IPhone :: Unable To Receive MMS From Other Phones

Off-topic note: I wasn't sure whether to post this in the Help section or the Hacks section, but I found similar problems in this topic so I decided to post here.Anyway, self-explanatory. I am unable to receive MMS from other phones.I have a iPhone 3gs unlocked (T-mobile).I get the error about message resolution size.I've tried every solution found on forums. The most recent one I've tried is this one http://forums.macrumors.com/showthread.php?t=821026 .

The weird thing is, it used to work before...At default, it didn't work, so I enabled it. Then it didn't work again, so I fixed it...then broke again and so I fixed it one more time. This time it doesn't work at all.And so I've tried a variety of different things found on countless forums. I've also went into Cydia and downloaded the T-Mobile prepaid package or whatever. I tried all 6 of them. And each time I tried new network settings I restarted my phone.Oh and I have 3.0 software. Jailbroken and unlocked. Also, I can receive MMS from other iPhones, but not other phones.Any suggestions? And no I don't remember the settings that I've used when I fixed the problem. But I'm pretty sure I've used them after going through a number of familiar forums with network settings.So in short

-Can send mms to any phones

-Can only receive from iPhones

-Can't receive from phones other than iPhones