You should be more specific. I'm gonna assume you're jailbroken and unlocked already. Now go to the search bar and type "MMS settings T-Mobile"...
You should search before posting there are lots of threads like this. But I'm gonna keep it simple. Nexttime just do some searching first.
Go to Cydia>manage>sources>edit>add>sinfuliphonerepo.com
find MMS and Tethering (T-Mobile) and install it.
Go to settings, general>network>cellular data>reset networks
APN: internet2.voicestream.com or epc.tmobile.com
MMS APN: wap.voicestream.com or epc.tmobile.com
those are the APN's that should show up when done correctly. Reboot your phone. Now you have MMS, you know you did it right when opening Messages you'll see the camera icon by your text box.
P.S. I did give you the more complicated method instead of simply entering the apn manually but that's because what I just gave is also including the fix for blurry MMS on tmo. This method will give you MMS and fix the blurry resolution issue.
Last edited by i.Annie; 11-05-2009 at 11:00 PM.
Reason: Automerged Doublepost
I've never bee able to get my MMS APN to stick. I'll enter it, go back to the network screen then back into the cellular data and it won't be there. Any tips?
I used that same method on my 2g 3.1.2 phone and it works great. There is a video on youtube with step by step instructions for the 2g phone. In the vid he mention he does it for 3g phones as well. Here is the link
[ame=http://www.youtube.com/watch?v=fr0arX22in0]YouTube - How to Activate MMS on the iPhone 2G for AT&T or T-Mobile[/ame]