A lock for a door of a motor vehicle is provided having: a closing mechanism designed for coupling with a lock striker for bringing about closing of the door; mechanical opening means for controlling release of the closing mechanism from the lock striker; mechanical means for inhibiting opening which can be selectively activated for rendering the opening means ineffective; and electrical actuator means housed in a fluid-tight way in a single casing having at least one output member which traverses, in a fluid-tight way, a through hole of the casing to interact with the means for inhibiting opening.