// Generate test Mail:
 public static Mail randomMail() {
   Mail m = new Mail();
   m.generalDelivery = Enums.random(GeneralDelivery.class);
   m.scannability = Enums.random(Scannability.class);
   m.readability = Enums.random(Readability.class);
   m.address = Enums.random(Address.class);
   m.returnAddress = Enums.random(ReturnAddress.class);
   return m;
 }