No, certified mail and registered mail are two different types of service. Registered mail includes all the same features of certified mail plus a few more. In addition to proof of delivery, you will also receive additional insurance and security with registered mail. Registered mail preserves the chain of custody as the item travels, and it is never left unattended without being locked inside a safe or sealed container. This service is usually reserved for extremely important documents, and it comes with a much higher price tag.