How? Any more advanced technology must still obey the laws of physics, and if we really are that wrong about the laws of physics, we'd have no way to receive such a message.

Well, there's stuff like wormholes, Alcubierre drives, etc. All problematic given our understanding, but a culture having made breakthroughs towards these might just show up on our doorstep one day.

There are ways to receive messages that don't require the recipient to have the tech. An uncontacted tribe in the Amazon can still be reached by megaphone, or plane.

To be fair, in that situation the tribe can be reached because they DO have the tech: ears, eyes, etc. So we're still contacting them via tech they have.