A method for enabling the recipient of electronic mail (e-mail) to authenticate the originator of the e-mail without opening the e-mail, so that e-mail that carries a computer virus which activates upon opening the e-mail may be rejected. The originator and the recipient agree beforehand on a privately held authentication code, which is carried in an open field of the e-mail, i.e., carried in a field that is visible to an agent of the recipient without opening the e-mail.