I just flew through Schiphol today and was told by the information centre that the info on Jill and James is outdated. However, it is still possible to post a parcel at the airport. You must go downstairs to the Arrivals floor, clear immigrations/customs and then head to Arrivals 3 where you will find "Service Point Schiphol". Make sure you plan your time accordingly if you are transiting because going through customs and back will kill an hour easily.