It appears there is a way to enable iPhone MMS without upgrading your firmware to version 3.1, according to a report by OS X Daily. You must simply download the carrier file that enables the functionality. AT&T’s update apparently doesn’t require the iPhone OS 3.1 IPSW (update/restore) file from Apple in order to enable MMS on second- and third-generation iPhones.

As most iPhone fanatics should know, MMS works only on iPhone 3G and iPhone 3GS, while the former doesn’t support video MMS. However, iPhone OS 3.1 is not required to enable the multimedia messaging service from AT&T, according to at least one iPhone user.

“After reading all the bad press for iPhone OS 3.1, I decided to hold out on upgrading, which means that I also can’t get MMS working, right? Wrong! The only thing you need to enable MMS on iPhone 3.0 (or 3.01) is the updated carrier file,” a person over at OS X Daily explains, offering up a download via RapidShare. After downloading the “ATT_US.ipcc” carrier file, users must first ensure iTunes is closed and then type the following command in the terminal:

defaults write com.apple.iTunes carrier-testing -bool TRUE

Upon launching iTunes again, users must select their iPhone and employ the selective ‘Restore’ function by holding down the option key as they hit the Restore button. iPhone owners must then navigate to the location of the.ipcc they’ve just downloaded and select it for restoring. “The update will take a few seconds, and then all you need to do is reboot your iPhone for MMS to work with 3.0,” the author of the guide says.

The poster fails to mention whether or not iPhone OS 3.0 / 3.0.1 users are still eligible for receiving the AT&T carrier file the normal way – by connecting to iTunes and waiting for AT&T to push the update to them. After all, Apple did its MMS-support-bit with the release of iPhone OS 3.0.