thunderbird-extension

Installation
SKILL.md

Thunderbird MailExtension Development

Complete reference for building, testing, and publishing email extensions for Mozilla Thunderbird.

Overview

Thunderbird extensions use the MailExtension API (based on WebExtensions) with the messenger.* namespace. Thunderbird supports both Manifest V2 and V3 since version 128.

Key Characteristics:

  • Global namespace: messenger (Thunderbird-specific) + browser (standard WebExtensions)
  • Both MV2 and MV3 supported (Thunderbird 128+)
  • Thunderbird-specific APIs: accounts, addressBooks, compose, folders, mailTabs, messages, messageDisplay
  • Submission via ATN (addons.thunderbird.net)

Version Requirements

Installs
8
GitHub Stars
7
First Seen
Mar 15, 2026
thunderbird-extension — codeatcode/oss-ai-skills