In Hybrid, clarification of Microsoft statement "Public folders can only reside in one place, so you must decide whether your public folders will be in Exchange Online or on-premises."

Question

In Hybrid, clarification of Microsoft statement "Public folders can only reside in one place, so you must decide whether your public folders will be in Exchange Online or on-premises."

Brian Hall 81

I'm planning to move some small Public Folders to O365 now that we have our Hybrid environment up and working.

Several Microsoft articles I've read say the following in regards to Public Folders in Hybrid:

"Public folders can only reside in one place, so you must decide whether your public folders will be in Exchange Online or on-premises."

That is from this article:

https://learn.microsoft.com/en-us/exchange/collaboration/public-folders/configure-legacy-public-folders-for-hybrid?view=exchserver-2019

Does that mean that if I have on premise Public Folders, I can't create any Exchange Online Public Folders at all, or does it just mean that users can only access Public Folders in one location.

I do still have my Exchange 2019 Public Folders on Exchange 2019, but Exchange Online appears to have the ability for me to create a new Exchange Online Public Folder mailbox and Public Folders while the on-prem PFs still exist.

Since the PFs are small, I'd like to just export them to a PST file, create a new Public Folder Mailbox in Exchange Online, and import the PST to Exchange Online's Public Folders while the on-prem PFs still exist, and then have online users access the new Online PFs while on prem users still access the old on-prem PFs. There won't be much time until everyone is moved Online, so I'm not worried about anything being sync'd.

Can I do it this way, or will I be blocked from having any Exchange Online PFs at all while the on-prem PFs still exist?

3 answers

Your answer

Answer 1

Andy David - MVP 157.8K MVP Volunteer Moderator

In theory, if you were to export ALL the folders on-prem to psts and then create new PF mailboxes and their folders in Exchange Online, this would work. What you lose are permissions, rules etc... because you will need to recreate that in ExO.

https://learn.microsoft.com/en-us/exchange/collaboration-exo/public-folders/create-public-folder-mailbox

The restriction is that the Outlook client can only see one tree, so if you created new PFs in Exchange online, thats what the clients would see - its an all or nothing thing - they will never see the on-prem ones. The trick would be to ensure the org config is set to -PublicFoldersEnabled Local

https://learn.microsoft.com/en-us/powershell/module/exchange/set-organizationconfig?view=exchange-ps

Having said, Most people choose to migrate them the traditional way:

https://learn.microsoft.com/en-us/exchange/collaboration/public-folders/migrate-to-exchange-online?view=exchserver-2019

Brian Hall 81 Reputation points

2023-06-28T13:19:03.75+00:00

Thank you, Andy. In our scenario, all users will be moved Online, so I won't need them to see the on premise PFs anymore. And permissions, while present, are basic enough that they can be recreated easily. We only have about 5 PF Calendars that we will be moving, and each one has only 2 or 3 Authors, with the default role set to Reviewer.

In that scenario, if I understand you correctly, I wouldn't need to use the -PublicFoldersEnabled Local command since all users will be online and won't need to see the on-premise PFs, and I could just export/import with the .PST. Is that right?

Answer 2

If you connect from an external network, ensure MAPI/http is configured and published correctly. The Autodiscover process from your Exchange Online organization will "find" the on-premises public folder mailboxes you configured in the Exchange Online Set-OrganizationConfig.

Helpful links -

https://learn.microsoft.com/en-us/exchange/collaboration-exo/public-folders/set-up-legacy-hybrid-public-folders

https://community.spiceworks.com/how_to/185867-migrate-mail-enabled-public-folders-in-hybrid-mode

Please Note: Since the web sites are not hosted by Microsoft, the links may change without notice. Microsoft does not guarantee the accuracy of this information.

Answer 3

Jarvis Sun-MSFT 10,231 Microsoft External Staff

Hi @Brian Hall ,

It is not supported that an org has public folders in both Exchange Online and On-Prem at the same time.

Even though there can be two separate PFs, Outlook can only view and access one hierarchy, so on-premises mailboxes and Exchange Online mailboxes now only see local public folders, and the migrated mailbox cannot see the organization library which hosted on Exchange online.

You can refer to this post: https://learn.microsoft.com/en-us/answers/questions/61963/hybrid-configuration-public-folders

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Brian Hall 81 Reputation points

2023-06-28T11:00:10.33+00:00

Thank you, Jarvis. After posting this, I was reading an official Microsoft Public Folder Migration document in the O365 Admin center, and it recommends to export and import Public Folders as .PST files if they are not large, which is the case for us. Here is the recommendation from the O365 Admin Center:

Migrate public folder data to Microsoft 365 If you don't have a lot of public folders to bring into Microsoft 365, the easiest way to bring them would be to copy the data into .PST files and then import them into Microsoft 365. For small amounts of data, a simple drag and drop of public folder into a .PST file can be sufficient.

If that is their recommendation, why wouldn't a migrated mailbox be able to see a PF hosted on Exchange Online? In this scenario, there is no mention of a requirement to delete or reconfigure the on-prem PFs, although I would do that. It seems that the intention of this document is to import the PF .PST file for all Exchange Online users, even if they are migrated, since the name of the document is "How to Migrate Public Folders to Exchange Online."

Here's a screenshot of the documents since it's a side panel in Admin Center and not a direct link
Jarvis Sun-MSFT 10,231 Reputation points Microsoft External Staff

2023-06-29T05:49:24.86+00:00

@Brian Hall , thanks for your information. Given your scenario, with little work, you can choose the PST migration, it should be noted that this will have some time impact on Online users, and don't forget to make a backup. Hope things going well.

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In Hybrid, clarification of Microsoft statement "Public folders can only reside in one place, so you must decide whether your public folders will be in Exchange Online or on-premises."

3 answers

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