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Miramar Alpha 3
Release Notes

Released: March 15, 2011

Miramar Alpha 3 is a preview release for the next major version of Thunderbird that is being built on top of the next generation of Mozilla's layout engine, Gecko 2.0. Miramar Alpha 3 is being made available for testing purposes only and is intended for developers and our testing community.

This release does not represent the final product. Some of the features listed below are highly experimental and will likely change before the final release. They may come with crashes and bugs and may potentially cause data loss in profiles (configuration data, preferences, downloaded mail).

Please do not use Miramar Alpha 3 in a production environment.

Please see below for a list of features and enhancements found in Miramar Alpha 3, as well as known issues and frequently asked questions. Your feedback is essential to the project and makes Thunderbird better with every alpha release. Give us your feedback on Miramar Alpha 3 at our GetSatisfaction site. Alternately, if you have specific problems, you can file a bug in Bugzilla.

What's New in Miramar Alpha 3

Miramar Alpha 3 is built on top of the Gecko 2.0 platform. The main goals of this release is to find out about possible problems caused by the changes in the underlying platform.

Notable changes in Miramar Alpha 3 from Miramar Alpha 2

  • Tabs can now be reordered and dragged to different windows
  • Revised account creation wizard, offering improved set-up
  • Plugins can now be loaded in RSS feeds by default
  • and numerous other bug fixes

Notable changes in Miramar Alpha 3 when compared to Thunderbird 3.1

  • New Addons Manager and extension management API (user interface will be changed before final release)
  • Attachment sizes now displayed along with attachments
  • New troubleshooting information page to aid supporting and diagnosing problems in Thunderbird
  • Several user interface fixes for Windows Vista/Windows 7
  • Support for Mac 32/64 bit Universal builds (Miramar Alpha 3 will no longer support PowerPC on Mac)
  • Over 390 platform fixes to improve performance and stability

For a more detailed list of bug fixes, see the the full bug list.

System Requirements

Before installing, make sure your computer meets the system requirements.

Downloading Miramar Alpha 3

Mozilla Messaging provides Miramar Alpha 3 for Windows, Linux, and Mac OS X in the English language. You can get the latest alpha version of Miramar here.

Installing Miramar Alpha 3

Please note that installing Miramar Alpha 3 may overwrite your existing installation of Thunderbird on Linux. Windows and Mac OS X will install to different locations, however it is recommended that you check the messages during installation. For all systems, you won't lose any of your messages or address books, but some of your extensions and other add-ons might not work until updates for them are made available.

Users are highly encouraged to install Miramar Alpha 3 in another folder (on Windows, this is done using Custom Install) and backup their profiles before testing Miramar Alpha 3.

Uninstalling Miramar Alpha 3

You can remove Miramar Alpha 3 through the Control Panel in the Start Menu on Windows, by removing the Miramar application on OS X, or by removing the thunderbird folder on Linux.

Removing Miramar Alpha 3 won't remove your emails or newsgroup messages. This data is stored in your profile folder, which is located in one of the following locations depending on your operating system:

Windows Vista Users\<UserName>\AppData\Roaming\Thunderbird
Windows 2000, XP, Server 2003 Documents and Settings\<UserName>\Application Data\Thunderbird
Mac OS X ~/Library/Thunderbird
Linux and Unix systems ~/.thunderbird

Any version of Thunderbird that you install after removing Miramar Alpha 3 will continue to use the data from this profile folder.

Extensions and Themes

Extensions installed under previous versions of Thunderbird may be incompatible and/or require updates to work with Miramar Alpha 3. Please report any issues to the maintainer of the extension.

When you install Miramar Alpha 3 all of your Extensions and Themes will be disabled until Miramar Alpha 3 determines that either a) they are compatible with the Miramar Alpha 3 release or b) there are newer versions available that are compatible.

Known Issues

This list covers some of the known problems with Miramar Alpha 3. Please read this before reporting any new bugs.

All Systems
  • If you are unable to view content for your RSS feeds in the Wide View Layout, you may need to disable the Lightning Calendar add-on if you have it installed or switch to Classic View and restart Thunderbird. (Bug 531397)
  • In some cases, using 'Save As Template' from the File menu may not work. You can still Save As Template from the email Compose window or drag the message into the Template folder. (Bug 532050)
Mac OS X
  • Import of Eudora mail has been disabled for this release if running in 64-bit mode (Mac OS X 10.6). Work is ongoing to restore this in future alphas (Bug 537872).


  • Poorly designed or incompatible extensions can cause problems with your email client, including make it crash, slow down message display, etc. If you encounter strange problems relating to parts of the email client no longer working, the email client not starting, windows with strange or distorted appearance, degraded performance, etc, you may be suffering from Extension or Theme trouble.
    Restart the email client in Safe Mode. On Windows, start using the "Safe Mode" shortcut created in your Start menu or by running thunderbird.exe -safe-mode. On Linux, start with ./thunderbird -safe-mode and on Mac OS X, run:

    cd /Applications/
    ./thunderbird-bin -safe-mode

    When started in Safe Mode all extensions are disabled and the Default theme is used. Disable the Extension/Theme that is causing trouble and then start normally.
  • If you encounter strange problems relating to email, feeds or newsgroup messages, it is recommended that you try creating a new profile and attempting to reproduce the problem before filing bugs. Create a new profile by running Thunderbird with the -P command line argument, choose the "Manage Profiles" button and then choose "Create Profile...". Migrate your settings files (Emails, feeds, etc) over one by one, checking each time to see if the problems resurface. If you do find a particular profile data file is causing a problem, file a bug and attach the file, being sure to remove any private information as necessary.

Frequently Asked Questions

  1. What can I do to help?

    Your feedback is essential to the project and makes Thunderbird better with every alpha release. Give us your feedback on Miramar Alpha 3 at our GetSatisfaction site. Please read these notes and the bug filing instructions before reporting any bugs to Bugzilla.

  2. Where can I discuss Miramar Alpha 3 features or issues?

    If you want to join the conversations about new features or need troubleshooting advice, visit Mozilla Messaging at Get Satisfaction. You can also post questions in the "" newsgroup, available on Mozilla's news server, or via the web, using Google Groups. It is also available as a mailing list. Please read the Mozilla Forum Etiquette page before posting.

  3. Where can I get extensions and themes (add-ons)?

    Extensions and Themes can be downloaded from Thunderbird Add-ons.

  4. Who makes Miramar Alpha 3?

    Many people! Mozilla Messaging is the organization that produces it, but it is the result of collaboration between hundreds of people around the world.

  5. Where's the Miramar Alpha 3 source code?

    A tarball of the Miramar Alpha 3 source code is available for download. The latest development code can be obtained by Mercurial. For more details on the layout of the source, see the comm-central information page. Please follow the build instructions.