An opt-in email system in which a recipient that has opted in to an email list can recognize and trust that an email has actually come from a desired sender. When a recipient desires to opt-in to an e-mail list, the recipient is sent to a trusted third party certification service that generates a certificate associated with a key pair. A key is maintained at the sender's location by a secure cryptographic device that can verify the certificate and create a signature, using a key of the key pair, for messages intended for the recipient. When a message intended for the recipient is received from the sender, the signature will be verified based on the status of the certificate and the corresponding key of the key pair. If the signature does not verify, it indicates that the recipient has not opted-in to receive emails from this sender.