Exchange public folders is always a hot topic. It was since public folders were first released a bunch of years back. Nowadays, with the large adoption of Exchange Online the new and very big challenge is to move the public folders to the cloud. I have to say, there are some limitations which may result in bottlenecks during a cloud migration, so what I want to do is to shed some light onto this topic. My experience is that the official Microsoft documentation on this topic is sometimes misunderstood.
A first point to take into consideration is the migration of Exchange public folders to Exchange online in a non-hybrid environment. This comes also with a trick. It is possible to migrate legacy public folder to Exchange online, but it is currently not supported to migrate Exchange Server 2013 public folders. You can find HERE an extensive documentation on how to migrate legacy public folders to Exchange online and I find that this step by step description is pretty self explanatory. Please be advised that this is basically a staged migration.
A migration from legacy public folders to Exchange Server 2013 public folders is also supported. Before you decide to proceed with this type of migration, please read carefully all prerequisites. It is very important, for example, that you first move all your mailboxes to Exchange Server 2013 and afterwards the public folders. Also pay attention to the limits of the public folders in Exchange 2013 so that you are completely aware of all pros and cons and take a responsible decision.
You might ask yourself, why is it not possible to migrate from Exchange 2013 public folders? Well, as you may know public folders have been completely redesigned in Exchange 2013 and Exchange online is running on Exchange 2013. Because the new public folders design, it is currently not supported to migrate them from a modern public folders infrastructure to another modern public folder infrastructure. This also applies for an Exchange 2013 on premises to on premises migration.
Another important point to take into consideration is the behaviour of public folders in an Exchange hybrid environment. Please be aware that if you have create an Exchange hybrid, it is not possible to move the public folders with remotely, as you can do with normal mailboxes. However, public folders can coexist in a hybrid environment and will be accessible from both sides. Downside here is that you cannot have some public folders on premises and some on cloud. You would have to plan carefully ahead and decide whether you want to have your public folders on premises, or in the cloud. Once this is decided and you have set up the hybrid environment, both cloud and on premises users will be able to access the public folders that reside on premises or in the cloud.
If you have legacy on premise public folders you can also configure them to work in a hybrid deployment, following this TechNet documentation.
There is one thing you should however be aware of. If you have your public folders on Exchange Server and mailboxes on Exchange online, only MAPI clients will be able to access them. This means that the on premises public folders will be available to cloud users only with the Outlook client, but not Outlook for Mac or ActiveSync.
OK, understood. But my current business needs don’t fall in either of this scenarios. Is there a way to however migrate public folders?
Fortunately, the answer to this question is YES. However, this involves some manual work, but in smaller organizations this shouldn’t be any issue. We would have basically 2 options to do this.
1. Create a mailbox, configure the folder structure to match the public folder structure. Open this mailbox in Outlook and manually drag and drop the public folders content into that mailbox. When this is done, this mailbox can be remotely moved in a hybrid environment bot to on premises or to the cloud, depending where you want to move your public folders. Once the mailbox is moved, copy the content of the mailbox to the public folders of the destionation.
2. Migrate public folders to Sharepoint/Sharepoint Online. This process can be done manually by moving the date to Sharepoint. Alternatively there are some great third party tools that can help you to achieve this goal, like Quest.
My advise is to carefully plan and choose the scenario that matches at best the business needs. Microsoft is currently working to expand the features of the modern public folders and migration possibilities are also on the roadmap. But until we’ll be able to move modern public folders between infrastructures, we have to plan according the limitations.
Hope this helps.