Why is there an odor in the back of the refrigerator?

The water on the rear wall of the refrigerator compartment is drained into the water collector behind the machine through the through-hole pin (drain hole) in the middle lower part of the rear wall of the refrigerator compartment. The water contains many impurities, which may give off a smell after evaporation. After the power is off, remove the backplate of the press and wipe clean the foreign matter in the bottom water collector.