First, as Richard MacCutchan said you need to learn how to use Google to get basic information.
To get you started here is a nice article on CodeProject about
IMAP and POP3 Clients in C#[
^]
This article on
Simple POP3 Email Class[
^] may also be useful.
After you read some articles on the subject
and write some of your own code if you get stuck feel free to post the code that you are having trouble with and ask a specific question.