The Exchange Management Console isn’t very intuitive when it comes to decommissioning servers in your environment. If you’ve opened the EMC and it last connected to a server that you then subsequently decommission, it will try to reconnect to that server the next time you open it, and fail.
Fortunately this issue seems to be limited to the user profile. To resolve this, close the EMC, then open the registry editor and navigate to HKCUSoftwareMicrosoftExchangeserverv14AdminTools
and remove the
Reopen EMC and it will search for another Exchange server to connect to.