Also try an app in the App Store called Send mms. It does exactly what you want it to do. It sends sms and mms message from your email to messages. It does all the hard work of putting in the codes or whatever you just put in the phone number and tell them what carrier the person is on and it is done. You can go to your mail to see that it was sent. I use it all the time even though I have regular messaging. You can do more with it. And you can write longer messages.