The latest version of Thunderbird can be downloaded from Softpedia
Mozilla officially released Thunderbird 23.0 Beta 1, an email and RSS client, for all the available platforms.Mozilla said some time ago that they are not going to provide Support for Thunderbird for much longer, but they keep adding features and fixes.
Highlights of Mozilla Thunderbird 23.0 Beta 1:
• The Local Inbox folder is now allowed to grow past 4GB;
• Some redundant Makefile.in files have been removed;
• The Attachments menu has been moved under the Message menu;
• Plural forms are now supported in messenger.properties;
• Drag and drop for the RSS feed link, from the browser to the folderpane, now works properly.
Check out the official release notes for a complete list of changes and updates.
Download Mozilla Thunderbird 23.0 Beta 1 for Linux.
Download Mozilla Thunderbird 23.0 Beta 1 for Windows.
Download Mozilla Thunderbird 23.0 Beta 1 for Mac OS.
Remember that this is a beta version and it should NOT be installed on production machines. It is intended for testing purposes only.