Copied from this thread...............
http://www.blackberryforums.com/show...t=t-mobile+tcp
T-Mobile - Has TCP/IP
Go to Options->TCP (or Tools->TCP)
APN: wap.voicestream.com
Username: (blank)
Password: (blank)
Note: T-Mobile has fixed the port-blocking issue - see this post for more info. In rare cases, it is reported you may need to enter your T-Mobile username and password, the same information used for logging into
www.t-mobile.com/bwc ... If it still does not work properly, just call T-Mobile (call after Feburary 11th, 2005), and ask them to get the "wap.voicestream.com Internet Access Point Name" added to your BlackBerry account at no extra charge.