I got this error message while trying to get a delivery report for a message that I had sent before. Luckily, the error message guides you to the solution.
Which searching for a delivery report, the ECP displayed the error below.
Server <serverName> in domain <domainName> encountered an error reading an Active Directory object or attribute. Diagnostic information for this error: DefaultDomain not found in Organization <OrgName>
I had a quick look and confirmed that a default domain existed. But, the issue was that the default accepted domain was not authoritative. It was set as an internal relay. I have seen this happen in Exchange 2003-2010 co-existence environment.
As soon as I changed my default domain to be authoritative, my delivery reports worked fine.
If you are in a scenario where it is not possible to have the default domain as authoritative, you can create a new accepted domain (a dummy one) as authoritative and make that as the default.