AT&T iPhone MMS Goes Live → Picture Compression

My iPhone updated just fine. Whenever I send pics to another AT&T # the pic is the same. However, when I send a pic to a T-Mobile # the image is blurry and seems to be compressed. Whenever a pic is sent from that same T-Mobile # to my AT&T # their image is received just as it was sent. Is this a T-Mobile or AT&T problem?