Mozilla has released to Beta Channel Thunderbird 8 on October 4, 2011. What’s new in Thunderbird 8 Beta includes: Add-ons installed by third party programs are now disabled by default Added a one-time add-on selection dialog to manage previously installed add-ons Improved accessibilty of the attachment lists Several user interface fixes and improvements and numerous other platform fixes Thunderbird Beta 7 users should be able to update via Help > About Thunderbird or may download and install Thunderbird 8 Beta manually here. Source: Mozilla Developer’s Center