Run an empty load with just hot water and bleach. Add 1 cup of bleach to your washing machine and hot water.
Use a clean cloth to wipe off the front loading door after the cycle is complete. Make sure you get the door completely dry.
Use cotton swabs to clean under the rubber seal on the front loading washing machine door. Water gets trapped under this seal and that is where the mold forms.
Clean under the rubber seal with many cotton swabs. Throw them away as you finish.
Dip a cotton swab in vinegar and wipe under the rubber seal with it. You will have to use several more cotton swabs for this process. The vinegar will help kill the bacteria.
Run another empty load but this time use a high efficiency detergent and hot water.