Rated 4 out of 5 stars

le ondrej_mocny ar DFómh. 19, 2013 · buan-nasc

I've made a simple app for OSX which displays the Thunderbird icon in the menu bar and the number of unread e-mails next to it. It uses this extension and works quite well. There is also a version with white text for dark menu bars. The only thing is that the extension takes some time (1-2 secs) before it detects the number has changed and writes it into the file.

Check it out here:
http://bitbucket.org/ondrej_mocny/thunderbirdunreadcount