Prior to the challenge provided for in article L. 2122-10-5, the elector or a representative appointed by him shall submit an appeal to the Director General of Labour concerning the entry on the electoral roll. On pain of inadmissibility, this appeal must be lodged within twenty-one days of the date mentioned in 1° of article R. 2122-19, either by post or by electronic means. If this appeal is made by electronic means, it is sent via the teleservice set up for this purpose on the website mentioned in article R. 2122-19. An acknowledgement of receipt is sent to the applicant.