IPhone 4S won't send pictures to non iphone users?

I just bought an unlocked iPhone 4S from the apple store. I have tmobile. SMS is turned on so I can text non iphone users, however my phone will not let me send them pictures. It will just say "sending failed" with a red exclamation mark on the iMessage icon. I can send and receive pictures to and from iPhone users and I can send and receive normal texts from anyone regardless of phone or carrier. However, I cannot send pictures to non iphone users no matter what I try. Picture messages should not be blocked on my data plan because everything worked just fine on my old Motorola and I didn't change my plan and I have an unlimited plan. Can anyone help? Please and thank you!

In almost all cases they most likely if you had an unlimited data plan before they wouldve migrated you to an unlimited iphone data plan. Thats how AT&T and Verizon are when going from non-iphone to an iphone. Please call T-Mobile to have their tech team investigate why you cannot send pictures to and from non iphone users. Had nothing to do with your phone, its your service.

I own an iPhone 4S and have had similar problems. Depending on what model you are sending to, it may not send if that person does not have pix messages on their plan. Also, for some reason a pix message will not send as long as your data is off. I know this may not be helpful, but if you need any specific information feel free to comment on my page!

My friend just switched from an Android phone to an IPhone 4S. I'm on a Samsung 4S.
We used to be able to send and receive MMS texts with no problem, but now we can't. Is this because of the difference in the phones? We have different carriers, nut they're still the ones we used before.
Any insight?