A method of delivering an electronic mail message. A mail server receives and stores a rule from a first user. Thereafter the mail server receives the electronic mail message from a second user comprising a sender. The mail server compares the rule with an email address in a field of the electronic mail message. Responsive to the rule being satisfied the email server takes an action with respect to the email address or the field to form a modified electronic mail message. Thereafter, the email server delivers the modified electronic mail message to a third user comprising a recipient. The first, second, and third users may all be different from each other.