Washing comes out smelling horrible! Any ideas?

It is not the washer that is causing the prob, more likely to be coming from waste pipe, and or sink if the pipe is connected to the sink waste pipe.
Check and clean filter in washer if it has one, and remove waste pipe from washer and check outlet is not partially clogged up with sediment and other substances.
If pipe goes into sink waste, then pour a sink pipe cleaning fluid of some description down sink waste.
Also make sure you are not doing too many low temp wshes, as this can cause a prob as well
Do a boil wash at least once a month without clothes in but with powder in.
This is called a maintenance wash, and helps keep the inside of washer clean, and free from smells.
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Thanks.