Puntuado con 3 de 5 estrellas

ok, nice and interesting idea but what about cache? where extension stores downloaded data, how i can clear it?

Esta valoración es de una versión anterior del complemento (3.2.6.8). 

ThunderBrowse uses the same cache as Thunderbird does. You can clear it via Options < Advanced < Network & Disk Space and click the Clear now button.