The only .ipcc file that I could get to work with MMS is the one from
http://repo.sinfuliphone.com , this is how I did it and my settings.
1. With my SIM card still in my iPhone 3GS, I added the repo to Cydia and install the "MMS & Tethering Settings" NOT the MMS & Tethering Settings for 2G"
2. Downloaded and reset the network settings.
3. Checked to see if the Cellular Data selectino was there, if not then just reboot
4. Go into Cellular data and put in this information if it isn't there already
Cellular Data
wap.cingular
blank
blank
Visual Voicemail
acds.voicemail
blank
blank
MMS
wap.cingular
blank
blank
http://mmsc.cingular.com
066.209.011.032
614400
http://wap.sonyericsson.com/UAprof/W800iR101.xml
NOTE*- Changing the VVM settings from acds.voicemail to wap.cingular WILL remove the tethering option.
After that check to see if the MMS is enabled in the Messages App and the Tethering option in the Network section. If it is then remove the SIM card, if it's not then reboot again and see if it appears.
5. Remove the SIM card from you're iPhone (3G or 3GS) and place it into another cellphone from AT&T, I used a Motorola RAZR V3. Nothing fancy just the original Razr.
6. Make some calls with it and just leave it for a minute or so on the line.
7. Log into you're AT&T online account and go to Features and change the "iPhone Texting" to the normal "Messaging". (If the phone your using doesn't appear and the iPhone is still there, go ahead and change it yourself and make another call then sign out and sign back in.)
8. After you changed the texting plan, go ahead and google "AT&T Media Net" WITH the SIM card still in the other AT&T phone, not the iPhone. A text will be sent to you're phone, just enter the verification code and thats it.
9. Now I'm now sure if this is needed but I sent a MMS from the RAZR V3 to someone else and they sent me one and it worked on the V3 just fine.
10. Reinsert the SIM card into the iPhone and it should work!
Go ahead and email me at
ericksmailis@gmail.com for any questions, I have a iPhone 3GS jailbroken and I have used it on 3 different iPhone 3G's and it works great! At some point it stopped working on two of the iPhone's but the next day it was working fine, weird?
P.S.
After I got the MMS working from the sinful iPhone repo, I couldn't get the tethering option to work. I removed the ipcc file from the repo and installed the one from help.benm.at, reset the network settings, rebooted the phone and entered the settings again and now MMS AND tethering works!