When an Exchange 2000 server joins an existing Microsoft Exchange Server 5.5 organization, the public folder Access Control Lists (ACLs) may lose some Access Control Entries (ACEs).
An event ID 9551 message that is similar to the following may also be logged in Event Viewer:
Event Type: Warning
Event Source: MSExchangeIS Public Store
Event Category: General
Event ID: 9551
Date: 2001-03-29
Time: 08:31:33
User: N/A
Computer: Exchange Server
Description:
An error occurred while upgrading the ACL on folder [Public Folders]/PF located on database "First Storage Group\Public Folder Store (Exchange Server)".
The Information Store was unable to convert the security for /O=Org/OU=Site/CN=RECIPIENTS/CN=DL into a Windows 2000 Security Identifier. It is possible that this is caused by latency in the Active Directory Service, if so, wait until the user record is replicated to the Active Directory and attempt to access the folder (it will be upgraded in place). If the specified object does NOT get replicated to the Active Directory, use the Microsoft Exchange System Manager or the Exchange Client to update the ACL on the folder manually.
The access rights in the ACE for this DN were 0x41b.