This is form the AT&T forums, give it a try for what ever reason it hasn't worked for me but but many at the AT&T forums says it works for them:
Using an HTC s620 (unlocked Tmobile Dash) on AT&T’s network
Proxy Settings
Start>Settings>Connections>Proxy> Menu>Add
Description: AT&T WAP
Connects from: The Internet
Connects to: WAP network
Proxy (name: port): wireless.cingular.com:80
Type: HTTP
Username: (leave blank)
Password: (leave blank)
GPRS Connections
Start>Settings>Connections>GPRS>Menu>Add
Description: AT&T IMS
Connects to: The Internet
Access point: ims.cingular
User name: (leave blank)
Password: (leave blank)
Authentication Type: None
Primary DNS: (leave blank...will later default to 0.0.0.0)
Secondary DNS: (leave blank...will later default to 0.0.0.0)
IP address: (blank)
Start>Settings>Connections>GPRS>Menu>Add
Description: MEdia Net
Connects to: The Internet
Access point: wap.cingular
User name:
WAP@CINGULARGPRS.COM
Password: CINGULAR1
Authentication Type: CHAP
Primary DNS: (leave blank...will later default to 0.0.0.0)
Secondary DNS: (leave blank...will later default to 0.0.0.0)
IP address: (blank)
Advanced Connections Settings
Start>Settings>Connections>Menu>Advanced
Internet Connection: Automatic
Work Connection: Automatic
WAP Connection: Automatic
Secure WAP Connection: Automatic
Open Internet Explorer,
Menu>Tools>Options>Connections
Auto Detect Settings: Unchecked
Select Network: The Internet
MMS SETUP
(Text/Multimedia), Menu, New, MMS, Menu, Options, Message Options, Menu, MMSC Settings, Menu, New
o Name: Cingular MMS
o MMSC URL:
http://mmsc.cingular.com
o WAP Gateway: wireless.cingular.com
o Port: 80
o Connect Via: The Internet
o Max. Sending Size: 300K
o WAP Version: WAP 2.0
Click Done
Menu>Set as Default
Click Done to return to the MMS Preferences Screen
Check the following boxes:
- Automatic download in home & roaming network
- Save sent messages
- Allow delivery report
- Allow read report
No. of Attempts: 3
Photo Resolution: Original Resolution
Click DONE
Forward Message