Abstract: The invention relates to a method for creating, and guaranteeing the integrity of electronic messages, within a server providing Internet service. The integrity of the electronic messages are guaranteed and verifiable according to the MIME standard having a header with data regarding routing and regarding content type, an address of the sender and at least one recipient address, and a body comprising a message content. The MIME standard allows the insertion, into the header, of one or more extension fields. These fields comprise a pair formed of one tag allowing the field to be identified and of a value.