On Tue, Apr 10, 2018 at 7:41 AM, Stefan Eissing
> I advice to debug this step-by-step. First the SSL connection to your Apache. Then the proxy setup. Then any restrictions with "Require...".
+1. It appears curl is using HTTP to talk to your proxy, like a
browser would, but that's not your requirement.Your requirement is to
use HTTPS on that hop (a browser wouldn't).
You could easily verify this with a packet capture and it's no httpd issue.