I still have not be able to get drag and drop of Apple Mail to work. I have tried it on a different machine and it is still a no go. In trying to find a workaround I tried dragging a message from Sparrow Mail and it was accepted by TB. Unfortunately the title seems to be the file number not the subject line and opening it in TB is problematical (sometimes yes and sometimes no). Interestingly it is listed as internal in TB.
Brain people please fix the mail problem for us. It mars what is otherwise a great product.