23.1403GPPFunctional descriptionMultimedia Messaging Service (MMS)Stage 2TS
The MMS Relay – MMS Relay interface is used to transfer MMs between different MMSEs. Interworking between different MMSEs shall be based on SMTP according to RFC 821  as depicted in figure 5.
Figure 5: Interworking of different MMSEs
All elements of an MM shall be included within a single SMTP message which shall be organised as MIME type application/multipart. All MM elements shall be of standard MIME content types including the MMS header.
This MMS header shall be of registered MIME application class content type. It shall be sent as a distinct part of the SMTP message. In addition to this all header fields but the MMS specific header fields shall be copied into the SMTP message’s header fields.
When conveying an MM the MMS header part shall not be the primary part in the MIME so that non-MMS-aware readers can view this part as merely an attachment. This will minimise problems with presentations of the MM data by these readers.
NOTE: Content type application/mmsheader is subject to registration within IANA. In the mean time content type application/x-mmsheader shall be used to indicate the MMS header.
NOTE: Private agreements may utilise additional connection and security (e.g. IPSec) methods. Such methods are out of the scope of standardisation for R’99.
7 WAP Implementation of MMS
WAP provides significant support for MMS, both in direct service specification and in the underlying technologies. While the WAP MMS service specification work is new and is therefore unavailable for direct reference, its basic approach and limitations are based on WAP documents describing MMS architecture and message encapsulation. This should be done based on the underlying WAP technologies that have been published, and can therefore be referenced.