A method and system for authenticating the sender of a mailpiece is described for identifying certain mailpieces as originating from known trusted senders. In one configuration, biometric information and/or biometric metadata is captured when a user writes on a mailpiece with a digital pen. That data is then compared to reference data in a database. Registrant data is then loaded into storage device on the mailpiece and may be digitally signed and/or encrypted by the trusted third party. In another configuration, a mailpiece includes the signature of a sender and the biometric data includes authentication data obtained from the signature that is compared to the biometric data related to the signature obtained during a sender registration process.