Documentation

Installation, first steps, every setting and what to do when something goes wrong. Glassbird first, then Glassbird Pro.

Install

Glassbird is an add-on for Thunderbird 153 to 161 and Betterbird. It needs no terminal and no restart.

  1. In Thunderbird, open Tools › Add-ons and Themes.
  2. Search for “Glassbird” and choose Add to Thunderbird. If you downloaded the file glassbird-<version>.xpi, use Install Add-on From File… in the gear menu.
  3. Thunderbird asks for full access. Glassbird needs it because it styles Thunderbird's own windows. It does not read your mail and sends nothing over the network.

If you prefer the terminal, every release has an install script: install.sh for macOS and Linux, install.ps1 for Windows. It backs up your existing chrome folder before it changes anything. Add-on and script exclude each other: if both are there, the add-on stays idle and says so.

First steps

Right after installing, the setup assistant opens.

Every choice applies at once; only new symbols need a restart of Thunderbird. When an update brings a new question, the assistant asks only that one. You can open it again at any time from Glassbird's settings.

Settings

You find the settings under Add-ons and Themes › Glassbird › Options.

Remove

In Add-ons and Themes, choose Remove for Glassbird. Glassbird then clears its folder in your profile and its settings. This only works while it is enabled: a disabled add-on cannot clean up after itself.

If something looks wrong after a Thunderbird update, Help › Troubleshoot Mode helps. Thunderbird then starts without add-ons, and you see whether Glassbird is the cause.

Glassbird Pro

Glassbird Pro is a separate add-on. It goes with Glassbird but also runs without it. Some features also need Glassbird Pro Experiments, a small companion add-on for interfaces Thunderbird does not yet offer add-ons officially. The assistant tells you where that is the case.

You can try Pro for 30 days, once per Thunderbird profile; the trial needs the companion add-on. A licence key brings twelve months of updates from purchase: new versions, adjustments to new Thunderbird versions, security and bug fixes. After that, we owe no more updates; newer versions that Thunderbird installs anyway come without any entitlement to them. Your version keeps working with the Thunderbird versions it supports. Renewing for another twelve months costs €15, paid once, no subscription. The settings of Glassbird Pro show until when your updates are included. Glassbird Pro activates the key with our activation service when you enter it and has it checked about every 30 days. A licence covers up to five Thunderbird profiles at a time, each profile counting as a device of its own; you deactivate devices under Settings › License or at glassbird.app/aktivierung. If no check succeeds for 90 days, Pro carries on as the free version, and your data stays. As a small business under § 19 UStG, we charge no VAT.

DKIM: Under Thunderbird additions › Check senders (DKIM), Pro shows in the header of every mail and in Conversations whether its signature is valid and which domain signed it. Pro looks up the key over DNS over HTTPS when the mail arrives, at Quad9, Mullvad or your own service, so no sender can tell from the lookup when you read. After you switch it on, Pro checks the latest 500 mails of each inbox once, in random order; the settings show how far it got. Where a mail says “Not checked” or “Invalid”, Check now checks it again at once; that lookup can reveal that you are reading the mail just then. Where fetching changes mail, as Proton Bridge does, Pro shows the result Proton checked on arrival, such as “Valid · signed by paypal.de, checked by Proton on arrival”. Pro believes that result only in the bridge's account and not for mail imported from Gmail. On request Pro also checks mail without a stored result, older mail for instance, when you open it; that is off by default, as the lookup can then reveal when you read.

Browser extension (beta): For Firefox, Chrome and Brave there is a small extension that passes pages to Thunderbird for later, onto the board, as a note or as an event, and types snippets into web pages. It only talks to Thunderbird on your computer.

Under Connections you link Nextcloud (sign-in in the browser, with its own app password), Obsidian, Joplin and Anytype, each with one button.

AI and My style

The writing aids work with the language model you choose: locally with Ollama or LM Studio, or at a provider with your own key, such as Mistral or Scaleway in the EU, OpenRouter, OpenAI, Google Gemini or Anthropic Claude. Glassbird Pro only shows a model as local when its address is in your own network.

Before you have a draft written, the window tells you how many mails go along as context and whether they stay on your computer.

My style teaches the model how you write: from examples of your sent mail, a style profile, seven short questions and the corrections you make to drafts. All of it is stored locally. Before a style profile or suggested rules are made at a cloud provider, Glassbird Pro asks; when writing, the chosen examples go with the draft to the model you have set up. Two included skills take care of natural wording and remove invisible characters from AI texts.

Glassbird MCP

With Pro and the Experiments, Glassbird provides an MCP server through which AI tools such as Claude Code can read your mail and folders, filters, events, tasks, boards, cards, notes and snippets. It replaces the community's MCP servers for Thunderbird. It only listens on 127.0.0.1, that is on your own computer, and requires a token.

Out of the box it may only read. Changes, such as moving and marking mail or adding folders, events, tasks and cards, need the Allow changes switch. Even then it sends no mail but only saves drafts, and it adds new filters switched off; it never changes or deletes existing filters. The browser extension gets its own key, which reaches only its own tools. The settings show ready-made configurations to copy for Claude Code, for HTTP and for mcp-remote.

Privacy

Glassbird sends no data to us. It runs entirely inside Thunderbird. Thunderbird asks our server for updates. Glassbird Pro activates your licence key with our activation service and has it checked there about every 30 days; only the licence ID, days and an identifier per device are stored. Otherwise it only connects to services you use yourself, for example your AI provider, your Nextcloud or the weather service of the dashboard. The details are in the privacy policy.

Help and compatibility

Glassbird is tested on macOS with Thunderbird 159 and the 160 beta in light and dark appearance, on Windows and Linux with Thunderbird 158. Windows and Linux work but have not been tested thoroughly. Because Thunderbird can change its internal names in updates, a Glassbird update sometimes comes a few days after a new Thunderbird version.

If something goes wrong, open Report a Problem in the settings. Glassbird prepares a mail to glassbird@dmrc.it with system details, error messages and, if you like, a screenshot. You see everything before you send it yourself.