How to send SMTP email at c++ CLR

//Source.cpp
#include "stdafx.h"
#include "Gmail.h"

using namespace My19112014;

[STAThreadAttribute]
int main(array<system::string ^=""> ^args)
{
// Enabling Windows XP visual effects before any controls are created
Application::EnableVisualStyles();
Application::SetCompatibleTextRenderingDefault(false);

// Create the main window and run it
Application::Run(gcnew Gmail());
return 0;
}

//Gmail.h
#pragma once

namespace My19112014 {

using namespace System;
using namespace System::ComponentModel;
using namespace System::Collections;
using namespace System::Windows::Forms;
using namespace System::Data;
using namespace System::Drawing;
using namespace System::Net::Mail;

///

/// Summary for Gmail
///

public ref class Gmail : public System::Windows::Forms::Form
{
public:
Gmail(void)
{
InitializeComponent();
//
//TODO: Add the constructor code here
//
}

protected:
///

/// Clean up any resources being used.
///

~Gmail()
{
if (components)
{
delete components;
}
}
private: System::Windows::Forms::GroupBox^ groupBox1;
protected:
private: System::Windows::Forms::Label^ label2;
private: System::Windows::Forms::Label^ label1;
private: System::Windows::Forms::TextBox^ passwordBox;

private: System::Windows::Forms::TextBox^ emailBox;

private: System::Windows::Forms::GroupBox^ groupBox2;
private: System::Windows::Forms::TextBox^ portBox;

private: System::Windows::Forms::Label^ label4;
private: System::Windows::Forms::Label^ label3;
private: System::Windows::Forms::TextBox^ smtpBox;

private: System::Windows::Forms::GroupBox^ groupBox3;
private: System::Windows::Forms::Label^ label6;
private: System::Windows::Forms::Label^ label5;
private: System::Windows::Forms::TextBox^ subjectBox;

private: System::Windows::Forms::TextBox^ toBox;

private: System::Windows::Forms::ProgressBar^ progressBar1;
private: System::Windows::Forms::TextBox^ attachBox;

private: System::Windows::Forms::Label^ label7;
private: System::Windows::Forms::TextBox^ isiBox;

private: System::Windows::Forms::Button^ button2;
private: System::Windows::Forms::Button^ button1;
private: System::Windows::Forms::OpenFileDialog^ openFileDialog1;

private:
///

/// Required designer variable.
///

System::ComponentModel::Container ^components;

#pragma region Windows Form Designer generated code
///

/// Required method for Designer support - do not modify
/// the contents of this method with the code editor.
///

void InitializeComponent(void)
{
this->groupBox1 = (gcnew System::Windows::Forms::GroupBox());
this->label2 = (gcnew System::Windows::Forms::Label());
this->label1 = (gcnew System::Windows::Forms::Label());
this->passwordBox = (gcnew System::Windows::Forms::TextBox());
this->emailBox = (gcnew System::Windows::Forms::TextBox());
this->groupBox2 = (gcnew System::Windows::Forms::GroupBox());
this->portBox = (gcnew System::Windows::Forms::TextBox());
this->label4 = (gcnew System::Windows::Forms::Label());
this->label3 = (gcnew System::Windows::Forms::Label());
this->smtpBox = (gcnew System::Windows::Forms::TextBox());
this->groupBox3 = (gcnew System::Windows::Forms::GroupBox());
this->button2 = (gcnew System::Windows::Forms::Button());
this->button1 = (gcnew System::Windows::Forms::Button());
this->progressBar1 = (gcnew System::Windows::Forms::ProgressBar());
this->attachBox = (gcnew System::Windows::Forms::TextBox());
this->label7 = (gcnew System::Windows::Forms::Label());
this->isiBox = (gcnew System::Windows::Forms::TextBox());
this->label6 = (gcnew System::Windows::Forms::Label());
this->label5 = (gcnew System::Windows::Forms::Label());
this->subjectBox = (gcnew System::Windows::Forms::TextBox());
this->toBox = (gcnew System::Windows::Forms::TextBox());
this->openFileDialog1 = (gcnew System::Windows

cont--

private: System::Void button1_Click(System::Object^ sender, System::EventArgs^ e)

{

openFileDialog1->ShowDialog();
openFileDialog1->Title = "Choose A File To Attach";
attachBox->Text = openFileDialog1->FileName;
}

private: System::Void button2_Click(System::Object^ sender, System::EventArgs^ e)

{


String ^ username;
username = emailBox->Text;
String ^ password;
password = passwordBox->Text;
String ^ server;
server = smtpBox->Text;
String ^ to;
to = toBox->Text;
String ^ subject;
subject = subjectBox->Text;
String ^ body;
body = isiBox->Text;
String ^ attachment;
attachment = attachBox->Text;
progressBar1->Value = 1;
SmtpClient^ smtpserver = gcnew SmtpClient();
progressBar1->Value = 10;
MailMessage^ mail = gcnew MailMessage();
progressBar1->Value = 20;
Attachment^ at = gcnew Attachment(attachment);
progressBar1->Value = 30;
smtpserver->Credentials = gcnew Net::NetworkCredential(username, password);
progressBar1->Value = 40;
smtpserver->Port = 587;
progressBar1->Value = 45;
smtpserver->Host = server;
progressBar1->Value = 50;
smtpserver->EnableSsl = true;
progressBar1->Value = 55;
mail->From = gcnew MailAddress(username);
progressBar1->Value = 60;
mail->Attachments->Add(at);
progressBar1->Value = 66;
mail->To->Add(to);
progressBar1->Value = 70;
mail->Subject = subject;
progressBar1->Value = 80;
mail->Body = body;
progressBar1->Value = 90;
smtpserver->Send(mail);
progressBar1->Value = 100;
MessageBox::Show("Pesan telah dikirimkan","Terkirim");

}
};
}

nope, it's valid username and id