Thunderbird Slack Provider

A Thunderbird WebExtension that lets you read and write Slack messages without leaving your email client.

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Features

Feature	Details
Channel list	All Slack channels you are a member of appear in the left panel.
Unread badges	Channels with unread messages are shown in bold (Thunderbird style).
Message thread	Click a channel to see its messages in the right panel, newest at the bottom.
Compose & send	Type in the box at the bottom; press Enter to send (Shift+Enter for a new line).
Reply in thread	Every message has a Reply button. Replies are sent as Slack threads and are also broadcast to the channel.
Live updates	The extension polls Slack every 30 seconds to refresh messages and unread counts.

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Building on Linux

Prerequisites

Tool	Version	Install
zip	any	sudo apt install zip
python3	≥ 3.6	sudo apt install python3
git	any	sudo apt install git

No Node.js or Rust toolchain is required. The extension is pure JavaScript / HTML / CSS.

Minimum Thunderbird version: 128.0 (the Supernova UI rework and the stable Spaces API both require Thunderbird 128+).

Steps

# Clone the repository
git clone https://github.com/gortazar/thunderbird-slack-provider.git
cd thunderbird-slack-provider

# Extract the version number from the manifest
VERSION=$(python3 -c "import json; print(json.load(open('src/manifest.json'))['version'])")

# Package all source files into an .xpi file (a renamed .zip)
mkdir -p dist
cd src
zip -r "../dist/thunderbird-slack-provider-${VERSION}.xpi" .
cd ..

echo "Built: dist/thunderbird-slack-provider-${VERSION}.xpi"

The resulting .xpi file contains everything needed for installation.

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Allowing the Extension to Access Your Slack Workspace

The extension uses the Slack Web API with a Bot or User OAuth token.

1 — Create a Slack App

1. Go to https://api.slack.com/apps and click Create New App → From scratch.
2. Give it a name (e.g. Thunderbird Slack Provider) and choose your workspace.

2 — Grant the Required Scopes

Navigate to OAuth & Permissions → Scopes.

Add the following Bot Token Scopes:

Scope	Purpose
channels:read	List public channels
groups:read	List private channels
channels:history	Read public channel messages
groups:history	Read private channel messages
chat:write	Post messages
users:read	Resolve display names and avatars
channels:manage (optional)	Mark channels as read

3 — Install the App to Your Workspace

1. Click Install to Workspace on the OAuth & Permissions page.
2. Authorise the permissions.
3. Copy the Bot User OAuth Token (starts with xoxb-).

4 — Enter the Token in Thunderbird

1. Open Thunderbird and navigate to the Slack space (Slack icon in the left toolbar).
2. If not yet configured, click Open Settings.
   Alternatively: Tools → Add-ons and Themes → Thunderbird Slack Provider → Preferences.
3. Paste your token and click Save Token.
4. Click Test Connection to verify everything works.

Tip – User Token vs Bot Token
A Bot Token (xoxb-) only sees channels the bot has been invited to.
A User Token (xoxp-) sees all channels the human user can access.
For personal use, a User Token with the same scopes is often more convenient.

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Installing the Extension

Option A — Install from the pre-built release

1. Download the latest .xpi from the Releases page.
2. Follow Option B → Step 3 below.

Option B — Install a locally-built .xpi

Standard (non-snap) Thunderbird

# Open Thunderbird
thunderbird &

1. In Thunderbird open Tools → Add-ons and Themes (or press Ctrl+Shift+A).
2. Click the ⚙️ gear icon → Install Add-on From File….
3. Browse to dist/thunderbird-slack-provider-<version>.xpi and click Open.
4. Click Add on the confirmation dialog.
5. The Slack icon will appear in the Spaces toolbar on the left side of the Thunderbird window.

Snap-installed Thunderbird

Snap packages use strict confinement and mount the application in a read-only filesystem.
Install the add-on through the Thunderbird UI in exactly the same way:

# Launch the snap version
snap run thunderbird &

Then follow steps 1–5 from the standard installation above.
The Add-on Manager is identical regardless of how Thunderbird was installed.

Note: Thunderbird requires add-ons to be signed by Mozilla for automatic installation in release builds.
To install an unsigned add-on locally:

1. Go to about:config in a Thunderbird compose window (or open it via the URL bar in a tab).
2. Set xpinstall.signatures.required to false.
3. Restart Thunderbird.

Alternatively, use the Developer Edition of Thunderbird, which has signature enforcement disabled by default.

Option C — Persistent installation (developer mode)

For development and testing without repackaging after every change:

1. Navigate to about:debugging in Thunderbird.
2. Click This Thunderbird.
3. Click Load Temporary Add-on….
4. Select src/manifest.json from the cloned repository.

The extension will be active until Thunderbird restarts.

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CI / CD

Every pull request and push to main triggers the Build and Release workflow (.github/workflows/build.yml):

1. Validate – checks that manifest.json is well-formed and contains all required fields.
2. Package – zips the src/ directory into a .xpi file.
3. Upload artifact – attaches the .xpi to the workflow run for inspection.
4. Publish release (main branch only) – creates (or replaces) a GitHub Release tagged v<version> with the .xpi as the downloadable binary.

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Contributing

Pull requests are welcome. To run the development version, see Option C above.

Please keep the version field in src/manifest.json updated for any release you intend to ship — the CI pipeline derives the release tag from it.

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License

Apache-2.0