# Mail Front-End In January 2023 the mail front-end was rebuilt from scratch, replacing what evolved from the original Netscape front-end. This is a developers' guide to the new UI. ## Mail tab types The mail front-end consists of two types of tabs (and a standalone window, more about that later) – the 3-pane tab `mail3PaneTab` and the message tab `mailMessageTab`. These are defined in [mailTabs.js](https://searchfox.org/comm-central/source/mail/base/content/mailTabs.js) and provide the `tabInfo` objects for tabmail to control. Most code from outside the tabs will go through here in some form, although knowing the specific details should be unnecessary. Each mail tab `tabInfo` object has these read-only properties: * `chromeBrowser` – This is a XUL `` object which displays the tab's contents, either `about:3pane` or `about:message`. As with any `` object you can access the displayed page with the `contentWindow` and `contentDocument` properties. * `browser` and `linkedBrowser` – Both refer to the XUL `` currently displaying content (an email message or a web page) to the user, or `null` if there isn't any. * `message` – The currently displayed message as an `nsIMsgDBHdr`, if there is one. * `folder` – The folder containing the currently displayed message, an `nsIMsgFolder`. ## Accessing tabs If the mail tab you're interested in is the current tab, the following properties of tabmail point to it: * `currentTabInfo` – The `tabInfo` object described above. * `currentAbout3Pane` – The `window` object of the page displayed in the `chromeBrowser`, if the current tab is a 3-pane tab. * `currentAboutMessage` – The `window` object of the message display page, which for message tabs is the page displayed in the `chromeBrowser`, and for 3-pane tabs a page within that. If it's not the current tab, you can get the `tabInfo` object from tabmail and use the properties listed in the previous section to access it. ## Mail windows The standalone mail window also contains a XUL `` displaying `about:message`. The browser can be accessed from the window's `messageBrowser` property. ## about:3pane `about:3pane` is the main UI that users see when Thunderbird starts: the folder pane, the thread pane, and the message pane. It lives in the tree as [about3Pane.xhtml](https://searchfox.org/comm-central/source/mail/base/content/about3Pane.xhtml) and similarly named [JS](https://searchfox.org/comm-central/source/mail/base/content/about3Pane.js), [CSS](https://searchfox.org/comm-central/source/mail/themes/shared/mail/about3Pane.css) and [Fluent](https://searchfox.org/comm-central/source/mail/locales/en-US/messenger/about3Pane.ftl) files. ### Folder pane The folder pane displays the accounts and folders within them. Various modes of display are available. ### Thread pane The thread pane displays the list of messages in the current folder, and the Quick Filter bar for filtering those messages. ### Message pane This mesage pane contains more XUL ``s for displaying various things: * `webBrowser` – displays web content in a child process as Firefox does. * `multiMessageBrowser` – displays messages if more than one is selected. * `messageBrowser` – displays a single message using `about:message`. Only one is visible at any given time. ### Account central If an account is selected in the folder pane instead of a folder, yet another ``, `accountCentralBrowser` – displays Account Central, a page of various things you can do in Thunderbird. ## about:message `about:message` is all of the UI that displays a single message, including the message headers and attachments. It is used as the message pane in `about:3pane` and by itself as a message tab or window. Like `about:3pane` it lives in the tree as [aboutMessage.xhtml](https://searchfox.org/comm-central/source/mail/base/content/aboutMessage.xhtml), [aboutMessage.js](https://searchfox.org/comm-central/source/mail/base/content/aboutMessage.js), [messageHeader.css](https://searchfox.org/comm-central/source/mail/themes/shared/mail/messageHeader.css) and [about3Pane.ftl](https://searchfox.org/comm-central/source/mail/locales/en-US/messenger/about3Pane.ftl) files. Message contents themselves are displayed in a `` (if you're counting, we're now three deep) which can be accessed by the `content` property of an `about:message` `window`. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://developer.thunderbird.net/thunderbird-development/codebase-overview/mail-front-end.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.