Serving a movie

I have just purchased a X Server 10.4 MAC OS. I am trying to serve a movie (product demo) from the apple server to the internet. I placed the file in Library\Webserver\Documents\Demo_1.mov Inside the network it starts to play right away, but outside the network it downloads the whole movie before it start to play. It is a 18 MB file. Is there a way to speed this up for the internet? My upload speed is 800KB.