On October 10th, 2012, Mozilla released Thunderbird 16. New in this release:

• Added box.com to the list of online storage services that are available for use with Thunderbird Filelink
• Silent, background updates
• Various updates and secuirty fixes

Existing Thunderbird users should be offered the update shortly or can do so manually either by going to Help > About Thunderbird and following the prompts or downloading and installing Thunderbird 16 via the getthunderbird.com site.

Lighting Users: Since Lightning add-on is tied to each specific version of Thunderbird, you will be prompted to update Lightning when Thunderbird restarts after the update.

Thunderbird 10.08esr was also released today. The next releases will be on/around November 20th and will be Thunderbird 17 and 17.0esr.