System.Net.Mail.SmtpException: 'Server does not support secure connections.'

Question

How do i resolve Server does not support secure connections exception? i use this code ,The same code works for my friend ... i try more other port (25 ,465)

                mail.IsBodyHtml = true;
                SmtpClient smtp = new SmtpClient("smtp.gmail.com", 587);
                smtp.Credentials = new System.Net.NetworkCredential("MyEmail", "MyPassword");
                smtp.EnableSsl = true;

                smtp.Send(mail);