Read this section carefully to obtain a full understanding of why you should avoid changing permissions through PFDAVAdmin when you are seeing event 9551 in your environment.
When a public folder replicates over to Exchange 2000 Server or Exchange Server 2003 from Exchange Server version 5.5, the permissions from Exchange Server 5.5 are stored in ptagACLData, which is the legacy ACL that has permissions based on legacyExchangeDN. When a client on Exchange 2000 Server tries to access a public folder, a new SID-based ACL is used - ptagNTSD. When ptagACLData contains permissions, Exchange 2000 Server must query Active Directory for each legacyExchangeDN listed in ptagACLData, and get the SIDs for those users so it can move the permissions into ptagNTSD. When it cannot find a legacyExchangeDN, an event 9551 is generated and the permissions from ptagACLData cannot be upgraded.
This situation results in ptagACLData containing permissions that are not visible in ptagNTSD. By default, when a single legacyExchangeDN from ptagACLData cannot be found, the store does not promote any of the permissions to ptagNTSD except entries with Owner permissions (if their domain names can be resolved).
PFDAVAdmin views and directly modifies ptagNTSD. When you use a tool such as Exchange System Manager (ESM) or Microsoft Office Outlook®, both of which change the permissions through MAPI, you will see the legacy ptagACLData information. In PFDAVAdmin, you see only what ptagNTSD actually contains. If a user cannot access a folder, and you suspect that the ACL upgrade has failed, using PFDAVAdmin is an easy way to see what ptagNTSD contains, which is who actually has permissions to access the public folder that is stored on Exchange 2000 Server or Exchange Server 2003. If you can see their permissions on the folder in ESM, but not in PFDAVAdmin, and in PFDAVAdmin you can only see Owners on the folder, the ACL upgrade has failed.
You cannot completely correct a failed ACL upgrade through PFDAVAdmin. For the ACL to upgrade, the store must be either able to find legacyExchangeDN in Active Directory or must be told to ignore domain names that it cannot find (for example, by using the Ignore Zombie Users registry value).
If you edit an ACL in this state in PFDAVAdmin, the legacy ACL information will be lost. If you are not concerned with the old permissions, you should still be cautious making any ACL changes in PFDAVAdmin when you see event 9551 in your environment. This caution includes using Fix Folder DACLs and Propagate Folder ACEs. Running either of these options will definitely “correct” any event 9551 messages. However, it will do so by eliminating the legacy ACL information that did not upgrade.
Conversely, any operation that causes ptagNTSD to be evaluated triggers an attempt to upgrade ptagACLData. Running Export Permissions from PFDAVAdmin is a good way to “touch” all the public folders and cause the store to immediately attempt an ACL upgrade, which will reveal any event 9551 problems. Because running an export only reads the permissions and does not modify them, any permissions that fail to upgrade remain in ptagACLData.
For more information about how to work with event 9551, search the Microsoft Knowledge Base (http://go.microsoft.com/fwlink/?linkid=31845) and use 9551 as your search query. An example of one of the many Knowledge Base articles is 328880, "How to troubleshoot public folder performance issues that are related to ACL conversions in Exchange 2000 and in Exchange 2003" (http://go.microsoft.com/fwlink/?linkid=3052&kbid=328880).