I also got T-Mobile USA to send me three test MMS messages. I only received one out of the three and it was about a day late. On top of that I had them cross-check my settings in fMMS ( access point, MMSC, user name, password, HTTP proxy and port number ) using the Nokia N95 as a reference, ( they don't support the N900 ) and everything checked out OK. That said, when I tried to download the test MMS message that got to me I got the same "Unable to retrieve message" error from fMMS.