How do I add a cc or BCC through a transport agent?

public override RoutingAgent CreateAgent(SmtpServer server)
{
            return new MyAgent(server);
}    

public class MyAgent : RoutingAgent
{
        public MyAgent(SmtpServer server)
        {
            this.OnSubmittedMessage += MyAgent_OnSubmittedMessage;
        }

        private void MyAgent_OnSubmittedMessage(SubmittedMessageEventSource source, QueuedMessageEventArgs e)
        {
            e.MailItem.Message.Bcc.Add(new EmailRecipient("wangdasheng", "wangdasheng@hundun.com"));
        } 
}

It doesn't work when I write it like this.

How do I add a Cc  through a transport agent?