3proxy Behind NAT: Local Bind Address vs Public Exit IP
Distinguish a proxy host's local bind address from the router's translated public address when configuring 3proxy.
The website sees your router's public IP, but that does not mean the proxy machine can bind a socket to it. Behind NAT, the host often owns only a private address.
3proxy's external address controls the local source used for outgoing connections. If a public address exists only on an upstream router, copying it into a local bind setting can fail before NAT has any opportunity to translate the traffic.
Use an address actually available on the proxy host, or the intended default source-selection behavior. The router can then translate that local connection according to its network policy.
The client-facing listener is separate. It uses an address on which clients reach the host; public inbound access additionally depends on the intended routing or port-forwarding arrangement.
A working local source does not guarantee a particular public identity. Several local addresses can share one NAT exit, and provider policy can change the translated address.
Write down the host address and translated public address as two values. That prevents a website's IP report from being mistaken for an address assigned to the local operating system.