On-Premises Legacy Public Folder Coexistence for Exchange 2013 Cumulative Update 7 and Beyond

What are we talking about today?

In Exchange 2013 CU5 (yes 5, V, cinco, fem, and cinque) we started implementing changes to how Legacy Public Folder endpoint discovery will be performed by Outlook (for Windows) in the future. This work continues behind the scenes and will be completed with the release of Cumulative Update 7. This becomes important in on-premises Exchange coexistence environments where some or all of your on-premises user mailboxes have been moved to Exchange 2013 and your Public Folder infrastructure is still on Exchange 2007 or Exchange 2010. Anyone whom has gone through the Legacy Public Folder hybrid configuration steps for Exchange Online will recognize what we are about to go through for the on-premises edition of Exchange 2013.

Why should I care about this?

Prior to CU7, Exchange 2013 mailboxes using the Outlook client were proxied to the legacy mailbox server hosting the Public Folder being accessed either via RPC/TCP or RPC/HTTP depending on the client’s location, the connectivity model being used, and the configuration on the legacy Exchange servers.

With the introduction of MAPI/HTTP in Exchange 2013 SP1, we identified an issue where clients could not always access the legacy Public Folder environment after moving to the MAPI/HTTP protocol.

An analysis of this behavior led us to understand that a combination of RPC Client Access code and older code within the Outlook client enabled the client to be redirected to the legacy Public Folder store under certain circumstances. While you may be thinking this is great news, it is not the desired state – both Exchange and Outlook need to utilize a common pathway for directing clients to connect to mailbox and Public Folder data. That common pathway is Autodiscover.

In the future, both Exchange and Outlook will remove the old code that enabled the older redirection logic. As a result new configuration steps exist which customers should undertake to coexist with legacy Public Folders and support connectivity with Outlook (for Windows) clients whose mailboxes reside on Exchange 2013, regardless of the connectivity protocol (RPC/HTTP or MAPI/HTTP) in use by their clients.

We are providing you with this information in advance of CU7’s release (No, we’re not going to answer when it will be released other than ‘when it is ready.’J) so you may prepare your environments for the new legacy public folder coexistence method. All of the commands discussed here were available starting in CU5 so you may configure your environment in advance of deploying CU7 if you would like to.

Read the complete blog at https://blogs.technet.com/b/exchange/archive/2014/11/07/on-premises-legacy-public-folder-coexistence-for-exchange-2013-cumulative-update-7-and-beyond.aspx

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