Step 17 — Testing Public Folders for Users
After the migration batch has completed, you need to make a few small changes to the Exchange Online config to re-point the users to the cloud version of Public Folders. These commands are very straight forward and listed below.

Changing your org to use Exchange Online Public Folders

Now according the the TechNet article you can assign yourself (or test users) to a Public Folder mailbox and test connectivity. This is worth while just to see if you can see and expand the hierarchy, however it’s not really suitable for a good test of the service.

The reason for this? Exchange Online has a number of automated scripts and processes that are kicked off to improve performance, but these only kick in once you’ve unlocked Public Folders.

PowerShell commands on how to get and set a users Default Public Folder Mailbox

Get used to seeing this…
After you’ve given your test users a DefaultPublicFolderMailbox value, open Outlook and try expanding Public Folders — it may take up to 2 restarts of Outlook and up to 2 minutes for Public Folders to reappear.

You will most likely see this… get used to it.

Before we unlocked Public Folders for all users, the first expansion took me 18 minutes to expand the hierarchy. Subsequent restarts of Outlook did bring this number down to a few minutes.

Step 18 — Unlocking Public Folders for Users
Now you are ready to proceed, you need to unlock Public Folders for all users. This is done by marking the migration a success on your legacy Exchange servers. This process will need to replicate around, so give this time.

Unlocking Public Folders for all users

After marking this as complete, performance began to improve and within an hour, I could now expand Public Folders in Outlook within a few seconds and browse through the folder structure. As you click through the folders, there is a pause as Outlook has to connect to a new mailbox. This process can be slow at times.

Outlook Connection Status showing all Public Folders connected

Step 19 — Don’t Forget to Change your Public Folder Quota’s
Something that I overlooked was the default Public Folder quota’s, they are set at a Warning of 1.7GB and Prohibit Post of 2GB

Let’s just say we had quite a few emails that went out early Monday morning to all Public Folder owners… (whoops).