Important: This theme will only work with Thunderbird versions 3.0 to 60.0* correctly. Moreover it supports only Windows (XP, Vista, 7, 8 and 10) at the moment. Native support for Linux and Mac OS will come perhaps.
* Check the Version History for older theme versions.
The icons are taken from the great Tango Desktop Project and the Ubuntu art team.
Tab design on Australis (Thunderbird v15+):
If you don't really like the curved tabs of the Australis design and want to use squared tabs, similar to Thunderbird v14 and prior: Perhaps you might try my small and simple extension Squared Australis Tabs (Tb).
I hope you like it. Have fun! :-)
Please report bugs and feel free to make suggestions to improve this theme.
To contact me just send a mail.