OK, so I'm going to try to be as specific as possible... Most of my close friends have iPhones (if only I got referral bonuses for selling this many phones ^_^) and they iMessage me. I completed the install of Mountain Lion this morning (Early 2011 Macbook) and turned on Messages. I have never used iChat before - this was a fresh setup, and I'm testing it to see if I want to switch from Adium. I logged into Messages with my Apple ID plus my GMail and Yahoo accounts and asked one of my friend to send me a message from her iPhone. The message came through on my iPhone under the iMessage header and my reply was blue. However, despite the Messages app showing my "iMessage" account as online, I did not receive it in Messages and it didn't pop up in the Notifications window. I do not have terribly fancy setups - I have one Apple ID, my Macbook, one iPhone, one iPad. All three are connected to the internet on the same Wifi network; the iPhone and iPad both have access to AT&T. It's probably a PEBKAC issue; I tried to RTFM but most of the Messages help windows tell me So, here I am. What sorts of settings may be at fault? Thanks .