The first generation CX-9 had a separate tow package option for FWD models. The AWDs came with it automatically.
The second generation models don't have a tow package option. The owners manual lists the maximum trailer weight as 3500 pounds and the maximum gross combined vehicle/trailer weight as almost 8400 pounds (4400 curb weight + 500 passengers/luggage + 3500 trailer). It also states that the 8400 pound maximum should be reduced by 10% for every 1000 meters of elevation. Using that guidance, above 2500 meters (roughly 8000 feet) the max weight should be less than 6300 pounds. It appears that your trailer is about 2x too heavy to remain within Mazda's recommendations.