So here is an interesting issue. Server is 5.0.15 (RHEL 4 32bit). When sending .doc attachments, from the Zimbra webUI, it appears the to somehow corrupt the file. Attached are the error messages from OS X and Windows Vista. The same file sent from Gmail to Gmail works fine. However, Zimbra to Gmail, or Zimbra to Zimbra the file corrupts and yields the attached errors.
The file name has been blured, nothing else.