Kmail Pop3 filter not deleting from server

[jcwebpost]

I have Kmail 1.6 configured with a pop filter to delete mail from the server 
whenever email contains a X-Spam-Flag that equals YES. Yet, the mail is 
downloaded from the server to my computer anyway. Am I understanding the 
feature wrong? Shouldn't it be deleting the mail on the server instead of 
downloading it?
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