You open ODBC on a server, click on the tab ‘System DSN’, click on CitrixIMA (For example), click
configure and in the drop down list labelled Server, you find old server names which no longer exist.

Your SQL server is up to date and does not show the old servers listed, so why are the old database servers
listed within the ODBC connection and where do you go to remove them.

The old servers are listed within the servers registry under the below path (Important: Always take a backup of your registry before making changes)

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\MSSQLServer\Client\ConnectTo