Activate MMS On Your iPhone. No Jailbreak Necessary ( Mac

What do you need:

• iPhone 3G or iPhone 3GS. MMS doesn’t work on earlier iPhones
• iTunes 8.2 or 9.0
• OS X’s Terminal app
• This AT&T Carrier Settings file

How to do it:

1. First thing you need to do is to quit iTunes and open Terminal ( Applications > Utilities ). Type the following command: defaults write com.apple.iTunes carrier-testing -bool TRUE

2.Next you have to update your iPhone with a new carrier settings file, which allows you to change the iPhone’s Network settings and enable MMS.
Right click and save this ATT_US.ipcc carrier settings file to your hard drive. I downloaded it to the default Downloads folder. When it has finished downloading, follow these steps:

• Restart iTunes
• Make sure your iPhone is plugged in
• Select your iPhone under Devices in the left-hand sidebar of iTunes
• Option-Click the “Check for Update” button in the iTunes main window

3. After Option-Clicking the “Check fro Update” button, you need to find the downloaded ATT_US.ipcc file:

• Browse to your Downloads folder and select the ATT_US.ipcc file
• Click on the file and hit “Choose”
• iTunes will copying the new settings to your iPhone
• Unplug your iPhone
• Reboot your iPhone

4. When your iPhone has rebooted, you need to input the following in the Network settings window.Go to Settings>General>Network and choose the new Celullar Data Network option.

5. Then type in the missing username and password. The other settings should already be there. If not, enter them in as follows:

• APN: wap.cingular
• Username: wap@cingulargprs.com
• Password (case sensitive): CINGULAR1
• MMSC: http://mmsc.cingular.com;
• MMS Proxy: 66.209.11.32

5. That’s it , you’re done. Enjoy MMS.

Source