1. A system for processing message threads, comprising: a thread module to group a plurality of messages, each comprising a message body, by conversation thread; a comparer module to compare the message bodies of the messages; a near duplicate module to identify each message recursively contained in at least one other message as a near duplicate message; an attachment module to generate an attachment sequence for at least part of each attachment associated with one or more of the messages; an attachment comparer module to compare the attachment sequences associated with the near duplicate messages; and a unique attachment module identifying each near duplicate message having an attachment sequence not matching the attachment sequence of any other near duplicate message as a unique message.