I am running MS Exchange 2013 CAS/MDB and an Edge Server in my environment. When I set up the Edge Server I had to run a power-shell command to promote it and join it to the Exchange Server. I am now thinking of going with a different solution for my spam filter such as Proxmox Email Server or Mailcleaner. My question is, do I need to do anything specific to demote the Edge Server? Or can I just install the new appliance and point my firewall to the new mail gateway?