You got the following error in summary reports for Non-Owner Mailbox Access Reporter:
“Active Directory is inaccessible. The report does not contain accessed mailboxes names.”
This error means that Non-Owner Mailbox Access Reporter could not resolve the mailbox GUIDs on the DC and they may appear in the reports . Usually this occurs if there is a child-root or trust domain configuration issue.
The GUIDs appearing in the report are not the result of NetWrix configuration. It is recommended that you either ignore the error or use the following KB to attempt resolve the GUIDs: