Public Folders have been on the way out ever since Exchange 2007 but there are still organizations that are slow to migration to “better” options (IE, Shared Mailboxes or Sharepoint sites).
Previous processes required migration before moving mailboxes however the Hybrid process will allow the migration of end user mailboxes up to Exchange Online while at the same time providing additional time for moving the data to other options.
The biggest “gotcha” of this scenario requires the configuration of the CAS role to be added to the server hosting the public folder database
The key comment in the Technet blog spelling this out starts with:
The addition of the CAS role will ensure public folder replica referrals happen appropriately if a folder a user is accessing does not have a local replica in the PFDB.
Exchange Online uses RemotePublicFolderMailboxes on the on-premises server with the public folder database in conjunction with the Client Access Server role.
We also need a dedicated mailbox database and mailbox because of how RPC client traffic is relayed thru this role.
In an Exchange 2010 CAS array environment, mailbox databases are stamped with the array name. This won’t work in routing RPC client access traffic properly, thus the separate database.
I had the priviledge of setting this up in an Exchange 2010 hybrid environment and wanted to share a few “gotchas” I encountered.
Let’s take our Mailbox server with the Public folder database, OCEX04