What good is the email function in Lightroom 4? It doesn't access the address book on my Mac. You expect me to import my email addresses one at a time? Please, give me back the way it used to be. Who at Adobe could have possibly thought this was a good idea?
If you use native Email client Account(Apple Mail, Outlook, Thunderbird, etc) to send out images: you can edit email body and add 'To', 'From' account in email client app, In this case, you can use system's address book(supported by email client app).
if you use webmail account(gmail, hotmail, yahoo Mail!, or other online email services) to send out images(you have to config your account info): In this case, Lr4 doesn't support the system's address book.