Stunnel listen on WAN interface instead of IP

[Blinkiz]

Hi
I have a service running on my LAN computer that listen on HTTP 8080. Installing the package stunnel enables me to connect to that service on HTTPS 8080.

In the stunnel configuration it exist 5 textboxes. One is "listen on IP". This one should be the IP of the WAN.

My request is to be able to choose to "listen on WAN IP" and not entering any IP. This way the IP will be correct even if my WAN IP is changed.

Thank you