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Thunderbird 2 Roadmap

Scott MacGregor (11/06/2006)


Our goal is to continue to build a "best of breed" email product for Windows, Linux and Mac OS X by focusing on: privacy, spam, security, and tools for organizing and managing your e-mail. We have ambitious goals for the workload between now and our next major release. This document is a description of our current thinking on how we intend to get to Thunderbird 2.


Feature planning and discussion is done on the Mozilla Wiki. See the Thunderbird 2 Product Planning document for more information.

Here are the top level themes for the Thunderbird 2 release:

  • Tools for organizing and managing e-mail
    • Custom Folder Pane Views such as favorites, unread and recently used.
    • Message Tagging
    • Tabbed Messages
  • Be Informative
    • New Mail Alert Improvements
    • Folder Summary Popups
  • Help Fight Junk Mail
    • Improve the current bayesian based algorithm
    • Token Store Pruning / Aging

Please talk to the module owners if you are interested in getting involved. In particular, we are looking for developers with strong math backgrounds to help improve the bayesian spam filter.

Branch Plan and Management

Thunderbird 2

Thunderbird 2 will be based on continued development of the Gecko 1.8 branch created for Firefox and Thunderbird 1.5. Care must be taken by developers to ensure their work reaches both the branch and the trunk, to avoid aviary-branch style inconsistencies. Thunderbird 2 specific feature work requires module owner approval before landing on the 1.8 branch.

Thunderbird 1.5.x

We plan on offering several stability updates to Thunderbird 1.5 during 2006. These stability updates will be based on the Mozilla 1.8.0 branch and will leverage the new software update system. Changes on this branch will be limited to security issues, top crash fixes and a handful of serious regression fixes.

Thunderbird 3

Thunderbird 3 will offer additional user interface enhancements and many substantial platform improvements. It will be based on Gecko 1.9 (the current Mozilla trunk). We are currently brainstorming about various user interface improvements to take advantage of the advanced graphic rendering work being done for Gecko 1.9. Most Thunderbird 2 feature work lands on the trunk first and then onto the 1.8 branch.

Milestone Plan

This is, as always, subject to change.

Milestone Release Date Summary
1.0 2004-12-06 Inaugural Release
1.5 2006-01-11 software update, spell check as you type, phishing detector, podcasting.
2a End of July 2006 pre-feature complete alpha
tb2 beta 1 Early December 2006 feature complete beta (en-US string freeze)
tb2 beta 2 Week of January 24th
Freeze for RC 1 March 6th Final Code and l10n string freeze
3.0 Q1 2008?

Dates are subject to change.

Pre-Release Builds

Alpha releases are testing milestones and do not represent what we intend to ship as final. They may contain missing features, numerous bugs, etc. They are intended for our developer and testing community to work with to build upon and provide us with early feedback in the event major changes need to happen before the final release.

Beta releases are feature-complete and represent a rough idea of what we'd like to ship. These are for a more general early-adopter/testing audience that wants to see what the next release of Thunderbird is going to look like so that they can provide us with feedback on the most important issues to fix before the final release.

Release Candidates are facsimiles of what we intend to ship under any of the above categories or the final release itself. We usually post these a few days or weeks ahead of the release in question, to see if there are any critical bugs present that must be fixed. If there are none, we ship the release candidate as "final".

Please Note! Alpha releases are not for general consumption and may crash, delete your profile, your hard disk, etc. They are very little more than a blessed Nightly Build. Preview Release builds may also suffer bugs and should be downloaded only by people willing to test pre-release software.

Release Dates

Dates shown above are tentative and serve only to give you an idea of the relative position of one release from another. They represent our current state of thinking as to the release dates at the time this document was last updated, and may have changed since then.


As with 1.x, all releases moving forward will be available in as many languages as can be made ready at the time of release. Localizers and others dependent on release timing should use this document as an indicator of the up-to-date release time.


With client products now among the most important delivery vehicles for Gecko technology, we will be building up an aggressive campaign to market Thunderbird. The why document was a successful start to our marketing efforts. Other initiatives include a new product site, a promotional button and signature campaign. We would also like to better leverage the spreadfirefox marketing effort.

Support Network

Thunderbird has a tremendous community following, and we wish to highlight the following two sites - Thunderbird Help for a wide selection of helpful information; and the MozillaZine Forums - our premier discussion site for users and developers.

Past Roadmaps