Why can't I send picture messages with iphone 4?

That little photo icon next to message field is grey and doesn't work when I tap on it. Could it be because of my carrier?

Added (1). Oh and i can't receive pictures too

Settings-Messages and check that SMS and MMS is turned on. If so get ahold of your carrier.picture texts are something the carrier provides so Apple phone support wouldn't be much help.

  • Why won't my iPhone send picture messages? I have an iPhone 4 and every time I try to send pictures it gets to where the sent bar is almost full, then it just stops and won't send. What do I do? I've tried restarting my phone and it didn't do anything. It is on my plan though. I just sent a picture message yesterday but now it's f*cking up.
  • Why won't my iPhone 4s let me send picture messages? It gives me the option to send pictures and will let me choose a photo but when i press sent the little bar at the top fills half way then stops and a little red exclamation mark comes up next to the picture saying not delivered. Is there something wrong with the phone or can a change it my self in the settings?
  • Why do iPhone messages come up as picture messages on other phones? When my friend sends me texts, she has an iphone, they come up as picture messages and i can't revieve them on my phone because my plan doesn't cover picture messages. Can she change the settings so it won't come up as a picture?
  • Why can't I send picture messages with my iPhone to other phones? I can only send picture messages to other people with iPhones but not to anyone that has any other type of phone. I have the 4S and I have my MMS/SMS switch on. What's the problem?