It was recently clogged for a long time. Then the plumber came and unblocked it and it was fine. It has been draining just fine, with no stench for the past month or so, but now suddenly we get a waft of what smells like raw sewage everytime we run water in the sink. I can’t imagine what is causing it. It’s not clogged. We pour bleach down the overflow hole and in the drain itself. Nothing will get rid of it. It’s gross. I would appreciate any helpful tips! Thanks!