On one of my tests I was trying to add Hub role to a server that already had Mailbox role installed. When I started the setup, I got an error and pre-requisite check failed with error “Setup cannot use domain controller ‘dc1.mytest.int’ because an override is set in the registry.”

I then tried to run setup with “/domaincontroller dc2.mytest.int” which failed with same error as well.

It was interesting. What could be causing this issue? I remembered that few minutes ago I had run command:

Set-ExchangeServer -Identity exch1 -StaticExcludedDomainControllers dc1.mytest.int

I was trying to have my Exchange servers only connect to only one out of two Domain Controllers I had setup. I tried to reverse this by running:

Set-ExchangeServer -Identity exch1 -StaticExcludedDomainControllers $null

I ran the setup again and it still failed with same error!

After doing some research I found out that when I created exclusion, a registry entry was created for “ConfigDCHostName” at:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\ Services\MSExchangeADAccess\Instance0

The entry had no value assigned. I deleted the “ConfigDCHostName” entry and gave setup another try.

Setup worked without any issues this time!

Quote of the day:

It is a mistake to think you can solve any major problems just with potatoes. – Douglas Adams