Bring a large pot of salted water to a boil over high heat. Add corn and epazote, and cook (adding more water, if necessary) until corn is tender, about 1 hour. Remove from water and let the corn cool briefly.
Peel back husks and spread 1 tbsp. butter evenly over each ear, then brush with 2 tbsp. mayonnaise and sprinkle with 1⁄3 cup cheese and 1 tsp. chile powder. Serve with lime wedges.