错误：服务器未接受用户凭据

Question

 Pop3Client pop3Client;
 if (Session["Pop3Client"] == null)
 {
     pop3Client = new Pop3Client();

     pop3Client.Connect("pop.gmail.com", 995, true);
            pop3Client.Authenticate("myusername","mypwd",AuthenticationMethod.UsernameAndPassword);
            Session["Pop3Client"] = pop3Client;
 }

  

错误：服务器未接受用户凭据