how to send email on selecting the check box

<asp:checkbox id="checkbox1" runat="server" xmlns:asp="#unknown">
                    AutoPostBack="True" /></asp:checkbox>

if(checkbox1.Checked==true)
{
  //call method for sending mail
}

if( checkbox1.checked==true)
{
try
       {
           MailAddress fromAddress = new MailAddress(txtEmail.Text, txtName.Text);


           smtpClient.Host = "localhost";


           smtpClient.Port = 25;


           message.From = fromAddress; message.To.Add("123@gmail.com");//here you have to pass checkbox text or toaddress
           message.Subject = "Hello";





           message.IsBodyHtml = false;


           message.Body =  pswd;


           smtpClient.Send(message);

           Label1.Text = "Email successfully sent.";
       } 
}

protected void CheckBox1_CheckedChanged(object sender, EventArgs e)
    {
//write mail code here
    }