Léss has it right... the hotter the water in the wash, the better to clean out the inside of the drum/tub and cleanse it of the FOOD that mold eats and flourishes upon.
I have found that STPP also helps to clean out all the residue and limit mold growth/odors in my Neptune front loader. On my Miele front loader, I mostly run 160F or higher wash temps, and haven't had a mold issue. I also leave the door open on the Miele, as well as the detergent dispenser drawer. The Miele only gets cold tap water, the internal heater boosts it to 160+F. When I used fabric softener in it, mold did tend to grow in that compartment, but once I stopped using FS the mold stopped. The Miele rinses so well that the fabrics emerge soft anyway.
The Neptune has a hidden vent in the door as well as in the detergent compartment lid. I have taken to leaving that lid open all the time to encourage air circulation. I don't use FS in the Neptune any more, just distilled vinegar. Seems to work just fine.