Colliders Problem

I made a simple model in Blender and imported it into Unity. I told it to generate colliders. And then I gave it a rigidbody in order to fall to the ground. But when I pressed play, it fell through the terrain! Does anyone have a solution? When I made a box collider for it, it fell through that too!

Mesh colliders do not physically collide with other mesh colliders or terrain colliders - this is way too expensive on the physics engine. You need to manually set up a primitive collider on your model, or use an array of child objects with colliders on them. Only primitive shapes will collide with terrain colliders.

I would suggest making your mesh collider convex, but last I heard that feature was being deprecated as of Unity 3, so I wouldn't do that.