Nevermind, I got it.
Here's the correct APN settings for anyone who is interested:
The official T-mobile configuration settings are as follows:
Instructions:
To set up Internet and picture messaging on your device, follow these steps:
Internet setup
From the main screen, scroll to and select Settings.
Select General, Network.
Verify that Data Roaming is set to On.
3G Enable is Off
Select Cellular Data Network.
Note: In software versions prior to 2.0, Cellular Data Network is called EDGE.
In the APN field, enter epc.tmobile.com.
Leave the Username and Password fields blank.
Press the Home button to save the APN and exit to the main screen.
Select Settings.
Select Wi-Fi.
Select off.
Test the connection by opening the Safari Web browser.
Picture messaging (MMS) setup
From the main screen, select Settings.
Select General, Network.
Select Cellular Data Network.
¿ Note: In software versions prior to 2.0, Cellular Data Network is called EDGE.
In the MMS section, enter epc.tmobile.com in the APN field.
Leave the Username and Password fields blank.
In the MMSC field, enter mms.msg.eng.t-mobile.com/mms/wapenc.
Leave the MMS Proxy, MMS Max Message Size, and MMS UA Prof URL fields blank.
Press the Home button to return to the main screen.
Turn the device off and back on.
From the main screen, select Settings.
Select Messages, MMS.
Verify that MMS Messaging is set to On.
Test the settings by sending a picture message to your own mobile number.
NOTE: The handset must be turned off and then back on following MMS configuration. Until this is done you will not see an option to send an MMS.
Verify MMS is enabled:
Tap Settings
Tap Messages
Tap MMS
Set MMS Messaging to On
Send a Picture Message:
Create a new Text Message
There will be a Camera icon on the screen.
Tap the Camera icon to add a Picture to the Message.