Thanks a lot for you answer, but unfortunately it didn’t work. When I just import it as a normal static mesh, UE4 uses the smoothing I set in Blender. But whenever I choose “import as skeletal mesh”, it doesn’t. Now I tried to import it with “flat smoothing” and UE4 still shows me the smoothed egdes. It’s really weird…
Edit: Triangulating the faces inside Blender didn’t help either. I also created a new, simplier mesh and tried to export it with both exporter versions (FBX 7.4 binary and FBX 6.1 ASCII). Whatever I do, UE4 smoothes all edges and I always get this “The bone size is too small to create physics asset” warning information.