An electrical receptacle assembly includes a metallic cage defining a receiving space therein, a receptacle connector unit is received in the receiving space. The receptacle connector unit includes a pair of mating ports. An middle heat transfer unit is located between the two mating ports in a vertical direction. The middle heat transfer unit includes a plastic thermal pad with a pair of heat pipes insert-molded on two sides. The pair of heat pipes extend through a rear wall of the cage and connect to a rear heat sink unit located behind the rear wall of the cage. An electrical plug module assembly equipped with a metallic case composed of the upper part and the lower part each having a heat sink structure unitarily formed on the exterior surfaces.