~via BB (wap.pinstack.com)~
There is a known issue with MMS between T-Mobile and other carriers. I don't know for sure, but I think it is something on their side. There isn't any "fix" that you can do yourself. There is a work around though. MMS can be sent like an email. Have them send it to your BB email address, and are if that doesn't work. That's how I got around the problem.