I thought I'd post this because it comes up alot and there isn't a single place this information sits(as far as I could found in my searches). Also I have to find them all over again when it comes up. So here it is.
The KB from T-Mobile:
APN settings laid out in the KB: Name: T-Mobile APN: epc.tmobile.com or fast.t-mobile.com (for LTE devices) Proxy: <Not set> Port: <Not set> Username: <Not set> [T-Mobile states for the MT4G/Glacier to enter "None" (without quotes) for this and to NOT leave this as <Not set>] Password: <Not set> Server: <Not set> MMSC: http://mms.msg.eng.t-mobile.com/mms/wapenc MMS proxy: <Not set> MMS port: <Not set> MMS protocol: WAP 2.0 MCC: 310 MNC: 260 Authentication type: <Not set> APN type: default,supl,admin,dun,mms <-- Specified for MT4G otherwise --> <Not Set> OR Internet+MMS (depending on software version)
Some people enter 126.96.36.199 for the MMS Proxy and 8080 for MMS Port I have never had to and am not exactly why these values might be needed but try them if the T-Mobile settings don't work.