use swirlymms. if you go here http://www.swirlyspace.com/iPhone/apps/mms/settings.html. you can see all the settings for whatever network you are planning on using. except on att you must have mms on your account and for that to happen you have to have someone at att add it and think you no longer have an iPhone.
BGR reported yesterday that there is an unconfirmed AT&T memo floating around that discussed MMS for the 3G iPhone, or 2.0 software specifically. The OP (iPhone Atlas) goes on to say that it is strange that no text messaging packages have been spotted, and that the original came with 200 texts by default. I know Stevo thinks MMS is a dead tech, but come on, we all want it still! http://www.boygeniusreport.com/