When using the special classes of mail always consider that they will probably be slowed down as they logged in at each U.S. Post Office and kept track of by hand. They also require someone to be there to accept the mail piece for delivery confirmation. Additional charges apply for these services.
Registered mail is the most secure mail the postal service offers.
It incorporates a system of receipts to monitor registered articles from the point of delivery to acceptance. This service is not available through the Mail Center. A return receipt provides the sender a proof of delivery, which can be obtained for an additional fee. Certified mail service is available only for first class mail. No insurance coverage is provided.