When using One Identity Quick Connect Exchange Resource Forests (ERFM) and Microsoft Exchange 2013 with PowerShell Remoting enabled, you can encounter the following error:
This can be caused by the LDAP server actually being unavailable or by having the domain configured in ActiveRoles Server to use the service account for domain access.
When the domain is configured to use the service account for domain access, the Exchange cmdlet Enable-Mailbox does not get run correctly due to the requirement of the -LinkedCredential parameter. When set to use the service account, ActiveRoles Server has no username or password to provide for the parameter so the cmdlet fails authentication to the linked domain controller.
Modify the domain configuration in ActiveRoles Server to use an override account instead of the service account. Note that you can use the same account as the service account, however it simply needs to be provided in the override account configuration.
Once configured, the command should work properly as it now has access to credentials on the linked domain.