some add-ons ask for permission to perform certain functions (example: a tab management add-on will ask permission to access your browser’s tab system).

Since you’re in control of your Thunderbird, the choice to grant or deny these requests is yours. Accepting permissions does not inherently compromise your browser’s performance or security, but in some rare cases risk may be involved.

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MailChat for Thunderbird 1.4.0

by Andrea Detry

About this Add-on

Version Information

Version 1.4.0 Released Oct. 6, 2026 69.0 KiB Works with Thunderbird 153.0 and later

Add-ons

Welcome to Thunderbird Add-ons.

On the go?

MailChat for Thunderbird 1.4.0

by Andrea Detry

About this Add-on

Version Information

Version 1.4.0 Released Oct. 6, 2026 69.0 KiB Works with Thunderbird 153.0 and later

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