usually caused by breeding mould/bacteria and lots of low temp wash programmes
a service wash may help may/not do a wash with no clothes in ,wipe around door seal rubber with neat bleach in the cracks then wash at 90 degree selected with washing powder strong bleach and vinegar this will kill the bacteria improve the smell
note
the mould may have ate into the door seal making it look unsightly
wirecutterman, June 2010
