Frontend transport on different IP, on-prem, refused connection

Hi there,

We have a need to have our on-prem Exchange accept SMTP from an application. in order to avoid connctor confusion, we figured we could add a new IP to the server, and create a new transport connector on that new IP. When I test on this IP, I receive "No connection could be made because the target machine actively refused it".

New IP has been added to the existing NIC.

I can ping, RDP, etc to that server via the new IP.

Windows firewall is down.

That new front-end connector is the only connector scoped to that new IP address, assigned on port 25.

Exchange 15.2 on-prem.

Any thoughts oh masters of Exchange?