MP4'a have to render a frame at a time so you can't use Multi Machine rendering for that kind of task unless you have some very specialized hardware/software combinations. The AE network rendering is limited to a few mezzanine codecs and image sequences.
You can cut the movie up into pieces and send each part to a different machine and then have those parts stitched together when the render is done by using a new product for AE called Render Garden. I'm using it for a most of my renders now. Check out the informational videos at the bottom of the product page and if you decide to try it and it works for you, you can thank my friend Matt Silverman and his friends for their amazing work. I'm cutting most of my render time by about 70%. I am not using it on multiple machines yet, just utilizing all but one of the cores on my main machine. Leaving one core so I can continue to work in AE while things render.