Hi everyone,

I'm using a TP-Link Omada ER7412-M2 router and have successfully set up an L2TP VPN client connection to obtain a static public IPv4 address from my provider.
The VPN works correctly, and my outgoing traffic is routed through the VPN interface, with the static IP visible externally. I've configured Policy Routing accordingly, and it works well.

Now, I want to expose a mail server hosted on an internal Debian server.

To do this, I need to forward ports such as 80, 443, 25, 587, and 993 to the mail server.

In the Port Forwarding settings, I cannot select the VPN interface (L2TP client) as the WAN Interface. The only available option are my main and backup WAN.
As a result, incoming connections to the VPN public IP are either dropped or forwarded to the router itself (I see the router's admin page when accessing my domain from LAN).

My questions:

1. Is it possible to forward incoming connections from the VPN (L2TP client) interface to internal hosts?
2. Is there any workaround or hidden option to make port forwarding work on the VPN interface?

Thanks in advance!

Best regards