I wrote support about this (twice now) and got this response:
I spoke w/ one of our senior admin guys and he was under the impression
that it never worked. I apologize for the problems, they’re still looking
into it. We’re not quite sure what the issue is. I apologize for this. If
you need anything else, please let us know.
Argh! I was using the MSN transport faithfully for weeks with no problems.