Mozilla Thunderbird 45.0 ignores glass8 - any ideas?

[Meanjeans]

Hi fellow glass8 fans,

Since the last update to version 45.0 my Mozilla Thunderbird just ignores the glass window frame as well as the button theme. See screenshot.  
With Thunderbird 44.0 and earlier there was no problem. I tried to force a transparent title bar by UserChrome.css (workaround for Firefox to enable glass effect) but it did not work.

Just wondered if anyone knows a workaround or found a solution for this issue?
I guess it has to be fixed within Thunderbird, not within glass8.

I am even willing to switch to another mail program, as long as it can import from tbird and looks good with glass8
(If you have any suggestions?) 

[powerf00l]

You can find a fix for this issue here: https://developer.mozilla.org/en-US/Add-ons/Themes/Common_Firefox_theme_issues_and_solutions