Getting error while sending a mail using asp.net

msg.From = new MailAddress("test@gmail.com");
       msg.To.Add("test@gmail.com");
       msg.Subject = "test";
       msg.Body = "Test Content";
       //msg.Priority = MailPriority.High;


       using (SmtpClient client = new SmtpClient())
       {
           client.EnableSsl = true;
           client.UseDefaultCredentials = false;
           client.Credentials = new NetworkCredential("test@gmail.com", "test");
           client.Host = "smtp.gmail.com";
           client.Port = 587;
           client.DeliveryMethod = SmtpDeliveryMethod.Network;

           client.Send(msg);
       }

The SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.5.1 Authentication Required.