It is a theme for Mozilla Thunderbird, created by me to make Thunderbird "friendler". This is a quite dark theme, based on grey colors with some elements in other colors.
The theme is completly free for personal and commercial use, released under Creative Commons Attribution 3.0.
More smooth and consistent appearance, compatibility with the latest updates of Thunderbird.
It is recommended to install themes directly from Thunderbird (Menu > Add-ons and Themes > Find more add-ons). But sometimes it takes a long time before the new version of the extension is available on the official Mozilla's Add-on website, because every new version has to be approved first.
So, you can download now the newest version of Dark Shadows XT from there, before it becomes available in the official Mozilla Add-ons collection.
To use the theme, first download it and save on disk, and then in Thunderbird go to Menu > Add-ons and Themes > Install Add-on From File, to apply it. Enyoy!
Visit also Dark Shadows XT on official Mozilla's Add-on website
If you are using Dark Night Arcturus X or another theme that defines custom colors for icons of folders, a bug in Thunderbird causes the folder icon to turn black after using the "Repair Folder" option. In such a situation, to restore the correct color of the folder, first disable the theme, then click "Restore default color" in the folder options, and then re-enable the Dark Night Arcturus X theme. The bug has been reported in Bugzilla.