We recently had three 2016 Exchange servers in a DAG, decommissioned two and left one specifically for internal SMTP relays (for on prem apps that don't support authentication with O365) and user account creation (we sync to the cloud using Azure AD Connect). All of our mailboxes and email flow has been migrated to the cloud.
Everything I'm reading is saying that we do not need an Exchange volume license to run this on prem Exchange server since mailboxes are in the cloud and we operate using E5 licenses, but I can't find any conclusive statement on this from Microsoft.
When I run "get-exchangeserver | format-list name, edition, admindisplay version" from Exchange powershell on the onprem Exchange server, I get the following:
Name : EXCHANGE1
Edition : Coexistence
AdminDisplayVersion : Version 15.1 (Build 2375.7)
Does the "coexistence" edition suffice for licensing, or do we need to use a volume license for our purposes?