Panther’s copy of Mail has a bug where junk email is recognised but not moved to the Junk folder, even when automatic mode is selected, if no other rules are present (i.e. non-junk rules). A workaround is to create a dummy rule. Mine says something like:

if from is equal to “vdssb 1 3208222vb3vb33097”
and from does not equal “vdssb 1 3208222vb3vb33097”
set the text colour to red

Silly, but effective.

Thanks to “Jon” who posted this workaround on Jim Bassett’s weblog.