11:45AM Pacific — Microsoft confirmed that the digest display problem is the result of a recent update to their systems which introduced a compatibility issue within the component responsible for processing email attachments.  Their engineers have developed a fix and are working on deployment; they could not issue a definitive ETA, but cautioned that the deployment process may take an “extended” period of time.  We have pressed for more definitive information and they have committed to an  informational update by late afternoon Pacific time.  We are also investigating possible changes in the encoding of the digests which could help. In the meantime, Microsoft believes that only a small number of customers are impacted by this, and we can confirm that at least some customers using Office 365 are indeed unaffected.