United States Post Office 28081 Marguerite Pkwy, Mission Viejo, CA92690 The United States Post Office is located on Marguerite Parkway, just behind the Shops at Mission Viejo. This branch…More has a variety of services including online P.O. boxes, express delivery and shipping. This is also a passport application center and has automated shipping kiosks. Outside, there are 4 drive-thru mail boxes for standard letters and oversized packages, so customers do not even have to get out of their cars. The service here is both efficient and friendly and the line usually takes no more than ten minutes. The last daily collection is 5pm.