how to add new recipient for Messages on iMac
How do I add somebody from my Contacts list onto my Messages list? The Messages Help says to just type in the telephone number or the email and then type a message. But this does not work for me. I am running Messages 7.0.1 on an iMac (and a MacbookPro), OS 10.8.3. Right now I have just one person I can send messages to, my son, who is listed in the box at the left of the Messages screen. I can send and receive messages with him, so I know I have a valid Messages account that can work. I want to send messages to my wife, on her iPhone or her iMac. She is listed in my Contacts. But Messages does not recognize her phone number (for her iPhone) nor her email. What am I doing wrong? I do not find any mention of this in the Support listing.
iMac (27-inch Mid 2011), Mac OS X (10.6.8)