smtp problem

Hi everybody this is my web.config
for email configuration:
<system.net>
    <mailSettings>
      <smtp>
        <network host="127.0.0.1"/>
      </smtp>
    </mailSettings>
  </system.net>
And this is the code after the buton Send form the email send:
Protected Sub btnSubmit_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnSubmit.Click

        Dim mailMessage As System.Net.Mail.MailMessage = New System.Net.Mail.MailMessage()

        mailMessage.From = New System.Net.Mail.MailAddress(txtFromAddress.Text.Trim())
        mailMessage.To.Add(New System.Net.Mail.MailAddress(txtToAddress.Text.Trim()))
 &nb ...