In Message Audit Logs you have noticed that the Logical IP value is always the same as the Connection IP (Accepted From) value, even when the connection IP is an Internal Mail Host and the message originated from an external source.
The Messaging Gateway is not installed on the network perimeter and messages are accepted from an Internal Mail Host.
Reputation features have been disabled.
The process that collects the Logical IP for reporting comes from the Reputation features. If all the Good and Bad Senders groups of the Reputation section are disabled, then the Logical IP will not be reported and will list as the Connection IP.
At least one of the Good or Bad Senders groups must be enabled for the Logical IP to be reported. The list for the feature can be empty so that it does not trigger, but it must be enabled: