First, you should send an email to test your configuration. To send an email, hit Ctrl+N, select the Compose new message icon (the empty sheet of paper) or select the Message->New Message menu item. The Composer window will appear. Fill in the To: field with your email address and type something in the Subject field. Send the mail by selecting Message->Send.
To check your email, select File->Check Mail In the lower right corner of the main window, a progress bar will indicate how much mail is being downloaded. If you receive the message you just sent, then congratulations! If, however, you receive any error messages while testing your setup, make sure that your network connection is working and recheck your settings by selecting Settings->Configuration...