Ok, I have a rack into a colocation. I have seen that there is some cool air from the ground just before the rack. I suppose that I must place the front of m1000e. In this way, the enclosure call pull some fresh air and rejected the hot air. Maybe I'm wrong, I can do the opposite way. If someone can give me some advices?
M1000e is front to back air circulation, so you want to follow best practice of the front facing a "cold aisle" and the rear facing a "hot aisle". And the closer to the bottom of the rack, the better. Colder air, better weight distribution.