Patent ID: 7930541

Claim:
An E-mail communication apparatus which relays an E-mail transmitted from a source to a destination, comprising: a certificate storage unit that stores information indicating a destination and an electronic certificate of the destination in a correspondence; a receiving unit that receives the E-mail in which an address of the source and an address of the destination are specified; an encrypting unit that refers to the certificate storage unit when a transmit command for the E-mail is issued for the E-mail received by the receiving unit, determines whether or not the electronic certificate of the destination of the E-mail is stored and, when the electronic certificate is stored, encrypts the E-mail with the electronic certificate; a request mail generating unit that generates a request mail for requesting the destination to transmit the electronic certificate when the encrypting unit determines that the electronic certificate is not stored; a transmitting unit that transmits the E-mail or the request mail encrypted by the encrypting unit to the destination; a notification unit that transmits a notification mail including information which indicates that the request mail is transmitted to the destination and the electronic certificate is now being requested to the destination to the source of the E-mail when the transmitting unit has transmitted the request mail to the destination; a certificate acquiring unit that determines whether or not an electronic certificate of the source is attached to the E-mail that the receiving unit receives and, when it is determined that the electronic certificate is attached, stores the electronic certificate in the certificate storage unit in a correspondence with the source of the E-mail; and a storage unit that stores an E-mail transmitted from the transmitting unit; wherein the encrypting unit stores the E-mail to the destination in the storage unit as a waiting mail when it is determined that the electronic certificate is not stored, determines whether or not the waiting mail directed to the source is stored in the storage unit when it is determined that the electronic certificate is attached to the E-mail by the certificate acquiring unit and, when the waiting mail is stored, encrypts the waiting mail with the electronic certificate acquired by the certificate acquiring unit and makes the transmitting unit to transmit the encrypted waiting mail.