public static void HandlingMail(List<String> destEmails, String subject, String body)
{
        System.Net.Mail.MailMessage message = new System.Net.Mail.MailMessage();


        foreach (String email in destEmails)
        {
            message.To.Add(email);
        }


        message.From = new System.Net.Mail.MailAddress("unknown@gmail.com");

        message.Subject = subject;


        message.IsBodyHtml = true;
        message.Body = body;


        System.Net.Mail.SmtpClient smtp = new System.Net.Mail.SmtpClient("smtp.gmail.com");
        smtp.EnableSsl = true;
        smtp.Port = 587;
        smtp.Credentials = new System.Net.NetworkCredential("unknown@gmail.com", "password");


        try
        {
            smtp.Send(message);
        }
        catch (Exception ex)
        {
            Console.WriteLine(ex.StackTrace);
            Console.WriteLine(ex.Message);
            Console.WriteLine(ex.InnerException);
        }
        finally
        {
            message.Dispose();

        }
  }


  // Here is the error
  //9/23/2015 8:50:53 PM     at System.Net.Mail.SmtpClient.Send(MailMessage message)
// at Program1.MailHandler.HandlingMail(List`1 destEmails, String subject, String body)
 // 9/23/2015 8:50:53 PM  Failure sending mail.
 // 9/23/2015 8:50:53 PM  System.Net.WebException: Unable to connect to the remote server ---> System.Net.Sockets.SocketException: A socket operation was attempted to an unreachable network [2600:f8m0:4001:d06::9c]:587
  //at System.Net.Sockets.Socket.DoConnect(EndPoint endPointSnapshot, SocketAddress socketAddress)
 //at System.Net.ServicePoint.ConnectSocketInternal(Boolean connectFailure, Socket s4, Socket s6, Socket& socket, IPAddress& address, ConnectSocketState state, IAsyncResult asyncResult, Exception& exception)
// --- End of inner exception stack trace ---
 //at System.Net.ServicePoint.GetConnection(PooledStream PooledStream, Object owner, Boolean async, IPAddress& address, Socket& abortSocket, Socket& abortSocket6)
 //at System.Net.PooledStream.Activate(Object owningObject, Boolean async, GeneralAsyncDelegate asyncCallback)
 //at System.Net.PooledStream.Activate(Object owningObject, GeneralAsyncDelegate asyncCallback)
 //at System.Net.ConnectionPool.GetConnection(Object owningObject, GeneralAsyncDelegate asyncCallback, Int32 creationTimeout)
 //at System.Net.Mail.SmtpConnection.GetConnection(ServicePoint servicePoint)
 //at System.Net.Mail.SmtpTransport.GetConnection(ServicePoint servicePoint)
 //at System.Net.Mail.SmtpClient.GetConnection()
 //at System.Net.Mail.SmtpClient.Send(MailMessage message)