To perform Exchange Server 2010 decommission follow the below procedure, the account you use must be delegated membership in the Exchange Full Administrator role on Exchange Servers.
- Move all legacy Exchange 2010 mailboxes to newly deployed Exchange server 2013/2016 in the organization.
- Move all content from the public folder database on the Exchange 2010 server to a public folder database on an Exchange 2013/2016 server in the organization.
- Remove all replicas of PFs on the 2010 side using 2010 management tools so that all PFs in the 2010 hierarchy have only one replica. This should be do able even though you migrated the PFs to 2013/2016.
- Remove the public folder mailbox and stores on the Exchange 2010 server
- On Exchange 2010 servers, for each offline address book (OAB), move the generation process to an Exchange 2013/2016 server. Ensure 2013/2016 is the one generating/serving OABs for users.
- Remove all added DB copies of mailbox DBs so each DB has a single copy in Exchange Server 2010.
- Remove all nodes from any existing Exchange Server 2010 Database Availability Group
- Delete the Exchange Server 2010 Database Availability Group
- Optional: Set the RpcClientAccessServer value of all 2010 DBs to the FQDN of their server
- Optional: Remove the CAS Array Object(s)
- Check the SMTP logs to see if any outside systems are still sending SMTP traffic to the servers via hard coded names.
- Start removing mailbox databases to ensure no arbitration mailboxes still exist on Exchange 2010 servers
- Verify that Internet mail flow is configured to route through your Exchange 2013/2016 transport servers
- Verify that all inbound protocol services (Microsoft Exchange ActiveSync, Microsoft Office Outlook Web App, Outlook Anywhere, POP3, IMAP4, Auto discover service, and any other Exchange Web service) are configured for Exchange 2013/2016.
- Start uninstalling Exchange Server 2010 and reboot the server.