click on the link download and install the following application :
it should enable you to open and extract the contents on the winmail.dat files. you may have to drag said file to the application icon when you opened it.
the attatchments are coming from people running bloody exchange servers, who dont adhere to open standards and live in a world they think is only occupied by computers running microsoft based software.
heartfelt props to joshjacobs for writing the software that deals with this issue please go to his site and donate if you find it usefull.