System.Net.NetworkCredential.GetCredential C# (CSharp) Метод

        public NetworkCredential GetCredential(Uri uri, String authType) {
            return this;
        }

    public E_mails(string Address, string MesBody, string MesTitle)
    {
        //SmtpClient smtpClient = new SmtpClient("ExchangeServerName", 25);
        SmtpClient  smtpClient = new SmtpClient("PN-MAIL-HTCAS.petroneed.local", 25);
        MailMessage message    = new MailMessage();

        try
        {
            MailAddress fromAddress = new MailAddress("*****@*****.**", "Portal");
            MailAddress toAddress   = new MailAddress(Address, "*****@*****.**");
            message.IsBodyHtml = true;
            message.From       = fromAddress;
            message.To.Add(toAddress);

            //message.Subject = "Notification Message!";
            message.Subject = "Notification Message!  " + MesTitle;
            message.Body    = MesBody;

            smtpClient.UseDefaultCredentials = true;
            System.Net.NetworkCredential nc = CredentialCache.DefaultNetworkCredentials;
            smtpClient.Credentials = (System.Net.ICredentialsByHost)nc.GetCredential("ExchangeServerNameSoll", 25, "Basic");
            smtpClient.Send(message);
            //lblText.Text = "Email sent.";
            //return Toaddress;
        }
        catch (Exception ex)
        {
            //lblText.Text = "Coudn't send the message!\n  " + ex.Message;
        }
    }