the present invention provides a method and system for warranting electronic mail using a hybrid public key encryption scheme . in one embodiment , the sender contacts an authentication server which first identifies the sender as being allowed to send through the server , and secondly signs his email using a private key in order to send to the recipient . upon receipt , the recipient can then verify that the sender is indeed authenticated by the authentication server by contacting the authentication server , requesting the sender &# 39 ; s public key and using this public key to validate the signature contained in the email . it is possible that the authentication server may itself send the email to the existing mail servers , or it may simply return the signature to the sender for sending to the recipient along with the original email using the sender &# 39 ; s existing outgoing email server .