[Tim]

Here's settings I found on T-Mobile's Wireless Data Configurator Website for T-Mobile t-zones, T-MobileWeb, MMS, and T-Mobile Internet. This tutorial is specifically designed for the T-Mobile MDA, but it should work on other (unlocked) Windows Mobile 5.0 Phone Edition devices as well.

T-Mobile t-zones and T-MobileWeb:

Want to browse Web sites, check the weather, and get directions on your phone? Use these settings to set up Internet access on your phone using t-zones and T-MobileWeb. You can then further configure your device using My T-Mobile to take advantage of all the additional features that t-zones provides.

EDIT: You can also try this before trying setting up your settings manually follow this link to see what cab. you need to download and install and full instructions.
(NEW) Update 06/29/07 T-mobile US GPRS & 600k MMS cab - xda-developers


Setting up the handset

1. Tap Start.
2. Tap Settings.
3. Tap on the Connections tab.
4. Tap the Connections icon.
5. Tap Add a new modem connection under T-Mobile GPRS.
6. Enter T-Zones in the Enter a name for the connection field.
7. Tap to select Cellular Line (GPRS) from the Select a modem drop down list.
8. Tap Next.
9. Enter wap.voicestream.com in the Access point name field.
10. Tap Next.
11. Tap Finish.
12. Tap Edit my proxy server under T-Mobile GPRS.
13. Tap to check This network connects to the Internet.
14. Tap to check This network uses a proxy server to connect to the Internet.
15. Enter 216.155.165.050 in the Proxy server field.
16. Tap Advanced.
17. Tap HTTP.
18. Enter 8080 in the Port field.
19. Tap OK four times.
20. Tap Start again.
21. Tap Internet Explorer.
22. Browse to T-Mobile: t-zones home.
23. Tap Menu.
24. Tap Tools and tap Options.
25. Tap Use Current under Home page.
26. Tap OK.

The new WAP profile is now configured and ready for use.
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T-Mobile MMS Settings:
Setting up the data account

1. Tap Start.
2. Tap Settings.
3. Tap on the Connections tab.
4. Tap the Connections icon.
5. Tap Add a new modem connection under T-Mobile GPRS.
6. Enter PictureMessaging in the Enter a name for the connection field.
7. Tap to select Cellular Line (GPRS) from the Select a modem drop down list.
8. Tap Next.
9. Enter wap.voicestream.com in the Access point name field.
10. Tap Next.
11. Tap Finish.

Setting up the MMS profile

1. Tap Start again.
2. Tap Messaging.
3. Tap Menu.
4. Tap MMS Configuration.
5. Tap the Servers tab.
6. Tap New.
7. Enter PictureMessaging in the Server Name field.
8. Enter 216.155.165.050 in the Gateway field.
9. Enter 8080 in the Port number field.
10. Enter http://216.155.174.84/servlets/mms in the Server address field.
11. Tap to select T-Mobile GPRS from the Connect via drop down list.
12. Tap to select WAP 2.0 from the WAP Version dropdown.
13. Tap OK.
14. Scroll to PictureMessaging and tap Set As Default.
15. Tap OK.

The new MMS profile is now configured and ready for use.

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Use Your Phone As A Modem

T-Mobile Internet (standard Internet connections using your mobile phone and laptop computer or PDA):
Setting up the handset

1. Tap Start.
2. Tap Settings.
3. Tap on the Connections tab.
4. Tap the Connections icon.
5. Tap Add a new modem connection under T-Mobile GPRS.
6. Enter T-Mobile Internet in the Enter a name for the connection field.
7. Tap to select Cellular Line (GPRS) from the Select a modem drop down list.
8. Tap Next.
9. Enter internet2.voicestream.com in the Access point name field.
10. Tap Next.
11. Tap Finish.

The new Internet profile is now configured and ready for use.
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T-Mobile VPN (you wish to connect to your company's VPN and therefore require a static IP address):
Setting up the handset

1. Tap Start.
2. Tap Settings.
3. Tap on the Connections tab.
4. Tap the Connections icon.
5. Tap Add a new modem connection under T-Mobile GPRS.
6. Enter T-Mobile VPN in the Enter a name for the connection field.
7. Tap to select Cellular Line (GPRS) from the Select a modem drop down list.
8. Tap Next.
9. Enter internet3.voicestream.com in the Access point name field.
10. Tap Next.
11. Tap Finish.

The new Internet profile is now configured and ready for use.