Canada Post as no jurisdiction unless it's an explosive or a flammable.
As the others said, just wrap it correctly so that it doesn't burst open while being handled like any other item and everything will be fine.
Funny story (maybe not so funny), I know someone who ordered two semi auto assault rifles from a retailer. They were shipped in unlocked gunbags and arrived safely to his post office without any problems or questions. These are real firearms ready for use, just no ammo. So dont worry to much about your Airsoft, everything should be fine