My friend Andrew (what a cool name), has written an article about the latest change in Exchange 2013, starting with CU11 ( and Exchange 2016 CU1). I have to admit I am not a fan of anchoring for Powershell connections, but will withhold final judgment until after I get a chance to play around more with CU11. See:
Does it include Prime?
And maybe CU9. Haven’t tested that, but nonetheless, it didn’t work before CU9. So why install into an existing forest instead of the recommended DMZ or Workgroup? Edge Roles can do more then just “Edge” stuff. They make great open relay servers within your org, let you leverage Powershell and beat the pants off any IIS/SMTP stack you may be running. By installing into an existing forest as a domain member, you can use your domain creds of course, which is a good thing. If you have the licenses, go for it. The Edge role is right in the Exchange admin’s wheelhouse.
Consider the Edge if you need an open SMTP relay in your org. Options are good.