2005 Mazda 3i heavy white exhaust smoke

My daughter was driving home from work today when she noticed heavy white exhaust smoke. She pulled over,called me. I run over had her start the car and there was heavy white smoke coming from the exhaust pipe. I checked under the hood and saw now problems, fluids good although oil looked like it was over filled. Told her to take home. I followed her and maybe a 1/2 mile down the road the smoking stopped completely. This was highway driving untill we got off at an exit and thats really when I saw the smoke stop. 4 clyinder and approx. 47,000 miles on it