How to enable port fowarding on LOCAL network

[packets]

I've pfsense with port forwarding running fine if rules is WAN to LAN but if the rules is LAN to LAN. It doesn't work. I'm using DSL and if WAN is down, local users cannot access the server because the ip on WAN is not available. To resolve this issue, I use dynamic forwarder and point the domain to the LAN Interface of pfsense and create a NAT rule from the LAN interface redirecting port 587 to Server A port 587. Server A has the same subnet of LAN Interface.

Can anyone advise how to implement this? Below is my NAT Rules

[cmb]

You're probably missing source NAT in that case, need manual outbound NAT to translate the source IP so the responses correctly go back to the firewall to be translated back the way the client expects, otherwise you break the TCP session.

[packets]

I'm not familiar with that source NAT. Where I could find it? Is that on the Port Fordward Section?

[cmb]

manual outbound NAT