During a migration from Exchange Server 2007 to Exchange Server 2010 you may encounter a problem with the replication of public folders.
In this situation neither the public folder hierarchy or content will replicate from Exchange Server 2007 to a public folder database on Exchange Server 2010. This will usually occur in Exchange organizations that have previously run versions of Exchange Server 2003 or below.
The Exchange Server 2010 Application Event Log will have this error:
Log Name: Application
Source: MSExchange Store Driver
Date: 13/06/2010 2:08:36 PM
Event ID: 1020
Task Category: MSExchangeStoreDriver
The store driver couldn't deliver the public folder replication message "Status Request (PublicFolders@domain.com)" because the following error occurred: The Active Directory user wasn't found..
The cause of this error is a legacy container in Active Directory for the Exchange 2003 (or earlier) server objects.
Note: this only applies to organizations that no longer run any Exchange 2003 or earlier servers. Do not follow these steps if you still have Exchange 2003 or earlier versions running in your organization.
Launch ADSIEdit.msc and navigate to CN=Configuration <your domain>, CN=Services, CN=Microsoft Exchange, CN=<your org name>, CN=Administrative Groups, CN=<your legacy administrative group>, CN=Servers.
If you no longer operate any Exchange 2003 or earlier servers and the Servers container is empty then you can delete the container.
You should now be able to replicate the public folder hierarchy and content from Exchange Server 2007 to 2010.