Modular connector assembly

A modular connector assembly comprising:

• a header connector comprising a header housing having a base wall and shroud walls extending from the base wall and defining a cavity, the base wall being configured to be mounted to a header circuit board, the header housing holding a plurality of header signal contacts in the cavity, the header signal contacts being arranged in pairs, the header housing holding a plurality of header ground shields in the cavity, each header ground shield at least partially surrounding a corresponding pair of header signal contacts;
• a receptacle connector received in the cavity and coupled to the header connector, the receptacle connector comprising a receptacle housing having a mating end and a mounting end opposite the mating end, the mating end being configured to be mated with the header connector, the mounting end being configured to be mounted to a receptacle circuit board, the receptacle housing having a plurality of individual chambers separated by chamber walls, the receptacle connector comprising contact assemblies received in corresponding chambers, each contact assembly having a dielectric body holding a differential pair of receptacle signal contacts, the receptacle signal contacts being configured to be terminated to the receptacle circuit board, the receptacle signal contacts being configured to be mated with corresponding header signal contacts of the header connector, each contact assembly having a receptacle ground shield coupled to an exterior of the dielectric body, the receptacle ground shield providing electrical shielding for the differential pair of receptacle signal contacts from other pairs of receptacle signal contacts, each receptacle ground shield being mated with a corresponding header ground shield.