Moodle installed on SYNOLOGY NAS : can't access from internet but ok from local network

Hello,

I just installed Moodle 2.3.1.0006 from the packet manager on  my SYNOLOGY DISKSTATION.

The problem is that during the installation, the web adress is greyed out and points to the NAS local IP adress.

When I try to access Moodle from the internet through mydyndns.org/moodle , I have a "sorry message" that redirects to NASLOCALIP/moodle ... (see the screenshot).

Does any one know how to fix this ? I'm stuck.

Moodle is working fine on the LAN though, doing tests with my wife to get use to the platform.

Thanks for your help,

Regards,

Olivier