Place the oxtails in a large bowl. Rub with mustard.
Combine the dry ingredients in a small bowl. Then, rub all over the meat. Cover and refrigerate overnight.
Heat the barbecue to 250Fdegrees. Smoke with apple, cherry and/or hickory chips over indirect heat for 2 hours. Combine the apple juice and vinegar in a spray bottle. Open the smoker and spray the meat.
Continue cooking for 2-3 more hours, until the internal temperature of the meat reaches 180F degrees. Spray liberally with the apple mixture. Remove from the smoker and let rest 15 minutes before serving.