Bring a large pot of salted water to a rolling boil. Add elbow macaroni and cook for 8–10 minutes until al dente. Drain and rinse under cold water.

In a large mixing bowl, combine mayonnaise and Dijon mustard. Whisk until smooth and season with salt and pepper.

Fold the cooled pasta into the dressing. Add bell peppers, celery, cherry tomatoes, red onion, and sweet pickle relish. Stir until well coated.

Cover and chill the salad in the refrigerator for at least 1 hour before serving.