KB Article: http://support.microsoft.com/kb/2640218

INTRODUCTION

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: Application

Source: MSExchangeIS Public Store

Date: Date

Event ID: 3079

Task Category: Replication Errors

Level: Error

Keywords: Classic

User: N/A

Computer: Computer

Description:

Unexpected replication thread error 0x80070057 on database " First Storage
Group\Public Folder Store (Server_Name)".

Log Name: Application

Source: MSExchangeIS Public Store

Date: Date

Event ID: 3089

Task Category: Replication Errors

Level: Warning

Keywords: Classic

User: N/A

Computer: Computer

Description:

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.