3.1 beta 3 is fully capable with carrier file 4.5 to send MMS messages.
Without any hacks or any type of mods, my beta 3 let me send ONE, yes, ONE, MMS message/picture to my email address. I think as soon as some people started doing so, ATT locked down the system because I tried more, and just got the red exclamation symbol.
It'll be here soon enough.
Lame enough, one of my biggest uses will be to post Flight Control scores to the other 8 people I know that play it. It's getting old posting to FB and talking **** that way.