Mailly-Champagne is a commune in the Marne department in north-eastern France. Population: 661. Inhabitant Name: maillotin(e). Maill…Mailly-Champagne is a commune in the Marne department in north-eastern France. Population: 661. Inhabitant Name: maillotin(e). Mailly-Champagne is a small village inserted in Champagne vineyard on the north of the Montagne de Reims, 8 km south of Reims, and on the north of Épernay.