In addition to the feature set found in Mozilla Mail, Mozilla Thunderbird has several new features and improvements to make your mail and new experience better. Highlights include:

- The ability to customize your toolbars the way you want them. Choose View / Toolbars / Customize inside any window.
- UI extensions can be added to Mozilla Thunderbird to customize your experience with specific features and enhancements that you need. Support for extensions.
- Extensions allow you to add features particular to your needs such as offline mail support. A full list of available extensions can be found here.
- A new look and feel. Thunderbird also supports a large number of downloadable themes which alter the appearance of the client.
- An addressing sidebar for mail compose which makes it easy and convenient to add address book contacts to emails.
- Online help includes a FAQ, tips and tricks and other useful information.
- Simplified preferences UI and menus.
- Footprint and performance improvements.

First-timers: There are no official installers for this release. The installation instructions below assume you will download the program files in a single, compressed file, which must be manually extracted to your hard disk.

Download:
Mozilla Thunderbird 1.5 RC2