KB Article: http://support.microsoft.com/kb/2640218
You create a new public folder database on a Microsoft Exchange Server 2010 Service Pack 1 (SP1) server. However, the public folder hierarchy is not replicated from other public stores to this new database. Additionally, the following events are logged in the Application log:
Log Name: ApplicationSource: MSExchangeIS Public StoreDate: DateEvent ID: 3079Task Category: Replication ErrorsLevel: ErrorKeywords: ClassicUser: N/AComputer: ComputerDescription:Unexpected replication thread error 0x80070057 on database " First StorageGroup\Public Folder Store (Server_Name)".
Log Name: ApplicationSource: MSExchangeIS Public StoreDate: DateEvent ID: 3089Task Category: Replication ErrorsLevel: WarningKeywords: ClassicUser: N/AComputer: ComputerDescription:Error 0x80070057 occurred while processing an incoming replication message on Public Folder Store " First Storage Group\Public Folder Store (Server_Name)".
Note The events are logged every time when the server tries to backfill the hierarchy.