Smelly washing machine!

I always put the detergent drawer in my dishwasher on the top shelf. Gets it nice and clean. I do give it a scrub in the sink first. Also make sure the washing machine filter is clean as a build up can smell. My machine stopped during a cycle and had the emergency light on as it wouldn't drain. Turned out TWO colour catcher sheets had gone through and caused a blockage! I now put them into a zip up washing bag and it's been fine since then. It's a total pain to drain the machine and check the filter because it is only an inch or two from the floor, so hard to get a container under it and it's a nuisance having to remove the plinth below the kitchen units to access it. I always leave the washing machine door wide open overnight after doing a wash load, but not all the time as it would get in the way. All my appliances are integrated.

A washing machine engineer told me to use only powder as the liquid builds up in the machine and causes smells and spotty washing. It is working so far.

I actually switched to laundry liquid instead of powder after my machine started leaking slightly, and the engineer was unsuccessful fixing it. I know about how liquids could build up a coating so I did it deliberately to block the leak and it worked! Been going for several years since then. But a year or so back I decided to use one of those washing machine cleaner packs and the leak started up again, so now I know I can't risk cleaning it any more.

I had this problem, I tried lots of what people have suggested. Started using a biological gel, well known make. Still use softener. No more smell.

I find it solves the problem if you dry the excess water from the rubber seal so no stagnant water to smell.

I changed from liquid detergent to powder just for my whites washes and haven't had a problem since.

In desperation to make the messy, mouldy soap dispenser tray look good again. I pulled it completely out, easy task as there is usually a bit you compress and it comes on out, and put it through a wash cycle of the dishwasher! Problem solved.

Vinegar and water poured in the drawer. And then put on a very hot wash

I had my engineer round to mend my dishwasher and mentioned a smell in my washing machine he suggested two dishwasher tablets at 90 degrees to get rid of smell and mould in machine every few months...works like a dream...

Put the detergent drawer in the dishwasher regularly whilst cleaning where the drawer sits. Wipe the rubber inside the drum after every wash and leave an old flannel in the drum so the door stays ajar. It works for me.

I used to work in the Hotpoint service office and was instructed to tell customers that it is using liquid soap. Apparently liquid soap doesn't kill off the bacteria. Always use soap powder. Fabric conditioner is fine but you must pull out the drawer and clean it now and again. Hope this helps.

The machine has now been cleaned to within an inch of its life with washing soda and 90 degree wash. It's worked! Will now have to rethink my detergent and temperature setting. Thanks for the input everyone.

Are you sure there is a U-bend on your drainage upstand?
I plumbed my washing machine in and didn't think to put in a U-bend under the pipe which sticks up for the drainage pipe to go into. Horrible smell all the time from the drain.
Installed U-bend this weekend - ah, the sweet smell of success!

Laundry Cleanser (Tesco's own) or buy in bulk through Amazon , definitely no fabric softener.
Another tip, if you use 'Colourcatcher' always use a safety pin and attach to one of the garments. This advice was given by a W/MC mechanic after I called him out because the machine wasn't emptying; the colourcatcher was stuck in the filter. Expensive advice but worth knowing.