This is the safest horse fencing there is. I put the electric on 5 inch extenders, top and middle of the fence because I have one who loves to drag down mesh. Unlike the picture, I fasten the mesh to the boards and the posts so she can't just walk up and put one big old foot on it and squish.
Post and rail will get chewed to toothpicks by the beavers, er horses, if it's not electrified.
Most of the post and rail I've seen around here looks like this: