salve
ho questo problema: devo inviare una mail con attachment cricato tramite il controllo FileUpload

if (att.FileName != "")
{
string kk = att.PostedFile.FileName.ToString();
Attachment atch = new Attachment(kk);
msg.Attachments.Add(atch);
}
SmtpClient smtp = new SmtpClient("mail.miodominio.com");
smtp.DeliveryMethod = SmtpDeliveryMethod.Network;
quand carico la pagina, ricevo questo bel messaggio di errore:

Security Exception
Description: The application attempted to perform an operation not allowed by the security policy. To grant this application the required permission please contact your system administrator or change the application's trust level in the configuration file.
cosa vuol dire ???

p.s.:il dominio in questione risiede su aruba.