Found this @
http://forum.xda-developers.com/showthread.php?t=653563 and it actually worked
Go to messages>all messages>menu>settings>options>menu>MMS server>click on SampleMMS>
Server name: T-Mobile MMS
IP: 216.155.165.050
Port:8080
Server Address: 216.155.174.84/servlets/mms or
http://mms.msg.eng.t-mobile.com/mms/wapenc
Connect via: Tmobile MMS
If that still doesn't work then continue to do the following:
Start>Settings>Connections>Connections
1.Click the the Advanced tab
2.Click "select network"
3.On the top drop down click on "T-mobile MMS" and click edit
4.click edit again
5.Click next
6. Change Access point name to: wap.voicestream.com
7. Click next again and then finish.
8.click okay
9.on the top drop down select T-mobile Data then click okay.
You are all done.