What do you have set for $final_spam_destiny? It should be D_DISCARD if you want amavisd-new to discard the message which has higher score then the kill level.BQ.
*gasp* Oh no! mailgate etc # grep final_spam_destiny amavisd.conf $final_spam_destiny = D_PASS; # (defaults to D_REJECT) mailgate etc # :(Hrm, I shall try that. I'll change it to D_DISCARD and see what happens. Thanks!