User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130510 Thunderbird/17.0.6
It's great, I missed region based formatter a lot :). One minor thing, I
use UI Theme Feature and dark background, it's seems that formatter keep
colors for text but not for background and preview is not relevant
(white text on white background in my situation).