An electronic file sending method comprising: sending an electronic mail including an encrypted electronic file from a sending apparatus to a first server; encrypting, using a first key, at the sending apparatus a password that is necessary to decrypt the encrypted electronic file and sending the encrypted password to a second server, which is different from the first server, from the sending apparatus; receiving at a receiving apparatus the electronic mail sent from the sending apparatus via the first server; receiving at the second server the encrypted password from the sending apparatus, decrypting the encrypted password, and thus obtaining at the second server the password; storing, in association with each other, at the second server file identifying information identifying the encrypted electronic file and receiver identifying information identifying a correct receiver of the encrypted electronic file; sending, by the second server, a data sequence to the receiver identified by the receiver identifying information; receiving from the receiving apparatus at the second server an encrypted data sequence that is generated by using a second secret key corresponding to a second public key of the receiving apparatus and the second public key of the receiving apparatus; when the data sequence sent to the receiver matches a data sequence that is obtained by decrypting the encrypted data sequence by using the second public key of the receiving apparatus, storing at the second server the second public key of the receiving apparatus in association with the receiver identifying information; and encrypting, at the second server, using the stored second public key of the receiving apparatus, the password and sending the encrypted password from the second server to the receiving apparatus. sending an electronic mail including an encrypted electronic file from a sending apparatus to a first server; encrypting, using a first key, at the sending apparatus a password that is necessary to decrypt the encrypted electronic file and sending the encrypted password to a second server, which is different from the first server, from the sending apparatus; receiving at a receiving apparatus the electronic mail sent from the sending apparatus via the first server; receiving at the second server the encrypted password from the sending apparatus, decrypting the encrypted password, and thus obtaining at the second server the password; storing, in association with each other, at the second server file identifying information identifying the encrypted electronic file and receiver identifying information identifying a correct receiver of the encrypted electronic file; sending, by the second server, a data sequence to the receiver identified by the receiver identifying information; receiving from the receiving apparatus at the second server an encrypted data sequence that is generated by using a second secret key corresponding to a second public key of the receiving apparatus and the second public key of the receiving apparatus; when the data sequence sent to the receiver matches a data sequence that is obtained by decrypting the encrypted data sequence by using the second public key of the receiving apparatus, storing at the second server the second public key of the receiving apparatus in association with the receiver identifying information; and encrypting, at the second server, using the stored second public key of the receiving apparatus, the password and sending the encrypted password from the second server to the receiving apparatus.