Configuring Mozilla and Thunderbird Junk Mail Settings
After installing the latest Thunderbird software from http://www.uni.edu/its/us/software 
Launch the c:\Program Files\Thunderbird.exe program and configure Thunderbird Settings
For the first few days of operation you must “train” the junk mail filtering by marking and/or unmarking items as being junk so the system “learns” from YOUR preferences.
See Junk Mail Operations documentation.