A hash module of a mail sender creates a hash data context structure. The hash module processes the headers and the body of an e-mail message in the order required, for example by the DKIM specification, until the data to be hashed has been input. The hash module converts the context structure into printable characters and the encoded structure is transmitted over the Internet or other network to the next participating system. The token authority's hash module decodes the context back into binary form. After ensuring business logic is satisfied, it generates additional headers required for signature, which are then added to the developing hash. The hash module finalizes the hash function and creates the hash value. The authorization module creates the signature and returns it to the e-mail module, which attaches the signature to the message and transmits it to the destination mailbox provider, which verifies the token.