A while back, I sent a text message and got this error back from AT&T.
Wow... thanks. I... didn't know you cared?
Apparently they just append the text of the message (this one was to my wife) to the end of the error, without saying "original message follows" or anything like that.
In case anyone wants to try getting their own amusing messages, I believe this happened because I mistakenly sent to a land line.