US Post Office is located at 10674 W Saint Charles Rd, Sumner, MI. This business specializes in Post Offices. US Post Office is open Mon, 10am-3pm; Tue, 10am-3pm; Wed, 10am-3pm; Thu, 10am-3pm; Fri, 10am-3pm; Sat, 10:05am-11:05am; Sun, Closed and accepts American Express, Discover, Mastercard and Visa.