ManageEngine Exchange Reporter Plus license is based on the number of mailboxes. You need to buy a license corresponding to the number of mailboxes in your Exchange Organization. However, if you require data to be collected from mailboxes present in some servers alone, you can selectively manage those servers using this option.
Data is gathered for reporting only from managed servers.
To Manage Exchange Servers :
To manage all servers in an Exchange Organization, select the "Exchange Organization name" and click "Manage".
To Un-manage Exchange servers :
Select the "Servers" you want to unmange.
To unmanage all servers in an Exchange Organization, select the "Exchange Organization name" and click "UnManage".