This is caused by using too much soap, the wrong soap, or both. Most washing machine manufacturers state that, depending on the water hardness, you should use approx. 1 tablespoon of regular strength soap, 1/2 of that if 2x concentrated, this of course is dependent upon how dirty/greasy your clothes are, but this is a guideline as a starting point.
Also, it is recommended to keep the door open when not in use, though it doesn’t have to be wide open, 4-6″ would be sufficient unless it is more convenient to keep it fully opened. Prevention is always the best medicine, but if the problem has already started, there are some commercial products that you can use to get the smell out. We sell Washing Machine Magic and Affresh. Depending on how strong the odor is, it may take more than one treatment to completely remove the smell.
The discoloration on the boot seal caused by the mold is usually permanent, though it will fade somewhat with the passage of time. Usually, the only way to remove it completely is to replace the boot, though this would be done for cosmetic reasons, as it rarely effects the performance of the part. They also suggest wiping the boot area dry when you have finished washing for the day, being sure to wipe off the glass, especially in the seal area, and inside the boot by carefully pulling it back while wiping it dry. Doing these things, along with using the Extra Rinse option each load, will go a long way in preventing Stinky Washer Syndrome.