v1.0.0

Thunderdown v1.0.0

Thunderbird extension that turns Markdown into email-ready HTML. Write in Markdown, click the button, and the compose body becomes styled HTML with all CSS inlined. No <style> blocks means Gmail, Outlook, Apple Mail, and other clients won't strip your formatting.

When replying to an email, Thunderdown only renders your new text — the quoted original stays untouched.

Features

• GFM Markdown: headings, lists, tables, task lists, blockquotes, links, images
• Syntax-highlighted code blocks (JavaScript, Python, Go, Bash, SQL, JSON, YAML, XML)
• All CSS inlined for email client compatibility
• Toggle between Markdown source and rendered HTML with toolbar button or keyboard shortcut
• Quoted replies preserved when composing replies
• Auto-updates from GitHub Releases (Thunderbird checks every 24 hours)

Requirements

• Thunderbird 128.0 or later

Install

1. Download thunderdown-1.0.0.xpi from the Assets section below
2. In Thunderbird, open the Add-ons Manager (Ctrl+Shift+A / Cmd+Shift+A on Mac)
3. Click the gear icon, then Install Add-on From File...
4. Select the downloaded .xpi file

How to use

1. Open a compose window (new email or reply)
2. Write your email in Markdown
3. Click the Thunderdown button in the toolbar, or press Ctrl+Shift+M (Cmd+Shift+M on Mac)
4. Your Markdown is replaced with styled HTML — send it
5. Click the button again to toggle back to the raw Markdown if you need to edit

Upgrades

After installing this version, Thunderbird will automatically check for new releases every 24 hours. When a new version is available, Thunderbird will prompt you to update — no manual download needed.