The smell hit me the day I pulled out a load of supposedly clean towels and they came out smelling like a damp basement. I washed them twice more before I realized the problem was not the laundry. It was the machine.

Front loading washers are great until the rubber seal starts holding water, and then they turn into a mold farm.

Where the smell actually lives

Pull back the rubber gasket around the door and look inside the folds. That is where water, lint, and hair collect, and where the musty smell starts. It never dries out on its own.

The clean that works

1. Wipe the inside of the gasket with a cloth dipped in white vinegar.
2. Spray the folds with a mix of one part bleach to ten parts water, or use a vinegar and baking soda paste if you want to skip bleach.
3. Scrub the folds gently, then wipe everything dry.
4. Run an empty hot cycle with two cups of vinegar in the drum.

I do this once a month now and the smell has not come back. The trick is the drying step. A washer that stays sealed shut between loads never gets a chance to air out.

The habit that prevents it

The single best thing I changed was leaving the door open after every load. I also pull the detergent drawer out a couple inches so it can dry. And I stopped leaving wet clothes sitting in the drum for hours.

My first attempt at fixing this was just running a hot cycle with nothing in it. That helped for about a week. The smell came back because I never cleaned the gasket itself. You have to get the crud out of the folds, not just rinse the drum.