De-duplicating attachments on message delivery and automated repair of attachments

Systems and techniques of de-duplicating file and/or blobs within a file system are presented. In one embodiment, an email system is disclosed wherein the email system receives email messages comprising a set of associated attachments. The system determines whether the associated attachments have been previously stored in the email system, the state of the stored attachment, and if the state of the attachment is appropriate for sharing copies of the attachment, then providing a reference to the attachment upon a request to share the attachment. In another embodiment, the system may detect whether stored attachments are corrupted and, if so, attempt to repair the attachment, and possibly, prior to sharing references to the attachment.