As everyone else has said, general rule of thumb is to Google the information they HAVE provided in order to figure their address out.

Only once was I unable to do that, because the buyer put their suburb as Sydney, and their street name was in four different Sydney suburbs, none of which matched the postcode they had provided. In other words, it was a total dog's breakfast, so that person's order wasn't posted until they figured out where they lived and were able to communicate it to me satisfactorily.