Guys, if you can't get MMS working, listen to me. I followed all these steps in the other posts and had no luck in enabling the sending of MMS. I had the option to send them, but I couldn't actually get them to go through. I've called AT&T multiple times bitching at them to enable MMS and everytime I had a rep tell me they will NOT do it. PERIOD. Okay so... time for Plan B. Do what these other posts are saying and update your carrier file in iTunes to enable the cellular data network area in Settings. I called AT&T's after hours support line about two hours ago and it went like this; (I'm lieing my ass off the whole time to this guy by the way) "I recently sold my iPhone 3G and purchased an unlocked SideKick. I'm having trouble sending and recieving picture messages. It gives me an error whenever I try to send one." He told me how the phone might not be compatible with the AT&T network, but I told him my data was working fine. He assured me that we should be able to get it to work then. The first process we went through was changing the phone on my account from an iPhone. If you've ever been on the AT&T wireless website, it shows your device. This is what we needed to change he said. He asked me for the IMEI number of my phone. You guys are going to need to find someone who has a picture-messaging enabled phone (or probably any T-Mobile phone) and get the IMEI number. This phone ABSOLUTLEY HAS TO be fromT-Mobile so that the IMEI number doesn't match someone else's on AT&T. It will bring up red flags in their system because it will be registered to another account. I gave him the number and he changed it in their system. Then I told him all the blank fields in the MMS category (even though none of them are blank) under CELLULAR DATA NETWORK in the iPhone settings. He then proceeded to tell me things to fill into those fields. He told me some things that didnt match those below, but I just pretended I was listenting to him and used the ones below. APN: wap.cingular Username: firstname.lastname@example.org Password: CINGULAR1 MMSC: mmsc.cingular.com MMS Proxy: 18.104.22.168 He made me try and send MMS's many times during this phone call and after everytime it didn't work, he would try something different in the system. He also had me restart my phone a couple of times. He eventually said, I think I finally got it. He sent me a test picture message of a hamburger (looked delicious) and after about an hour of being on the phone with him.... IT WORKS! I can send/recieve picture messages and contacts without any trouble at all. I really hope this works for you guys. I really think it will. It's a lot of talking and work but if you really want MMS before ****ing LATE SUMMER, give AT&T the middle finger and lie your ass off for about an hour. NOTE: If he mentions anything about changing your internet plan to the PDA-INTERNET package (same price, just for different phones), tell him that your internet works just fine already and to keep the iPhone data package since you plan on buying the 3GS or something.