It quite simple. The message get send to a Hyperspace Buyo or communiation satalite, usally placed on some arms (deltas) of the Hyperspace route and get shot into hyperspace, and if neccessary , from buyo to buyo. See the Problem is not the System to System Communication, but the distance from sender to buyo/ buyo to reciever (which needs a adress). Fringe World, with a not so tight satalite net, can be in communication shadow for some time.
You can intercept message in Hyperspace, but due the massive amount of data, you would need alot of computer power, to discern the different signals, that is the reason, why communication is intercepted in real space, less data, because only specific messages leave the route.
So in Hyperspace communication is possible but troublesome if not specific set up, realtime is possible too, but not always, depends on the distance and specialised equiptment.
So Problem Solved.