That code won't send. Port 465 (and for Gmail it is 587) are not open connections. They both have security on them. You must authenticate with your Gmail user/password before sending anything.
Serial.println ("connecting");
if (client.connect (server,465)) {
Serial.println ("connected");
client.println ("Hello @gmail.com");
// server replies with "Hello. Start your TLS"
delay (x);
// you don't start your TLS, so the server sends "400 error - If no TLS, then no send"
// you continue to attempt the send anyway, and it keeps replying with 400 errors.