SmtpClient smtpCli = new SmtpClient();
            smtpCli.UseDefaultCredentials = false;
            smtpCli.Credentials = new NetworkCredential("newsletter@abcdef.com.tr", "********", "abcdef.com.tr");
            smtpCli.Host = "111.111.111.111";  //Sunucu ve gönderim hesabının bilgileri burada giriliyor.
            smtpCli.Port = 25;
            smtpCli.EnableSsl = true;
            smtpCli.DeliveryMethod = SmtpDeliveryMethod.Network;

            MailAddress senderMA;
            MailAddress rcpMA;
            MailMessage mail;

            senderMA = new MailAddress(sender, senderDisp);
            rcpMA = new MailAddress(rcp, reciepentDisp);
            mail = new MailMessage(senderMA, rcpMA);
            mail.BodyEncoding = Encoding.UTF8;
            mail.IsBodyHtml = true;
            mail.Body = data;
            //mail.SubjectEncoding = Encoding.UTF8;
            mail.Subject = subject;
            mail.ReplyTo = senderMA;
            mail.Priority = MailPriority.Normal;

            smtpCli.Send(mail);