If there are no send connectors that are configured to use the server as a source transport server, no MX records pointing at the server, and no DNS aliases for SMTP pointing at the server, then it is likely the server is no longer required for production mail flow.
However, it's possible some internal mail flow is still passing through the server simple due to Exchange using all available routes that exist, and some traffic will still appear in message tracking logs.
So as a precaution, you can pause the transport services on the server and see if that impacts your production mail flow.
Exchange 2013 Client Access servers need to be reviewed in the same way as Exchange 2010 Client Access, by checking IIS logs for user connections.
Exchange 2013 Client Access also performs Frontend Transport functionality, so you should also review the protocol logs on the server for any SMTP connections that might still be occurring.
Exchange 2013 Mailbox servers perform the same transport role as Exchange 2010 Hub Transport servers, so you should review them in the same way by using message tracking log searches to determine if any mail flow is still passing through the server.
Exchange setup will warn you of any decommission steps that you've missed, and block you from proceeding with the uninstall if anything still needs to be addressed.
When you're sure no more email is being processed by the server, you can shut it down for a few days as a final test.The Exchange 2013 Edge Transport server for Not Real University has already been shut down, but it's worth taking a brief look at what steps you should perform to remove an Edge Transport server.The most important thing is to ensure no more mail flow is traversing the server.For Not Real University, the organization is running in coexistence with Exchange Server 2010, 2013, and 2016.The goal is to remove all of the legacy servers, leaving only the Exchange 2016 Mailbox and Edge Transport servers in the environment.It's normal to see some traffic in IIS logs from Power Shell connections, or server-to-server traffic (such as health probes), but as long as no regular users are showing up in the IIS logs on the server you can pretty safely consider it safe to remove.Exchange 2010 Hub Transport servers can be decommissioned when there is no more email routing through the server.Since the Exchange 2010 OAB is not used for Exchange 2013 or later organizations, you can simply remove any Exchange 2010 OABs that still exist.You can also dismount the databases to determine if their removal is going to cause any problems.For DAG members the approach is a little different.The process involves: The uninstall of Exchange from the server can be initiated from the Control Panel, in Programs and Features or Add/Remove Programs, depending on your version of Windows Server.