Abstract: A method for tracing an electronic mail message to determine when the recipient has opened the message is disclosed. A server is provided which intercepts e-mail messages intended for the recipient. The server modifies the e-mail to add HTML code to the message and forwards the message to the recipient. The HTML code causes the recipient's mail client program to request a file from the server. When the server detects the request, it knows that the mail message has been opened and thereafter informs the sender. Several other embodiments are also disclosed.