A server transmits a message and attachments from a sender to a recipient. A hash is provided of (a) the message, (b) an identification of the sender and (c) a hash of the attachments to form a data string. Instructions may be included for the recipient to send a hashed encryption of the string to a website at the server by registered electronic mail which provides options to obtain other electronic advantages. To authenticate the message, the recipient transmits the message, the attachments and the hashed encryption of the string to the server website. The server decrypts and detaches the hashed encryption of the string to provide a first string and hashes the message, the sender identification and the hashed attachments in the first string to form a second string. The server also detaches and hashes the attachments from the message received at the server website to form first hashed attachments and detaches the hashed attachments from the string to form second hashed attachments. When the first and second hashed attachments match and the first and second strings match, the server authenticates the message to the recipient.