threshold  spam caught  good messages flagged
   0.2       21 / 21          13 / 33
   0.3       21 / 21           5 / 33
   0.4       21 / 21           4 / 33
   0.5       20 / 21           2 / 33
   0.6       13 / 21           1 / 33
   0.7        9 / 21           1 / 33
   0.8        2 / 21           1 / 33
