I'm no expert on this, just trying to figure it out too. I don't think you can go through your regular email app. I'm guessing, but haven't tested it yet, that this could be done in the portal section (via Updox) of AC. The patient communications in the portal are, I think, a form of "Direct Secure Messaging" AKA "Direct Secure Email". See the Updox blurb here:
http://updox.com/updox-platform/direct/From the noise on that window, maybe you have to sign up for it separately? Still trying to figure out which hoops to jump through myself.