I have no affiliation with T-Mobile other than being a customer for several (now, many) years.
These are the two Access Point Name (APN) settings I'm currently (late 2015) using with a Nexus 6 running Android 5.1.1. In an (apparently succesful) attempt to improve Multimedia Messaging Service (MMS) reliability, I've deleted the other default APNs present. This seems to work well for the T-Mobile cellular and Wi-Fi Calling networks both.
APN: T-Mobile GPRS
APN: fast.t-mobile.com
APN type: default,supl
APN protocol: IPv6
APN roaming protocol: IPv4
MMSC: [Not set]
MCC: 310
MNC: 260
APN: TMUS
APN: TMUS
APN type: mms
APN protocol: IPv6
APN roaming protocol: IPv4
MMSC: http://mms.msg.eng.t-mobile.com/mms/wapenc
MCC: 310
MNC: 260
Note: if you have used your Nexus 6 with Google's Project Fi and have lost access to the Cellular network settings interface where APN settings are normally found, you may be able to restore then over USB using the Android Debug Bridge utility, adb:
% adb shell settings put global hide_carrier_network_settings 0
This is a simple (and now rather old) collection of settings for use with the T-Mobile (formerly VoiceStream) U.S.A. network. I have used these settings to configure my own GSM mobile phones and other devices such as PDAs and laptops. They may or may not be accurate at a given time and are compiled here in the hope that others may find them useful.
T-Mobile GPRS/EDGE settings for terminals (e.g., phone handsets). Some items are possibly Nokia-specific. I have found the authentication type can be either Secure or Normal. These settings should be useful for T-MobileWeb users.
APN: wap.voicestream.com
IP address: 216.155.165.050
Data bearer: GPRS
Username: [none]
Password: [none]
Authentication type: Secure
Connection security: Off
APN is the GPRS Access Point Name.
T-Mobile GPRS/EDGE network settings when using a device as a GPRS "modem", that is, when "tethered" to another device. Examples include connection via Dial Up Networking (DUN) Bluetooth profile, or via Universal Serial Bus (USB). These settings should be useful for T-Mobile Internet users.
APN: internet2.voicestream.com
Username: voicestream
Password: [none]
SMTP server: myemail.t-mobile.com
APN is the GPRS Access Point Name.
Users of T-Mobile's Virtual Private Networking (VPN) Internet option should substitute the following APN:
APN: internet3.voicestream.com
T-Mobile ISDN settings for terminals (e.g., phone handsets). This is an ISDN dial-up number for WAP use only. Some items are possibly Nokia-specific. I have found the authentication type can be either Secure or Normal.
Dial-up number: +1 913 244 0821
Data call type: ISDN
Data call speed: 14400
IP address: 10.168.200.50
Data bearer: GSM data
Username: wap
Password: [none]
Authentication type: Secure
Connection security: Off
T-Mobile WAP services (t-zones) settings
Homepage: http://wap.myvoicestream.com
modmyiPhone: T-Mobile settings for the Apple iPhone
Ross Barkman's mobile phone and modem scripts for Mac OS X
T-Mobile GSM Glossary and Definitions
Usenet newsgroup alt.cellular.gsm.carriers.voicestream at Google Groups
GSM network hash codes of interest:
Apparently T-Mobile does not currently support Wireless Transport Layer Security (WTLS) for secure WAP transactions.
T-Mobile made various announcements in 2006 regarding their plans for a U.S. UMTS/HSDPA 3G network upgrade, but as of October, 2007 there is still no 3G service available.
News: Gizmodo reports T-Mobile to announce UMTS, Jessica Alba new T-Mobile spokeswoman.