Management of broadcast-distributed data entities

A method, computer program product, and data processing system for reducing the storage needed for broadcast-distributed data entities, such as electronic mail messages from a mailing list, are disclosed. Locally stored data entities that are determined to have corresponding copies elsewhere are replaced with identifying information to allow the corresponding copies to be retrieved. In a preferred embodiment, locally-stored electronic mail messages in an electronic mail server that are determined to come from archived mailing lists are replaced periodically with one or more URLs (Uniform Resource Locator) of archived copies of the message. When a request from a mail client to download the electronic mail message is received, the message is reconstructed from the archived copy and returned to the client, rather than being retrieved from local storage.