The security involved in using a forwarding address is a major consideration in choosing a postal service for sending private communications. Using the USPS or a private mailing company involves different risks and considerations. Stop and consider these risks before taking another step. Consider whether you’ll be forwarding to a new home, or to a mobile target. Does the delivery need to be scheduled for time sensitive material? There’s so many considerations and the one thought that stands above them all is security, especially if privacy for a business organization is involved. Is your address subject to forwarding address search methods? Is it even possible, among this vast system of letters and packages that your alternate address can be searched via a forwarding service?
You want answers to these questions and a private mail company will provide you with these answers, just as the United States Postal Service, or any of the other major mail provider can, though the answer may involve a longer search due to the sheer size of the postal service.