Once all mailboxes and Public Folders have been moved over, you are almost ready to start decommissioning your older Exchange 2007 or 2010 server.
However, there are still some small steps that you need to take prior to removing them from the environment.
This section comprises of task related to the post migration steps.
Send connector are used to send e-mails either to the Internet or other messaging systems. When installing Exchange 2013, it will not automatically add the Exchange 2013 transport servers to the list of server allowed to use the send connector.
Prior to removing Exchange 2010, these settings need to be updated so that the Exchange 2013 servers are also part of the SourceTransportServers list:
Set-SendConnector –Identity "Internet" –SourceTransportServers @{Add="EX2013-01"}