AT&T MMS in enabled in 3.0B2
I was comparing the differences between the 2.2.1 filesystem and 3.0 beta 2's and saw the carrier.plist had changed between the two. 3.0 added these these lines:
<key>MMS</key>
<dict>
<key>GroupModeEnabled</key>
<false/>
<key>MMSC</key>
<string>http://mmsc.cingular.com</string>
<key>MaxMessageSize</key>
<integer>614400</integer>
<key>MaxRecipients</key>
<integer>10</integer>
<key>MaxVideoBitrate</key>
<integer>131072</integer>
<key>OnWhileRoaming</key>
<true/>
<key>Proxy</key>
<string>wireless.cingular.com:80</string>
</dict>
So that is why video and picture mms is enabled
I know there was already a thread saying someone had AT&T mms working, but I wanted to explain why.