James;
So get a PBX that does VPIM, and dial into it.
Our current solution is very similar to this, and has multiple
problems, the most important being that it is much more complicated
for the end-user than it needs to be.
It needs to be complicated.
The simple and straight forward way to transmit audio over phone network
is to use voice channel.
But, it has nothing to do with IETF nor the Internet.
You think MIME audio attachments work over iMODE but not over WAP.
I don't know what the new Docomo products do; that's why I'm asking.
This problem is not specific to VPIM, or email; the mobile aspects
(e.g., the lack of mobile carriers providing end-to-end Internet)
form a problem bigger than the IETF.
Your problem may be 25 times bigger than IETF.
But, it is your probelm and has nothing to do with IETF.
Masataka Ohta