Once a month, add a cup of Distilled White Vinegar & 1 Cup of Baking Soda directly into the drum and use HOT water for washing. Then, I add about ½ cup of vinegar into the fabric softener compartment and ½ cup of baking soda into the detergent compartment. Set the wash on “Quick Wash” with HOT water and High Spin Cycle. If the mold situation is really bad,use bleach instead of vinegar and baking soda. But make sure you run a few empty cycles just with hot water before doing a load of wash.
A lady at the post office taught me this trick and I have realized very few people know about it! You can turn a flat rate envelope into a pouch to increase the capacity. It holds more than a small flat rate box ($5.80) and about as much as a medium ($12.35) for only $5.60. So worth it! I do this all the time! Just fold the bottom both ways, and flatten it out from the inside, folding the corners and taping them up into a rectangular bottom. Secure with lots of tape. Happy shipping!