Encrypted email message structures can contain recipient information that can reveal, to any recipient, all of the other recipients of an email message. Because some recipients, such as recipients to whom the message was “blind carbon-copied”, should remain hidden from the other recipients, individual...http://www.google.fr/patents/US7293171?utm_source=gb-gplus-shareBrevet US7293171 - Encryption to BCC recipients with S/MIME
