Copy Message ID and Subject

This extension adds a button to the message view toolbar that copies either the Subject or the Message-ID of the displayed message to the clipboard. Copying the Message-ID is useful when referencing an email from the command line (e.g. git send-email --in-reply-to); copying the Subject is handy for bug tracker entries, chat references, and notes.

The toolbar button opens a small menu with two entries:

• Copy Message ID
• Copy Subject

Two keyboard shortcuts are provided for one-keystroke access (configurable in the add-on's options page):

• Ctrl+Alt+O — copy Message-ID
• Ctrl+Shift+O — copy Subject

Installation

Get it from the Mozilla add-ons platform

Located here

Install it manually

1. Checkout this repo
2. Run make to generate the xpi file.
3. In Thunderbird, go to the Add-ons Manager.
4. Click Install Add-on From File... and select the xpi file from step 2.

Options

Open the add-on's options page to configure:

• Prefix / Suffix — wrapped around the copied value (applies to both Message-ID and Subject).
• Include angle brackets — keep the <> around the Message-ID (Message-ID only).
• URL encode — percent-encode the copied value.
• Raw Message-ID header — copy the verbatim Message-ID: header line(s) from the raw message source (Message-ID only).
• Compact button — show icon only, no text label.
• Keyboard shortcuts — re-bind or reset both shortcuts.

Development

Dependencies

The build requires GNU Make and Node.js, plus a zip tool.

Windows

• GNU Make — install via Chocolatey: choco install make or download from GnuWin32
• Node.js — download from nodejs.org
• 7-Zip — download from 7-zip.org. The build script finds it automatically in Program Files without needing it on your PATH.

Linux

• GNU Make — sudo apt install make / sudo dnf install make
• Node.js — sudo apt install nodejs / sudo dnf install nodejs
• zip — sudo apt install zip / sudo dnf install zip

Building

make        # builds copy-message-id@j.kahn.xpi
make clean  # removes built xpi files

Testing locally

make test-install builds the XPI, installs it into a dedicated thunderbird-test profile, populates an inbox with the emails from tests/, and launches Thunderbird automatically:

make test-install

Thunderbird will open with a fresh profile containing all the test messages. Open any message and click the toolbar button to choose Copy Message ID or Copy Subject from the menu (or press Ctrl+Alt+O / Ctrl+Shift+O to copy directly without opening the menu).

A small badge (✓ green / ✗ red) flashes on the toolbar button for ~1.5s to confirm the result of the copy.

Re-running make test-install reinstalls the latest build into the same profile — no need to restart or toggle the addon.