I know when testing (from a desktop computer) the "redirected" link (the one with my domain inserted at the front), it was showing the "insecure" symbol and information when clicked. Today, when testing the same link from a mobile, it is showing as secure.
There is no redirect between http and https. But https works also for your own domains (once you get a "green" checkmark and our servers get some hours to get the SSL-certificate).