How do I get only pop3/smtp packets using winpkfilter?
You will get all packets with WinpkFilter but you can selectively process SMTP/POP3 packets. In order to implement this you have to parse packet headers (Ethernet, IP, TCP) and check source/destination ports for SMTP/POP3 ones (25/110).
How do I decode raw packets to see the content? Where may I find more VB examples of using that?