Imports System.Net
Imports System.Net.Mail
 
' ...
 
Private Sub btnSend_Click(ByVal sender As System.Object, ByVal e As _
  System.EventArgs) Handles btnSend.Click
   Try
     ' Mail "zusammen basteln"
     Dim m As New MailMessage(txtFrom.Text, txtTo.Text, txtSubject.Text, _
      txtMessage.Text)
 
      ' SmtpClient instanzieren mit SMTP-Adresse des Servers
      Dim sc As New SmtpClient("smtp.web.de")
 
      ' Credential erzeugen und initialisieren
      Dim cred As New NetworkCredential("benutzername", "passwort")
 
      ' Credentionals den SmtpClient zuweisen
      sc.Credentials = cred
 
     ' Nachricht senden
      sc.Send(m)
 
      MessageBox.Show("Senden erfolgreich")
   Catch ex As Exception
      MessageBox.Show(ex.Message)
   End Try
End Sub

Ralf