Bring a large pot of salted water to a boil and cook the macaroni until tender; drain and rinse with cold water, then shake off excess and set aside to cool.
Chop the hard-boiled eggs, dice the celery, red bell pepper, and white onion.
In a large mixing bowl, combine the chopped eggs, diced celery, red bell pepper, white onion, and sweet relish.
Measure and add the mustard, mayonnaise, sugar, salt, and coriander to the bowl and stir until the dressing is fully combined.
Add the cooled macaroni to the bowl and toss gently but thoroughly so all pasta is coated with the dressing.
Cover and refrigerate for several hours or overnight to let the flavors meld; if chilled, stir again before serving to redistribute the dressing.