The MMS content is hosted on a public HTTP server which the ISP themselves host (I'm not entirely sure anymore how the synchronization works). Yes, you may call

The MMS content is hosted on a public HTTP server which the ISP themselves host (I'm not entirely sure anymore how the synchronization works). Yes, you may call it a proxy server, but since the data is temporarily cached I call it a proxy server, also the APN settings call it MMS proxy. The definition is pedantic.