A bit like Gmail/Outlook look&feel, based on chrissi4u's 'CLEAN ADAPTION no1' designed for vertical message view. Note that you will have to adjust the width of the panes for the message list to display correctly. You can also modify the subject column (eg. using the Stylish extension). Not guaranteed to work with every window manager.
A very cleaned-up style for the User Interface only. Inspired by Material design, Outlook and Postbox. Affects the main-interface and the calendar/lightning add-on. Detailed description and comments inside the CSS. Please read the additional information here, or the one inside the code. Updated (1) 15.Dec.2015 - force white titlebar also with cuxtom visual styles.
Dark theme for Thunderbirds main UI. If you have any issues with this style, please open a ticket at https://github.com/NiklasGollenstede/stylish
Thunderbird tabs without curves and gradients
Gets Thunderbird more fit with Windows 8 and Windows 10 looks - sharper tabs, fewer gradients. Customizable.
Some Opera-inspired adjustments of a particular "square tab" theme to fit with Windows 10 better.
A dark Thunderbird theme, fits good with Adapta Gnome3 theme. Based on https://userstyles.org/styles/121860/thunderbird-chris-clean-adaption-no1
A dark view of thnderbird conversation, for use with a dark theme On the screenshot, I also use accountColor
Display calendar a dark way for a use of a dark theme in thunderbird
Thunderbird's (v.2) msg tagging changes the foreground msg color: this style makes a tagged msg stand out by changing its background color. Applies to default and custom tags. Not my own work. Refs: (a) TwisterMc http://www.twistermc.com/blog/2007/04/10/thunderbird-labels http://www.twistermc.com/blog/2007/05/02/custom-thunderbird-labels (b) and The-Daily-Poll (Rassi) http://the-daily-poll.com/wp-content/uploads/2007/05/complete_twistedmc_labels.txt