Updating your Jailbroken iPhone to use MMS. (Using official ATT Carrier settings)
First and foremost make sure you have the latest version of iTunes (9.01).
What you need to do next is go HERE and download the ATT Official Carrier Settings file we’ll need to update. Save this wherever you wish.
MAKE SURE ITUNES IS CLOSED NOW!
Windows 32-Bit
Go to Start>Run type:
cmd
Hit enter
Next type:
cd C:\Program Files\iTunes
Next type:
iTunes.exe /setPrefInt carrier-testing 1
Windows 64-Bit
Go to Start>Run type:
cmd
Hit enter
Next type:
cd C:\Program Files (x86)\iTunes
Next type:
iTunes.exe /setPrefInt carrier-testing 1
(This part applies for both 32-bit and 64-bit versions of Windows)
Now launch iTunes, deny for it to let you update to 3.1 and click on your iPhone in the left hand column. Next HOLD DOWN SHIFT (this is very important) and click UPDATE. For “Files of type:” choose “iPhone Carrier Configuration File (*.ipcc)”. Navigate to where you downloaded the IPCC file I told you to and hit open. It’ll update your carrier file for you. Now unplug your iPhone and reboot it. Now go into messages and go to send a message you should have a camera icon next to the text input line. TADA! You now have MMS capability on your iPhone with 3.0 (or 3.0.1) firmware!
Mac OSX
Run Terminal (Applications>Utilities)
Next type:
defaults write com.apple.iTunes carrier-testing -bool TRUE
Now launch iTunes, deny for it to let you update to 3.1 and click on your iPhone in the left hand column. Next HOLD DOWN OPTION (this is very important) and click UPDATE. For “Files of type:” choose “iPhone Carrier Configuration File (*.ipcc)”. Navigate to where you downloaded the IPCC file I told you to and hit open. It’ll update your carrier file for you. Now unplug your iPhone and reboot it. Now go into messages and go to send a message you should have a camera icon next to the text input line. TADA! You now have MMS capability on your iPhone with 3.0 (or 3.0.1) firmware!
Mind you the difference between this and the other tutorials on how to update your iPhone to use MMS is this is the OFFICIAL IPCC file from ATT that is authorized and signed.