A receptacle connector includes an outer housing, an inner housing, and an interface seal. The outer housing defines a cavity configured to receive a plug connector through a mating opening of the outer housing. The inner housing is disposed within the cavity of the outer housing. The inner housing holds a contact subassembly that is connected to a cable. The inner housing includes a sleeve that surrounds a mating section of the contact subassembly. The sleeve is spaced apart from an interior surface of the outer housing by an annular gap. The interface seal is on an outer surface of the sleeve. The interface seal engages an inner surface of a nose of the plug connector within the annular gap to seal an interface between the sleeve of the inner housing and the nose of the plug connector.