Put the chicken in a large pot with enough water to cover. Bring to a boil; reduce heat to medium. Allow the chicken to simmer until no longer pink at the bone and the juices run clear, about 1 hour. An instant-read thermometer inserted into the thickest part of the thigh, near the bone should read 180 degrees F (82 degrees C). Remove the chicken to a cutting board. Use a pair of forks to remove and shred the meat from the chicken. Discard the remains. Place shredded chicken in a single layer on a plate and allow to cool completely in refrigerator, about 15 minutes.
Stir together the salad dressing and sugar in a large bowl. Stir the chicken and raisins into the salad dressing. Add the mango and gently fold into the mixture. Refrigerate overnight or 8 hours before serving.