Code

SmtpClient Smtp = new SmtpClient("smpt.yandex.ru", 25);
Smtp.Credentials = new NetworkCredential("Ангелина Глебова", "17011948.Glebova");
Smtp.EnableSsl = false;
//Формирование письма
MailMessage message = new MailMessage();
message.From = new MailAddress("Angelina.G17@yandex.ru");
message.To.Add(new MailAddress("stark2015.dm@list.ru"));
message.Subject = "title";
message.Body = "body";
Smtp.Send(message); //отправка