F{LocalIP} /etc/LocalIP
The /etc/LocalIP file holds a list of network IP addresses that are considered "local", so that email from any of these networks will always be relayed. An example would be:
205.157.137 209.49.153 209.49.154 127.0.0.1
IP addresses may be listed in one to four parts to indicate a class A, B, or C network or a specific machine.