I moved my Nexus 5 to T-Mobile and now my MMS isn't working, why?

[AC Question]

Nexus 5 Switch to T-Mobile - MMS Single Threaded

I switched my unlocked Nexus 5 from Straight Talk to T-Mobile yesterday, and I noticed this morning that my MMS messages haven't been working correctly.

When I text to a group I notice that:
- When using the "messages" app (not hangouts) the message gets sent to the thread twice (the group thread I had going from straight talk)
- My friends (iphone users) report receiving the messages 1:1 from me (not a group thread)
- In hangouts the message goes out once to the group, but then gets to them as 1:1 and the responses come from them 1:1

Anyone know how to get this to work with t-mobile?

 

[Almeuit]

Re: Nexus 5 Switch to T-Mobile - MMS Single Threaded

Ensure your APN settings are set to T-Mobile's.