When trying to install Collaboration Services the following error is returned:
"Unable to enumerate Exchange servers in the forest. Error: 0x80070005 (Access is denied.)"
This can be a result of the Collaboration Services account not having sufficient rights to the Exchange Organization.
In addition, versions of Collaboration Services prior to 2.0.3 had a defect that was resolved in version 2.0.3 and later.
If you are running a version of Collaboration Services prior to 2.0.3 upgrade to the latest version.
Ensure you are running the Collaboration Services installation using the Collaboration Services service account and that the account has the necessary rights to the Exchange Organization:
If you have confirmed that the service account has the required rights to the Exchange Organization and the error is still displayed, explicitly grant Read permissions to the Microsoft Exchange container: