Combine mayonnaise, relish and mustard in a small bowl.
Sprinkle fish with salt. Place flour in a shallow bowl. Place eggs in another bowl. Combine cornmeal and paprika in a third bowl. Dip fillets in flour, then egg, then cornmeal, shaking off excess.
Warm half of oil in a large nonstick skillet over medium-high heat. Cook fish, working in batches and adding more oil if necessary, turning once, until golden and firm, 2 to 3 minutes per side, depending on thickness. (Wipe out skillet between batches.) Serve with sauce.