Whirlpool has just announced the release of cleaning tablets designed specifically for cleaning high efficiency (HE) washing machines.  These tablets called Affresh, are designed to remove mold and mildew from inside the washer.  Whirlpool claims that due to the efficient design of HE washers, they are more prone to mold and mildew residue. 

 They also mention that all manufacturers recommend monthly cleanings.  Well, I just checked the manual that came with my Bosch Nexxt washer and it specifically says that the inside should not need cleaning and if for some reason descaling(which is not mold and mildew removal) is needed, proceed with caution and follow the product instructions carefully.

I have noticed that the inside of the washer remains damp after every use and that could develop into a smelly problem, but if I leave the door open for a couple hours and let it air out, everything is fine.  I have had the same machine for almost two years and it smells just fine.

I suppose if the problem exists these tablets might be worth a try, but I would suggest prevention first, and then if necessary, be sure to follow the instructions carefully.