I had been sending group imessages in a thread earlier in the day on my iPhone 5 and later when I got my iPhone 6 I received an iMessage in the thread and sent an iMessage back, but when the other person responded it showed up as received from unknown. Once that happened I can still receive iMessages from the other two people in the thread, but I can only send a text back. If I send an iMessage individually to each person everything is fine and as it's always been. It's just the when I send a message in the group. I've tried signing out of iMessage and turning off iMessage and restarting my iPhone. Something I noticed that when I enter the thread it doesn't show "Group" at the top, but says "Outgoing". Nothing seems to work. Any help is greatly appreciated.