1. Try running a gathering with the most recent date as an option to see if this updates the list of Internal Namespaces.
2. Check to see if there are any objects in Active directory Users & Computers relating to that particular Namespace.
3. Check if this namespace appears in the T_InternalNameSpace table in the Messagestats database.
There are only two ways that this table gets populated: Manually in the console and with the Mailbox gathering (using the namespaces from the SMTP addresses). If this namespace no longer exists, and is found in the T_InternalNameSpace table, then simply delete it from the database using the console (Tools | Manage | Internal Namespace Management) and it will not cause any additional problems. If it reappears after it is deleted, then there is definitely a mailbox that is associated with that Namespace.The Mailbox gathering will add Internal namespaces for all of the SMTP addresses associated to a mailbox. If there are odd ones, chances are it is a mailbox in the organization that has a non Primary SMTP address with the given namespace. For example, there was a person in question who had a Hotmail.com address as a secondary SMTP address and it was added to the database. This was done to supplement the Internal Namespace Distribution List report.
The following sample SQL statement can be run using SQL Query Analyzer to remove the defined elements from the Messagestats database:
DELETE FROM T_InternalNamespaceStats
WHERE ((InternalNameSpaceName = 'QUEST.COM.US')
OR (InternalNameSpaceName = 'QUEST.CO.US')
OR (InternalNameSpaceName = 'QUEST.US')
OR (InternalNameSpaceName = 'QUEST.STATE.OR.US')
OR (InternalNameSpaceName = 'QUESTSOFTWARE.US'))
If the Internal Namespaces are still apart of your Organization we have a Enhancment Request open for that Enhancment ID:TF00169093 that is scheduled to be released in MessageStats 7.2
