http://www.rfc-editor.org/rfc/rfc2423.txt
RFC 2423: VPIM Voice Message MIME Sub-type Registration, G. Vaudreuil, G. Parsons1998-09-01T23:00:00-00:00This document describes the registration of the MIME sub-type multipart/voice-message for use with the Voice Profile for Internet Mail (VPIM). [STANDARDS-TRACK]