> For the complete documentation index, see [llms.txt](https://developer.thunderbird.net/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://developer.thunderbird.net/thunderbird-development/codebase-overview/mail-front-end.md). # 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([git link](https://github.com/thunderbird/thunderbird-desktop/blob/main/mail/base/content/mailTabs.js), [searchfox link](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([git link](https://github.com/thunderbird/thunderbird-desktop/blob/main/mail/base/content/about3Pane.xhtml), [searchfox link](https://searchfox.org/comm-central/source/mail/base/content/about3Pane.xhtml)) and similarly named JS([git link](https://github.com/thunderbird/thunderbird-desktop/blob/main/mail/base/content/about3Pane.js), [searchfox link](https://searchfox.org/comm-central/source/mail/base/content/about3Pane.js)), CSS([git link](https://github.com/thunderbird/thunderbird-desktop/blob/main/mail/themes/shared/mail/about3Pane.css), [searchfox link](https://searchfox.org/comm-central/source/mail/themes/shared/mail/about3Pane.css)) and Fluent([git link](https://github.com/thunderbird/thunderbird-desktop/blob/main/mail/locales/en-US/messenger/about3Pane.ftl), [searchfox link](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([git link](https://github.com/thunderbird/thunderbird-desktop/blob/main/mail/base/content/aboutMessage.xhtml), [searchfox link](https://searchfox.org/comm-central/source/mail/base/content/aboutMessage.xhtml)), aboutMessage.js([git link](https://github.com/thunderbird/thunderbird-desktop/blob/main/mail/base/content/aboutMessage.js), [searchfox link](https://searchfox.org/comm-central/source/mail/base/content/aboutMessage.js)), messageHeader.css([git link](https://github.com/thunderbird/thunderbird-desktop/blob/main/mail/themes/shared/mail/messageHeader.css), [searchfox link](https://searchfox.org/comm-central/source/mail/themes/shared/mail/messageHeader.css)) and about3Pane.ftl([git link](https://github.com/thunderbird/thunderbird-desktop/blob/main/mail/locales/en-US/messenger/about3Pane.ftl), [searchfox link](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`.