The latest version of Thunderbird can be downloaded from Softpedia
Mozilla officially released Thunderbird 17.0.7, an email and RSS client, featuring just a few security fixes.This is just a minor update for Mozilla Thunderbird, as it can be easily seen from the complete lack of changes that usually accompany any release.
Users were hoping to get a new Thunderbird, maybe a stable version in the 18.x branch, but the Mozilla developers didn't grace us with a new major release.
If you want to get this version of Mozilla Thunderbird in Ubuntu, you're going to have to wait until it hits the official repositories.
Mozilla provides binaries that don't have to be installed in order to work, and those packages are available from the links posted below.
Check out the official release notes for a complete list of changes and updates.
Download Mozilla Thunderbird 17.0.7 for Linux.
Download Mozilla Thunderbird 17.0.7 for Windows.
Download Mozilla Thunderbird 17.0.7 for Mac OS.