Stop ubuntu updating thunderbird
To help keep things stable, they will frequently disable Help - Check for Updates, forcing you to wait for the next release of the Linux distribution for any new functionality.
It can be used with any Linux distribution or window manager, but is somewhat Ubuntu-centric due to that distribution's popularity.
Press the Search button and enter firefox (or thunderbird).
Scroll through the list and find the firefox package.
You could also just type the following from the root in a console: The easiest way to install Mozilla applications is through Ya ST, the SUSE/open SUSE package manager (you have other options with the 10.2 versions).
Those RPM software packages are customized versions of the regular releases.
Use either the Synaptic (Gnome) or Adept (KDE) package manager to install the application depending upon which type of Ubuntu you're running.