ok i have been trying around to get MMS working on my 3G beta 5 iphone. i have tried numerous ipcc files and MMS settings. i have also called ATT and have my account set on a standard messageing plan instead of the iphone unlimited plan.
does anyone have and tips or tricks? or any advise?
Uuhhhhh yeah.... It works just fine!! It took me many hours (well maybe 2 1/2 hours) to figure it out. First is you have the newest beta of iTunes then you need to downgrade to the beta 4 version. I use a Mac so it's version 8.2b7 (10), as for Windows users can't help you with the version number. Anyways once you have the older version of the pre-release iTunes, download my customized ipcc file. Make sure to make a backup of the current one, but this file needs to be in the same location as the current one. For Mac users the folder is; Users > (USER NAME) > Library > iTunes > iPhone Carrier Support, again can't help you Windows users, sorry

In there is a file named ATT_US.ipcc, copy that file and move it else where. Put my customized ipcc file in the folder and close it out. Next open iTunes and click "Check for Update" while holding the option button, I believe it's the Shift key for Windows, but I don't know. Once the update is done, on your iPhone go to Settings > General> Cellular Data Network, and enter under MMS:
http://mmsc.cingular.com in the MMSC block and 066.209.011.032:80 in the MMS Proxy block, make sure you don't edit anything else!!! Do a soft restart (hold down the home button and the sleep button until it shuts off). Turn it back on and there you go!!! MMS is enabled, and there is no need to call AT&T to activate anything!!! I have the Family Unlimited Plan, with the iPhone Data Package, there is no need to call AT&T, maybe unless you don't share your minutes. Below are links to my images of what it should look like for some reason I cannot upload images on here

I use the Internet Tethering so that is why you see the blue bar

, also the link to the ipcc file is,
http://www.sendspace.com/file/89wg7n
IMAGES:
http://img154.imageshack.us/img154/9074/img0145b.jpg
http://img154.imageshack.us/img154/7156/img0146a.jpg
http://img154.imageshack.us/img154/3849/img0147z.jpg
http://img154.imageshack.us/img154/7985/img0148j.jpg