property LookupNS.LastError as String
Retrieves a value that indicates the last error occurred.

TypeDescription
String A string expression that indicates the last error occurred.

If sending the query to a DNS server fails, or the DNS server fails to reply with an answer, the LastError and LastErrorCode properties indicates the error that occurs. The LastErrorCode property gets the code of the last error occurred. 

The list of NS errors is:

Code NS Error Description
32001 The name server was unable to process the query.
32002 The name server was unable to process the query due a problem with the name server.
32003 The host does not exist.
32004 The name server does not support the requested kind of query.
32005 The name server refuses to perform the specified operation for policy reasons

The most frequent error that might appear is 32003 ( The host does not exist.).