Do you have working MMS? If you do, there's a lot of people here that would like to know how you did it without mods.
I do have working MMS and working marketplace and my phone is not unlocked or anything else.
First you need to go to marketplace and download the wireless manager under the samsung zone.
To do that you will need to be on Wi-Fi probably.
Then open Wireless Manager and slide over for APN.
WPSMOBI_APN
Profile: others
APN: wap.cingular.
Auth Type: none
Proxy Address: wireless.cingular.com
Proxy domain: moservices.microsoft.com
proxy port: 80
Internet_line
Profile Category: internet (always on)
APN: att.mvno
Auth Type: none
EVERYTHING ELSE IS BLANK.
MMS:
Profile Category: mms
MMSC:
http://mmsc.cingular.com
APN: att.mvno
Auth Type: none
Proxy Address: 66.209.11.33
Proxy Port: 80
Under Settings go to Cellular:
Edit APN
APN: att.mvno
Everything else blank.