Asp.net 2.0 Object reference not set to an instance of an object

Hi when i run my method to send an email out to the user, it throws an error which is "Object reference not set to an instance of an object". I am currently running this on my loachost. Not really sure why is this happening.

I do not have the smtp mail server address and passwords yet, is there a way to run them locally to test if it works without having to key in the actual mail account information?

The Code is:

private void SendPassToUser(string username, string newPassword)
    {
        SmtpClient smtpClient = new SmtpClient();
        MailMessage message = new MailMessage();

        try
        {
            MailAddress fromAddress = new MailAddress("customer@E-COM.com", "E-COM.COM - STORE");
            message.From = fromAddress;
            message.To.Add(username);
            message.Subject = "Resert Password";
            message.Priority = MailPriority.High;
            message.IsBodyHtml = false;
            message.Body = "Your password new password is : " + newPassword;
            smtpClient.Send(message);
        }
        catch (Exception ex)
        {
            Response.Write("Send Email Failed." + ex.Message);
        }
    }

<system.net>
    <mailSettings>
      <smtp>
        <network host="..." port=".." userName=".." password=".." defaultCredentials="true" />
      </smtp>
    </mailSettings>
  </system.net>