messages not being received by one contact
I have one contact that cannot receive my messages I have sent. We both have the iPhone 4s.
When I do try to send a message to him, it shows up 'blue' and no error message is received. My phone recognizes that it is an iMesssage in the message body but he does not ever receive them. When he sends a message to me, I do receive it but it is a regular SMS in green. I have even tried to simply respond to the messages he sends me, they also show up blue, but he doesn't recieve those either.
We both have iMessage 'on', and both are running 3G
I do not have this issue with any other contacts, iPhone user or not
Thanks for any help.
iPhone 4S, iOS 6