//*********************************
MailMessage msg = new MailMessage();
msg.To.Add("to@rambler.ru");
msg.From = new MailAddress("from@rambler.ru", "Я", System.Text.Encoding.UTF8);
msg.Subject = "PreveD";
msg.Body = ":)...............messages...............
";SmtpClient smtp = new SmtpClient();
smtp.Credentials = new System.Net.NetworkCredential("from", "pass");
smtp.Port = 25;
smtp.Host = "smtp.rambler.ru";
smtp.Send(msg);
//***************************************************
The SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.7.1 Authentication required
