試試這個string s_from = TextBox8.Text;
            string s_to = "***@***.com";
            string pwd = "";
            string dominoServerIP = "192.168.*.*";
            int i = s_from.IndexOf("@");
            string username = s_from.Substring(0, i);            MailAddress from = new MailAddress(s_from);
            MailAddress to = new MailAddress(s_to);
            MailMessage mailobj = new MailMessage(from, to);
            mailobj.Subject = "***";
            mailobj.Body = "***";
            mailobj.IsBodyHtml = true;
            mailobj.BodyEncoding = System.Text.Encoding.GetEncoding("GB2312");
            mailobj.Priority = MailPriority.High;            SmtpClient smtp = new SmtpClient(dominoServerIP);            smtp.UseDefaultCredentials = false;
            smtp.Credentials = new NetworkCredential(username, pwd);
            smtp.DeliveryMethod = SmtpDeliveryMethod.Network;