You can find the MMS settings for the T-Mobile network in the US listed down below. These are for a Galaxy Note 4 however the MMS settings will work on any mobile phone on the T-Mobile network. Note also that the APN settings for T-Mobile is also listed on this website here. You can follow the instructions below and also see the APN settings elsewhere on this website. If these settings don’t work then contact T-Mobile for more assistance.
T-Mobile MMS Settings : Galaxy Note 4
Settings > Mobile network settings > Access point names
Enter name: T-Mobile
Keep default values for all blank fields shown above.
Press menu button (top right) and select Save. Done.