What is a certified letter?
A certified letter is guaranteed by the postal service to be delivered to the recipient. A form is filled out at the post office that contains the name of the sender and the person/place where the letter is sent. The sender receives a receipt and can request they be notified when delivery is made. When delivery is made the a person must sign for accepting the mail. The cost is more than ordinary postage, but it gives the sender proof of having sent the material. Actually the letter is not guaranteed to be delivered to the recipient if it is sent via certfied mail. Anyone who answers the door at the address can sign for the letter if it is not sent via restricted mail, which can only be signed by the recipient or I believe anyone who can produce legal papers of guardianship of said recipient. This method of mailing is also more expensive by several dollars (about 5, I think give or take).