Assegnate 4 su 5 stelle

compatible with which version of thundrbird ??? I try 7.01 and 9.01

Compatibility is written in information version. Furthermore, you should have read addon description : Please note also there won't be any version compatible for newer versions of TB above v3.2a1pre. If you intend or are using a higher TB version, please consider using Auto Resize Image which offers more features and will be maintained for future TB releases (Auto Resize JPEG is its prequel).
Regards