Xna model parts are overlying others

I am trying to import in XNA an .fbx model exported with blender.

Here is my drawing code

public void Draw(){    Matrix[] modelTransforms = new Matrix[Model.Bones.Count];    Model.CopyAbsoluteBoneTransformsTo(modelTransforms);    foreach (ModelMesh mesh in Model.Meshes)    {        foreach (BasicEffect be in mesh.Effects)        {            be.EnableDefaultLighting();            be.World = modelTransforms[mesh.ParentBone.Index] * GameCamera.World * Translation;            be.View = GameCamera.View;            be.Projection = GameCamera.Projection;        }        mesh.Draw();    }}

The problem is that when I start the game some model parts are overlying others instead of being behind. I've tried to download other models from internet but they have the same problem.