We wanted to let you know about a problem that can cause some or all of the replicas of a public folder to unexpectedly disappear when changing the replica lists on Exchange 2010. This can happen when using the Exchange 2010 RTM (Released to Manufacturing) Public Folder Management Console, the Set-PublicFolder cmdlet (or scripts that call it) or the ExFolders tool connected to Exchange 2010 RTM server. If only some of the replicas disappear, you may try to add them back, only to see them instantly vanish again. If all of the replicas disappear, you must restore the public folder data from a backup.
This is due to a bug in the Information Store in Exchange 2010 RTM. When Store receives the new replica list from the admin tools, under certain conditions it makes the wrong decision about which replicas are supposed to be added and which are supposed to be removed. This bug has been fixed in Exchange 2010 Service Pack 1 (SP1) Store.
This behavior will only affect folders that were originally created when Exchange 5.5 was present in the environment, so you typically only see this on very old public folders.
It is not possible to accurately predict whether a public folder will be affected by this bug, aside from ruling out folders that were created after Exchange 5.5 was removed (as those will not be impacted). Because the consequences of the bug can be severe, if you had Exchange 5.5 in your organization at some point in the past, we recommend that you do not manage public folder replicas on or connected to an Exchange 2010 RTM server if you can avoid it. Managing public folder replicas with either "legacy" management tools (Exchange 2003 or 2007), Exchange 2010 SP1 management tools or any other public folder management interface connected to Exchange 2010 SP1 server is safe.
A quick summary of the issue and resolution, so there are no misunderstandings:
You could run into this problem if:
You have public folders that were created when Exchange 5.5 was in your organization.
You use Exchange 2010 RTM management tools (or any other management tools connected to an Exchange 2010 RTM server) to make replica changes of those "old" folders.
You will not run into this problem if:
You do not have any public folders created when Exchange 5.5 was in your organization.
You use either Exchange 2010 SP1, Exchange 2007 or Exchange 2003 management tools (or any other management tools connected to an Exchange 2010 SP1, Exchange 2007 or Exchange 2003 server) to make replica changes of those "old" folders.
You already used Exchange 2007 RTM management tools to manage replicas of specific folders; if you did not have a problem managing those folders, you will not have it in the future either.