For bugs in MZLA's Thunderbird desktop mail client. Bugs in the back-end (e.g. protocols) should be filed in the MailNews Core product. Bugs in calendar should be filed in the Calendar product. Bugs for the chat features, file in the Chat Core product.

Select a component to see open bugs in that component:

Account Manager

Problems with setting up multiple mail and news accounts within a single profile in Mozilla Thunderbird.

Add-Ons: Extensions API

APIs to enable WebExtensions and legacy extensions

Add-Ons: General

Manage installation and update of extensions, themes and dictionaries within Add-ons Manager

Address Book

Problems with using the Thunderbird Address Book such as creating new cards, manipulating the data from the Address Book.

Build Config

For bugs that result from Mozilla build problems. ("Building" is the process of converting the thousands of Mozilla source code files into a actual executable software.) If a file in a newly-downloaded build is missing or corrupted, file the bug in this component.

Examples of appropriate bugs: DLL files are missing from the ZIP file; Build contains a zero K executable.

Disability Access

Accessibility compliance bugs in Thunderbird: screen readers, magnifier tools support, user interface bugs affecting on disabled people experience.


Problems with using Tools | Filters, Spam or Junk processing (aka bayesian filtering). For example: 1. Problems with creating, editing, deleting, using filters. 2. Incoming mail is not filtered properly.

Folder and Message Lists

The list of folders and/or the list of messages in the 3-pane window.


A "catch all" component for problems found when using the Thunderbird e-mail client which do not fall into one of the current components. Example: launch/exit crashes, features missing, etc. PLEASE NOTE!! Try to find a component which is specific to your bug first - BEFORE assigning to this component!

Help Documentation

Inaccurate information and typos in Thunderbird's help documentation.


Bugs and feature requests for the Thunderbird application install wizard.

Instant Messaging

Issues related to Instant Messaging : Facebook, xmpp, irc, chat, etc.


Thunderbird localization bugs - Langpacks, localized build, supported languages

Mail Window Front End

Problems with main mail window, standalone message window, sidebar contents, toolbars, dialogs, etc. A few examples: 1. User interface and functionality problems within the 3-pane mail window and the standalone message window.

Message Compose Window

Problems with the writing a new email or replying to one including using the autocomplete feature.

Message Reader UI

The area that displays the header and body of the message, either in the 3-pane window or the standalone message window.


For bugs related to the new migration code for auto migration from other mail clients to Thunderbird.

OS Integration

Areas where Thunderbird integrates with the host desktop environment. Please use the relevant UI component for any Theme-related issues. Please use the "Core" product for other OS integration problems.


Bugs and feature requests for Thunderbird preferences. This includes the preferences manager as well as the preferences defaults.


For app-level security bugs.

If the problem relates to underlying components (PSM, NSS, Core, Toolkit) then please file it in the appropriate product instead of here.

Testing Infrastructure

Bugs relating to the testing infrastructure that is specific to Thunderbird, e.g. Mozmill.


Bugs and requests for enhancements or changes to the default theme that ships with Thunderbird (use the OS target to indicate Windows, Mac, or Linux theme).

Toolbars and Tabs

Toolbars and tabs in either the 3-pane window or the standalone message window.


For newly filed bugs that need some help.

Upstream Synchronization

Bugs about keeping comm-central in sync with mozilla-central. File bugs here to alert the Thunderbird developers to changes they will need to make.