Hi everyone. I'm also asking this elsewhere in case I don't receive a response here. It has recently come to my attention that I cannot send messages using the Messages app on my mid-2013 MacBook Air. I can only receive them. I know this because just this week I asked my neighbor across the hall to try and send me something. He did, and I was notified of it yesterday when I returned from a work-related outing. I asked a friend and coworker if I could try sending him a message, and I did that just this morning. The only way I can send text and voice messages is if I send them to myself, which is rather pointless. Anybody else experiencing this issue? I have the latest build of OS Sierra.