POP3 and selective download/deletion

[Dino Levy]

Hello!
I'm making a mail program and I have a little problem: I don't know how
to achieve the selective downloads/deletion from POP3 servers. For example,
I want to check whether there is an e-mail with subject:HELLO on my POP3 
server, and all I want for my program to do is to connect to my POP3 server,
check whether that specific mail is on my server, if it is then download
it, and if it isn't then break the connection. Is is possible? With this
kind of information, I could also make my program spam aware ( connect to
POP3, check whether spam mail with known subject or known sender is on
the server, and then delete it ). I really need your help...
Thanks in advance.