How to delete unwanted email without downloading it?

[Josef Lowder]

In the ongoing (endless) battle against spam, I am trying to create filters 
to block as much of this garbage as possible, but I can't figure out how to 
get the Kmail "Configure POP filters" to  "Delete mail from server" without 
downloading it from my email service provider to my system. 

What am I doing wrong? 

I choose "Match any of the following" select "Subject" and "contains" and 
enter a word or phrase such as "microcap" or "Small Stocks" and for the 
filter action, I choose "Delete mail from server", then click "Apply" and "OK" 
... but this does not stop the identified subjects from being downloaded to 
my system. 

Why? 

How can I get this to work?