Edge server should be in the perimeter network that means no need add to Domain
Then install the Server roles by using powershell
Open an elevated Windows PowerShell console, and run the following command:
Import-Module ServerManager enter
After installing the Microsoft Exchange 2010 Edge server go to Exchange management shell
Create Subscription file for uploading the HUb transport servers
For creating Edge subscription file go to Exchange powershell Type following
new-EdgeSubscription -Filename “C:\Edgeinfo.xml”
Then copy the edge subscription file to the Hub tyransport server in to C:\Edgeinfo.xml
Then In Hub Transport Server Open Exchnage Management console > Organization Configuration>Hub Transport section.
In the action Pane click new edge subscription >edge subscription wizard
Click browse > Select Active Directory site>selecy default
Browse to the location of the Edge subscription file you copied from the Edge transport server and click Next>Finish
verify synchonization to the Edge transport servers AD LDS and review the application log in Event Viewer on both HUB and Edge transport servers.