I've had my iPhone 4S for about two months. Up until last week, I had no trouble sending picture messages to all of my contacts. Last week, all of a sudden, picture messages to my boyfriend's phone started coming up with a "message send failure" error. I can still send pictures to all of my other contacts.
He has an iPhone 4, on AT&T. I can still receive pictures from him. I've tried all the fixes I've seen recommended online. MMS is turned on, and the issue persists whether I'm on Wifi or Cellular. I tried relaunching the messaging app, restarting the phone and pulling out the sim card.
What to do?
No thanks to anyone at Best Buy or Verizon tech support, but I did finally figure out what was wrong. I had added my boyfriend's work number to my contacts entry for him, and for some reason the phone was defaulting to that for picture messages but not text messages.