As you would know that Apple doesn’t released MMS feature for iPhone 2G. But jailbreak community can still enjoy it. You still have a chance to enable MMS on iPhone 2G OS 3.1.2 using Native MMS iPhone 2G from Cydia.
Enable MMS on iPhone 2G OS 3.1.2
Use this guide at your own risk. You may also end up restoring your iPhone.
Assuming that you have jailbroken your iPhone and have got Cydia on your SpringBoard.
Open the Cydia, and install iFoneGuide repository. In order to do this go to Search Tab and search for iFoneGuide. Tap on it and Install it.
Once you have install the repository, now search for Native MMS iPhone 2G and install it.
Once the installation is done, go to:
Settings > General > Network
and and input required parameters for your carrier.
That’s it, enjoy MMS on iPhone 2G 3.1.2. This should also be working on OS 3.1 but we have not tested it.