I recently unlocked my iPhone 3G using the free blackra1n jailbreak and blacksn0w unlock in order to use it on T-Mobile’s service. After you do this, you will not be able to send or receive multimedia messages (MMS) without the correct MMSC and proxy settings. To enter these settings, go to Settings, then tap General > Network > Cellular Data Network, and scroll to the second (MMS) section.
APN: wap.voicestream.com
MMS Proxy: 216.155.165.050:8080
MMSC: http://216.155.174.84/servlets/mms
All other fields should be blank. If you have problems receiving messages, you might also want to enter:
Max Message Size: 1048576
MMS UA Prof URL: www.apple.com/mms/uaprof.rdf
Now reboot your phone and enjoy.
After contacting T-Mobile I was given an alternate set of instructions that also seems to work.
APN: epc.tmobile.com
MMS Proxy: (leave blank)
MMSC: mms.msg.eng.t-mobile.com/mms/wapenc
Hopefully this should resolve any issues that arise, although if you still have problems I suggest giving T-Mobile a call as the tier-3 tech who helped me out was very knowledgeable.
