Accuracy: why a spam filter that is 99% right can still catch nothing

really spamreally good mailflagged by filter

Flag when score is at least: 50

caught spam (TP)0

spam missed (FN)0

good mail flagged (FP)0

good mail passed (TN)0

accuracy-

precision-

recall-

Drag the slider all the way right: nothing is flagged and accuracy is 95%. Drag it all the way left: everything is flagged and recall is 100%.