invio mail da form usando exchange

[yro]

ciao, utilizzando il seguente form riesco ad inviare mail solo localmente agli utenti interni user@dominio.local.

  Flds("http://schemas.microsoft.com/cdo/configuration/sendusing") = 2
  Flds("http://schemas.microsoft.com/cdo/configuration/smtpserver") = "192.168.0.5"
  Flds("http://schemas.microsoft.com/cdo/configuration/smtpserverport") = 25
  Flds("http://schemas.microsoft.com/cdo/configuration/smtpauthenticate") = 0
  Flds("http://schemas.microsoft.com/cdo/configuration/urlgetlatestversion") = True

ho provato questo metodo per mandarla ad indirizzi email esterni ma va in errore. (su win server 2008 IIS7 non riesco a ricevere il dettaglio dell'errore).

  Flds("http://schemas.microsoft.com/cdo/configuration/sendusing") = 2
  Flds("http://schemas.microsoft.com/cdo/configuration/smtpserver") = "192.168.0.5"
  Flds("http://schemas.microsoft.com/cdo/configuration/smtpserverport") = 25
  Flds("http://schemas.microsoft.com/cdo/configuration/smtpauthenticate") = 0 'cdoBasic
  'Flds("http://schemas.microsoft.com/cdo/configuration/cdoSendUsingMethod") = cdoSendUsingPort
  'Flds("http://schemas.microsoft.com/cdo/configuration/sendusername") = "dominio/utente"
  'Flds("http://schemas.microsoft.com/cdo/configuration/sendpassword") = "password utente"
  Flds("http://schemas.microsoft.com/cdo/configuration/urlgetlatestversion") = True

sbaglio qualcosa nel codice?

Grazie.