Most of the companies around the world who are running Exchange 2003 are moving to 2010, as the 2003 support is ending soon. For medium to large companies, this means co-existing with two versions of Exchange, as a big bang weekend transition is not possible. This is due to the number of users and amount of data that these companies have.
Public folder comes into the limelight during co-existence and number of questions come up around the topic. I received a number of questions from a confused exchange admin which has prompted me to write about it.
1. What happens to the user public folders (IPM_SUBTREE) while co-existing? Can you see the public folder hierarchy from an Exchange 2010 server without actually replicating the data?
Yes, you can. You can see the public folder hierarchy even without doing anything. This means that public folder hierarchy is “send” to all servers which has public folder database (both 2003 & 2010) by default, so that the servers can list the public folder hierarchy to the clients. The folder hierarchy has the list of public folders, it’s permissions and info regarding which server holds the replicas.
If you can’t see the PF hierarchy from a 2010 server, run Update-PublicFolderHierarchy –Server “2010 server” from Exchange Shell.
Should you have to set Exchange 2003 PF database as the PF database for 2010 mailbox database for this to work? No, you can have the 2010 PF being stamped on the 2010 mailbox database and this will still work.
So, what about the contents of the public folders? Can a 2010 mailbox view/access the PF data without replicating to 2010 public folder database? Yes, you can. This works because of public folder referrals. When a public folder data is hosted on a different server than the server to which the Outlook client is connected to, PF referral kicks in and Exchange is able to presents the data to the client.
Does this mean that you don’t have to replicate/move data from Exchange 2003 to 2010? The answer is NO. You have to replicate as the data has to be present in 2010 servers, so that the legacy servers can be decommissioned without any business impact.
This means that you don’t have to wait for PF replication to finish to start your mailbox migration. You can do both in parallel, but note that OWA 2010 can’t connect to legacy public folder servers. You will be able to see the hierarchy in OWA 2010, but not the content.
Hope this clears the confusion, if you were confused in the first place