I'm not able to iMessage my wife via her mobile number. She can iMessage me via my mobile number and my Apple ID email address without any issues. I'm able to iMessage her at her Apple ID email address only. She is on iOS 6 and I am on iOS 5. We are both on the same carrier in Japan and our phone numbers are entered in +81...format. I've actually also tried dropping the "+81", but still does not work. I've been trying to figure this out for a while and can't seem to fix it, so any suggestions would be much appreciate.