My maytag duet washer releases a rotten egg smell each time if it was not in use for a day or so.Any idea why?

This comes from the residual water that sits in the bottom of the wash tub and drain lines, or you may have something lodged in the rubber bellow (rubber door gasket) or drain pump. The residual water is normal and required to keep sewer gases from seeping into the wash drum through the drain lines. The water acts as a vapor seal. What can cause this water to sour is closing the washer door when not in use. Because of the tight seal on these washer doors, it is highly recommended that you leave the door open to allow the tub to air while not in use. The following link explains some other things you may consider:

http://www.fixya.com/support/r513372-front_loader_mildew_odor

I know this becomes a sore subject with some people, because some of this information was not mentioned by the manufacturer in earlier models of the Whirlpool Duet or Kenmore Elite. Much of this information was learned thorugh trial and error by technicians in the field and customer complaints/concerns. It was later supposed to be added to the documentation in the newer models to ensure the consumers knew the proper care procedures. I personally own one of these washers and have never had a problem with odor or mildew in the 9 years I've had it, following this regiment.

If you suspect you may have to clean out the drain pump, the following link explains how:

http://www.fixya.com/support/r385845-checking_drain_pump_in_whirlpool_duet

Start by checking the rubber bellow around the door, check the drain pump for debris, leave the door open when not in use and run a clean cyle once in a while if you do not routinely use hot water cycles. This kills unwanted bacteria and will keep mold, mildew and odor from forming. If you have any questions, please let me know. I hope you find this information helpful.

NOTE: If the rubber bellow becomes permiated with mold, it often will not come out (even with scrubbing). If this is the case with your washer, you may have to replace the bellow.

They sell this powder cleaning solution that you can use to clean your washer and it does eliminate the odor. I bought mine at Target it's from Tide they sell a small box with about 3 small packages. You can read the instructions on the box it's very easy to use.