Troubleshooting: Migrating Office 365 Public Folders

Migrating Office 365 Public Folders

Not that I expect many people to have this problem, but I learned something new today. Did you know, that if you have public folders you are moving to Office 365 that exceed 50 GB, you have to wait for Microsoft to “Auto-Split” them?

Basically what is supposed to happen is you have a public folder and as it grows close to the 50 GB limit, an automated process is kicked off that will migrate some date to a new public folder mailbox. This is seamless to the end user and allows you to continue to add data. What I was doing was migrating a very large amount of data at one time. This caused the public folder to reach the limit of 50 GB in a few days. I was not moving data slowly, so the automated process did not have time to run. Since I was in a time time, crunch I needed to find a solution.

According to Microsoft, it can take up to two weeks for this process to happen. And I didn’t have two weeks. I needed it to happen, roughly — immediately — so I knew I needed to figure something out. I thought I could just create a new public folder mailbox and that would be that. The problem is, that was not working. It was still binding me to the 50 GB limit. I read that if you create a new public folder mailbox Microsoft will use it for its auto-split process. Again this did not help me.

I did a little research and found that there were two solutions to my issue. The first was to wait the up-to-two-weeks for the automated process, and the second was to run two PowerShell commands. Of course, I opted for the PowerShell commands. Here is what I did.

First I started power shell as an administrator. Then I ran the following script to connect to Exchange online via PowerShell.

Set-ExecutionPolicy Unrestricted -Force
$LiveCred = Get-Credential
$Session = New-PSSession -ConfigurationName Microsoft.Exchange -ConnectionUri -Credential $LiveCred -Authentication Basic -AllowRedirection
Import-PSSession $Session

Once connected I then ran this command (The public folder email address can be anything you wish.):

New-Mailbox -PublicFolder -Name MasterHierarchy

Once that was complete I ran this command (Again the name can be anything you wish.):

New-PublicFolder -Name PF201 -Mailbox SecondaryPFMbx

Once the commands were complete I had a new folder under my public folders. In the Exchange management console, in the Office 365 public folder mailboxes I had a new 50 GB limit. I was now able to start moving more data and effectively had a 100 GB limit to now use.

I hope you have found this helpful. If you have any questions, please feel free to post them below. Also, make sure you follow and friend us through social media at Twitter or Facebook.

Ryan Ash


Ryan Ash
Network Consultant




©Custom Systems Corporation 2015


2 thoughts on “Troubleshooting: Migrating Office 365 Public Folders

  1. Hi Ryan, I’m doing this right now on a 200+ GB public folder. Can I ask how does this splitting impact the end result to the user in Outlook/OWA? It is the exact same single root public folder view as before the migration or am I going to end up seeing several different root public folders with all the data copied in randomly to different ones?

    • John,

      It depends on how fast you need to move the data to Exchange Online. If you can move roughly 48 GB of data to the public folder that you create and then wait between two days and two weeks for the auto split to happen, where it gives you a new mailbox (continuing that process until all the data is moved) then yes, you would be able to have one folder that I assume would contain sub folders. I will guess you do not have two months to move this data so the answer is no, you would not have one root folder, but here is how it worked out for me. This way allows you to move data much faster and still keep the hierarchy from looking messy.
      I moved close to 100 GB of data when I ran into this issue. What I now have when using Outlook to view public folders is…One line that says public folders. When I expand that I get the “All Public Folders” tab. These two are what you would always see in Outlook. Now under that I have three folders that separate the data that I moved. This is where you would not have one folder but most likely five in your case. Basically each one can hold 50 GB unless you wait for Microsoft to complete the auto split (which cannot be forced). You can have as many sub folders under each of them as you like. In my case there are hundreds under each.
      As for where the data is, that depends on how you are migrating. In my case, I had exported the folders and then was importing them so I was able to choose which of the three main folders under “All Public Folders” they would go too. It is a time consuming process since you can only move one folder at a time (which can include sub folders).
      As for OWA, to me it is not that easy to use Public Folders this way. In my case, where I have sub folders that may go five or six levels deep, I need to dig all the way in to the exact sub folder I want and then add that to the Favorites in Outlook just to view it. Public Folders in OWA are almost not worth using unless there is just one or even a few specific ones you need. Outlook makes using them much easier.
      Have you considered moving the data to SharePoint instead?
      Please let me know if I failed to answer your question or if you have others.

Leave a Reply

Your email address will not be published. Required fields are marked *