Цитата из инстукции по удалении Mozilla Thunderbird (особенно нравитса Others - это про Linux/Unix:
Uninstalling Thunderbird
To uninstall Thunderbird, follow these instructions:
Windows
From the Start menu, choose Control Panel. When the Control Panel appears, double click Add or Remove Programs. Find "Mozilla Thunderbird (0.6.)" in the list and click Remove to uninstall.
Mac OS X
Drag the Thunderbird application to the Trash.
Others
Remove the thunderbird folder.
