A method and system are provided for allowing an electronic mail user to block receipt of undesirable electronic mail content. An email user contacts her email service provider via an Internet-based web page. The user may designates certain keywords or text strings and certain email addresses associated with email she considers undesirable. Subsequently, when email messages are sent to the user, those messages are intercepted by the user's email service provider at an email server. A database lookup is performed for the keywords, text strings or email addresses designated as undesirable by the user. The email service provider does not deliver email containing or from the designated undesirable keywords or text strings and certain email addresses. The user may designate a return message to be sent back to the sender of the undesirable email to alert the sender not to send future messages to the user containing the undesirable keywords or text. If desired, in an effort to cause the sender to abandon the user's email address as a target for unsolicited and undesirable email, the email service provider may send a return message to the sender that indicates that the user's email address is not operable and that the email to the user is undeliverable.