To only pick up the local users on the Exchange server you can use the following LDAP query:
(homeMTA=CN=Microsoft MTA, CN=SERVER,CN=Servers,CN=First Administrative Group,CN=Administrative Groups, CN=Red Earth Software,CN=Microsoft Exchange, CN=Services, CN=Configuration,DC=redearth, DC=com)
The homeMTA string can be found in ADSI Edit by checking the homeMTA property of one of the users on the Exchange server.
To import only the users that match the query, follow the next steps:
Open the Policy Patrol Administration console and navigate to Settings > Users and click on Add.
Select Active Directory and click on Next.
Select Import all users from Active Directory and check the option Use the following query filter.
Enter the query from above and click Finish. Only the local users on the Exchange Server will be imported.