Hi, when wring the address you should firstly put the receiver's name, the mail box number of your class, and then your college or department name, then the university name(make clear the campus name, since many universities in China have more than one campuses nowadays). And don't forget the postal code. Are you mailing things from your home to the university? Make sure the postal code, the mail box number and the university name including the campus name (if any) has been written correctly. You can ask some of your Chinese friends for help.