It would appear that the Exchange 2010 EMC isn’t particularly bright; when you launch it, it picks a CAS to connect to from AD. This is fine.
However, should that server cease to exist, by which I mean Exchange is uninstalled and it is properly decommissioned, then the EMC will continue to try and connect to it. Even after the connection fails, it’ll keep on merrily plugging away at the non-existent server, never considering that there are probably other servers it could try.
This is very annoying and seemingly very stupid behaviour. To work around it, close the EMC, fire up your registry editor of choice, locate the following key:
HKCU\Software\Microsoft\Exchangeserver\v14\AdminTools\ and delete the
NodeStructureSettings value. This will reset the EMC and cause it to pick a new CAS to connect to; it may also affect other settings that you’ve changed in the console.
Another option is to close the EMC, navigate to
C:\users\<username>\AppData\Roaming\Microsoft\MMC\ and delete the
Exchange Management Console file. This will also reset the EMC and will definitely reset any customisations you’ve made to the console.
Why you should ever have to do this is something of a mystery to me, perhaps Microsoft just never expected anyone to decommission an Exchange server once it was built.