I figured I'd post about how to get MMS messaging to work on iPhone 3.0 for those that cannot get it to work (already mailed this to the admins). First of all, one has to upload the hacked/custom AT&T .ipcc file (requires beta iTunes, etc.). It's up to you to obtain this stuff (...torrents?). Sometimes it works after you do this and continues working. Sometimes it works for a bit until AT&T's network detects you using MMS/tethering and turns it off for your account. If it does not work/stops working, one should call AT&T customer service and tell them your text messaging doesn't work, and ask to be put on a "standard text messaging plan" instead of an iPhone specific one (they will try to give you an iPhone specific text messaging plan, which blocks MMS). Tell them you're a developer or something and you need to test your apps with text & MMS messaging. Once that's enabled, assuming you have the proper settings in the Network portion of the Settings on the iPhone (see photos), MMS messages will work instantly. I didn't need to reboot the phone, and in fact I called 611 on the phone and as soon as the customer service agent enabled it, I was able to send an MMS to myself and receive one from her through the AT&T system. Win!